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  <title>Changes</title>

  <para>The following chapters document the evolution of the V4L2 API,
errata or extensions. They are also intended to help application and
driver writers to port or update their code.</para>

  <section id="diff-v4l">
    <title>Differences between V4L and V4L2</title>

    <para>The Video For Linux API was first introduced in Linux 2.1 to
unify and replace various TV and radio device related interfaces,
developed independently by driver writers in prior years. Starting
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with Linux 2.5 the much improved V4L2 API replaces the V4L API.
The support for the old V4L calls were removed from Kernel, but the
library <xref linkend="libv4l" /> supports the conversion of a V4L
API system call into a V4L2 one.</para>
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    <section>
      <title>Opening and Closing Devices</title>

      <para>For compatibility reasons the character device file names
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recommended for V4L2 video capture, overlay, radio and raw
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vbi capture devices did not change from those used by V4L. They are
listed in <xref linkend="devices" /> and below in <xref
	  linkend="v4l-dev" />.</para>

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      <para>The teletext devices (minor range 192-223) have been removed in
V4L2 and no longer exist. There is no hardware available anymore for handling
pure teletext. Instead raw or sliced VBI is used.</para>

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      <para>The V4L <filename>videodev</filename> module automatically
assigns minor numbers to drivers in load order, depending on the
registered device type. We recommend that V4L2 drivers by default
register devices with the same numbers, but the system administrator
can assign arbitrary minor numbers using driver module options. The
major device number remains 81.</para>

      <table id="v4l-dev">
	<title>V4L Device Types, Names and Numbers</title>
	<tgroup cols="3">
	  <thead>
	    <row>
	      <entry>Device Type</entry>
	      <entry>File Name</entry>
	      <entry>Minor Numbers</entry>
	    </row>
	  </thead>
	  <tbody valign="top">
	    <row>
	      <entry>Video capture and overlay</entry>
	      <entry><para><filename>/dev/video</filename> and
<filename>/dev/bttv0</filename><footnote> <para>According to
Documentation/devices.txt these should be symbolic links to
<filename>/dev/video0</filename>. Note the original bttv interface is
not compatible with V4L or V4L2.</para> </footnote>,
<filename>/dev/video0</filename> to
<filename>/dev/video63</filename></para></entry>
	      <entry>0-63</entry>
	    </row>
	    <row>
	      <entry>Radio receiver</entry>
	      <entry><para><filename>/dev/radio</filename><footnote>
		    <para>According to
<filename>Documentation/devices.txt</filename> a symbolic link to
<filename>/dev/radio0</filename>.</para>
		  </footnote>, <filename>/dev/radio0</filename> to
<filename>/dev/radio63</filename></para></entry>
	      <entry>64-127</entry>
	    </row>
	    <row>
	      <entry>Raw VBI capture</entry>
	      <entry><para><filename>/dev/vbi</filename>,
<filename>/dev/vbi0</filename> to
<filename>/dev/vbi31</filename></para></entry>
	      <entry>224-255</entry>
	    </row>
	  </tbody>
	</tgroup>
      </table>

      <para>V4L prohibits (or used to prohibit) multiple opens of a
device file. V4L2 drivers <emphasis>may</emphasis> support multiple
opens, see <xref linkend="open" /> for details and consequences.</para>

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      <para>V4L drivers respond to V4L2 ioctls with an &EINVAL;.</para>
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    </section>

    <section>
      <title>Querying Capabilities</title>

      <para>The V4L <constant>VIDIOCGCAP</constant> ioctl is
equivalent to V4L2's &VIDIOC-QUERYCAP;.</para>

      <para>The <structfield>name</structfield> field in struct
<structname>video_capability</structname> became
<structfield>card</structfield> in &v4l2-capability;,
<structfield>type</structfield> was replaced by
<structfield>capabilities</structfield>. Note V4L2 does not
distinguish between device types like this, better think of basic
video input, video output and radio devices supporting a set of
related functions like video capturing, video overlay and VBI
capturing. See <xref linkend="open" /> for an
introduction.<informaltable>
	  <tgroup cols="3">
	    <thead>
	      <row>
		<entry>struct
<structname>video_capability</structname>
<structfield>type</structfield></entry>
		<entry>&v4l2-capability;
<structfield>capabilities</structfield> flags</entry>
		<entry>Purpose</entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry><constant>VID_TYPE_CAPTURE</constant></entry>
		<entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
		<entry>The <link linkend="capture">video
capture</link> interface is supported.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_TUNER</constant></entry>
		<entry><constant>V4L2_CAP_TUNER</constant></entry>
		<entry>The device has a <link linkend="tuner">tuner or
modulator</link>.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_TELETEXT</constant></entry>
		<entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
		<entry>The <link linkend="raw-vbi">raw VBI
capture</link> interface is supported.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_OVERLAY</constant></entry>
		<entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
		<entry>The <link linkend="overlay">video
overlay</link> interface is supported.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_CHROMAKEY</constant></entry>
		<entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant> in
field <structfield>capability</structfield> of
&v4l2-framebuffer;</entry>
		<entry>Whether chromakey overlay is supported. For
more information on overlay see
<xref linkend="overlay" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_CLIPPING</constant></entry>
		<entry><constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant>
and <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant> in field
<structfield>capability</structfield> of &v4l2-framebuffer;</entry>
		<entry>Whether clipping the overlaid image is
supported, see <xref linkend="overlay" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_FRAMERAM</constant></entry>
		<entry><constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant>
<emphasis>not set</emphasis> in field
<structfield>capability</structfield> of &v4l2-framebuffer;</entry>
		<entry>Whether overlay overwrites frame buffer memory,
see <xref linkend="overlay" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_SCALES</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>This flag indicates if the hardware can scale
images. The V4L2 API implies the scale factor by setting the cropping
dimensions and image size with the &VIDIOC-S-CROP; and &VIDIOC-S-FMT;
ioctl, respectively. The driver returns the closest sizes possible.
For more information on cropping and scaling see <xref
		    linkend="crop" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_MONOCHROME</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>Applications can enumerate the supported image
formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device
supports grey scale capturing only. For more information on image
formats see <xref linkend="pixfmt" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_SUBCAPTURE</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>Applications can call the &VIDIOC-G-CROP; ioctl
to determine if the device supports capturing a subsection of the full
picture ("cropping" in V4L2). If not, the ioctl returns the &EINVAL;.
For more information on cropping and scaling see <xref
		    linkend="crop" />.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_MPEG_DECODER</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>Applications can enumerate the supported image
formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device
supports MPEG streams.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_MPEG_ENCODER</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>See above.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_MJPEG_DECODER</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>See above.</entry>
	      </row>
	      <row>
		<entry><constant>VID_TYPE_MJPEG_ENCODER</constant></entry>
		<entry><constant>-</constant></entry>
		<entry>See above.</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable></para>

      <para>The <structfield>audios</structfield> field was replaced
by <structfield>capabilities</structfield> flag
<constant>V4L2_CAP_AUDIO</constant>, indicating
<emphasis>if</emphasis> the device has any audio inputs or outputs. To
determine their number applications can enumerate audio inputs with
the &VIDIOC-G-AUDIO; ioctl. The audio ioctls are described in <xref
	  linkend="audio" />.</para>

      <para>The <structfield>maxwidth</structfield>,
<structfield>maxheight</structfield>,
<structfield>minwidth</structfield> and
<structfield>minheight</structfield> fields were removed. Calling the
&VIDIOC-S-FMT; or &VIDIOC-TRY-FMT; ioctl with the desired dimensions
returns the closest size possible, taking into account the current
video standard, cropping and scaling limitations.</para>
    </section>

    <section>
      <title>Video Sources</title>

      <para>V4L provides the <constant>VIDIOCGCHAN</constant> and
<constant>VIDIOCSCHAN</constant> ioctl using struct
<structname>video_channel</structname> to enumerate
the video inputs of a V4L device. The equivalent V4L2 ioctls
are &VIDIOC-ENUMINPUT;, &VIDIOC-G-INPUT; and &VIDIOC-S-INPUT;
using &v4l2-input; as discussed in <xref linkend="video" />.</para>

      <para>The <structfield>channel</structfield> field counting
inputs was renamed to <structfield>index</structfield>, the video
input types were renamed as follows: <informaltable>
	  <tgroup cols="2">
	    <thead>
	      <row>
		<entry>struct <structname>video_channel</structname>
<structfield>type</structfield></entry>
		<entry>&v4l2-input;
<structfield>type</structfield></entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry><constant>VIDEO_TYPE_TV</constant></entry>
		<entry><constant>V4L2_INPUT_TYPE_TUNER</constant></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_TYPE_CAMERA</constant></entry>
		<entry><constant>V4L2_INPUT_TYPE_CAMERA</constant></entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable></para>

      <para>Unlike the <structfield>tuners</structfield> field
expressing the number of tuners of this input, V4L2 assumes each video
input is connected to at most one tuner. However a tuner can have more
than one input, &ie; RF connectors, and a device can have multiple
tuners. The index number of the tuner associated with the input, if
any, is stored in field <structfield>tuner</structfield> of
&v4l2-input;. Enumeration of tuners is discussed in <xref
	  linkend="tuner" />.</para>

      <para>The redundant <constant>VIDEO_VC_TUNER</constant> flag was
dropped. Video inputs associated with a tuner are of type
<constant>V4L2_INPUT_TYPE_TUNER</constant>. The
<constant>VIDEO_VC_AUDIO</constant> flag was replaced by the
<structfield>audioset</structfield> field. V4L2 considers devices with
up to 32 audio inputs. Each set bit in the
<structfield>audioset</structfield> field represents one audio input
this video input combines with. For information about audio inputs and
how to switch between them see <xref linkend="audio" />.</para>

      <para>The <structfield>norm</structfield> field describing the
supported video standards was replaced by
<structfield>std</structfield>. The V4L specification mentions a flag
<constant>VIDEO_VC_NORM</constant> indicating whether the standard can
be changed. This flag was a later addition together with the
<structfield>norm</structfield> field and has been removed in the
meantime. V4L2 has a similar, albeit more comprehensive approach
to video standards, see <xref linkend="standard" /> for more
information.</para>
    </section>

    <section>
      <title>Tuning</title>

      <para>The V4L <constant>VIDIOCGTUNER</constant> and
<constant>VIDIOCSTUNER</constant> ioctl and struct
<structname>video_tuner</structname> can be used to enumerate the
tuners of a V4L TV or radio device. The equivalent V4L2 ioctls are
&VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; using &v4l2-tuner;. Tuners are
covered in <xref linkend="tuner" />.</para>

      <para>The <structfield>tuner</structfield> field counting tuners
was renamed to <structfield>index</structfield>. The fields
<structfield>name</structfield>, <structfield>rangelow</structfield>
and <structfield>rangehigh</structfield> remained unchanged.</para>

      <para>The <constant>VIDEO_TUNER_PAL</constant>,
<constant>VIDEO_TUNER_NTSC</constant> and
<constant>VIDEO_TUNER_SECAM</constant> flags indicating the supported
video standards were dropped. This information is now contained in the
associated &v4l2-input;. No replacement exists for the
<constant>VIDEO_TUNER_NORM</constant> flag indicating whether the
video standard can be switched. The <structfield>mode</structfield>
field to select a different video standard was replaced by a whole new
set of ioctls and structures described in <xref linkend="standard" />.
Due to its ubiquity it should be mentioned the BTTV driver supports
several standards in addition to the regular
<constant>VIDEO_MODE_PAL</constant> (0),
<constant>VIDEO_MODE_NTSC</constant>,
<constant>VIDEO_MODE_SECAM</constant> and
<constant>VIDEO_MODE_AUTO</constant> (3). Namely N/PAL Argentina,
M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic).</para>

      <para>The <constant>VIDEO_TUNER_STEREO_ON</constant> flag
indicating stereo reception became
<constant>V4L2_TUNER_SUB_STEREO</constant> in field
<structfield>rxsubchans</structfield>. This field also permits the
detection of monaural and bilingual audio, see the definition of
&v4l2-tuner; for details. Presently no replacement exists for the
<constant>VIDEO_TUNER_RDS_ON</constant> and
<constant>VIDEO_TUNER_MBS_ON</constant> flags.</para>

      <para> The <constant>VIDEO_TUNER_LOW</constant> flag was renamed
to <constant>V4L2_TUNER_CAP_LOW</constant> in the &v4l2-tuner;
<structfield>capability</structfield> field.</para>

      <para>The <constant>VIDIOCGFREQ</constant> and
<constant>VIDIOCSFREQ</constant> ioctl to change the tuner frequency
where renamed to &VIDIOC-G-FREQUENCY; and  &VIDIOC-S-FREQUENCY;. They
take a pointer to a &v4l2-frequency; instead of an unsigned long
integer.</para>
    </section>

    <section id="v4l-image-properties">
      <title>Image Properties</title>

      <para>V4L2 has no equivalent of the
<constant>VIDIOCGPICT</constant> and <constant>VIDIOCSPICT</constant>
ioctl and struct <structname>video_picture</structname>. The following
fields where replaced by V4L2 controls accessible with the
&VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls:<informaltable>
	  <tgroup cols="2">
	    <thead>
	      <row>
		<entry>struct <structname>video_picture</structname></entry>
		<entry>V4L2 Control ID</entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry><structfield>brightness</structfield></entry>
		<entry><constant>V4L2_CID_BRIGHTNESS</constant></entry>
	      </row>
	      <row>
		<entry><structfield>hue</structfield></entry>
		<entry><constant>V4L2_CID_HUE</constant></entry>
	      </row>
	      <row>
		<entry><structfield>colour</structfield></entry>
		<entry><constant>V4L2_CID_SATURATION</constant></entry>
	      </row>
	      <row>
		<entry><structfield>contrast</structfield></entry>
		<entry><constant>V4L2_CID_CONTRAST</constant></entry>
	      </row>
	      <row>
		<entry><structfield>whiteness</structfield></entry>
		<entry><constant>V4L2_CID_WHITENESS</constant></entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable></para>

      <para>The V4L picture controls are assumed to range from 0 to
65535 with no particular reset value. The V4L2 API permits arbitrary
limits and defaults which can be queried with the &VIDIOC-QUERYCTRL;
ioctl. For general information about controls see <xref
linkend="control" />.</para>

      <para>The <structfield>depth</structfield> (average number of
bits per pixel) of a video image is implied by the selected image
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format. V4L2 does not explicitly provide such information assuming
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applications recognizing the format are aware of the image depth and
others need not know. The <structfield>palette</structfield> field
moved into the &v4l2-pix-format;:<informaltable>
	  <tgroup cols="2">
	    <thead>
	      <row>
		<entry>struct <structname>video_picture</structname>
<structfield>palette</structfield></entry>
		<entry>&v4l2-pix-format;
<structfield>pixfmt</structfield></entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry><constant>VIDEO_PALETTE_GREY</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-GREY"><constant>V4L2_PIX_FMT_GREY</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_HI240</constant></entry>
		<entry><para><link
linkend="pixfmt-reserved"><constant>V4L2_PIX_FMT_HI240</constant></link><footnote>
		      <para>This is a custom format used by the BTTV
driver, not one of the V4L2 standard formats.</para>
		    </footnote></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_RGB565</constant></entry>
		<entry><para><link
linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB565</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_RGB555</constant></entry>
		<entry><para><link
linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB555</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_RGB24</constant></entry>
		<entry><para><link
linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR24</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_RGB32</constant></entry>
		<entry><para><link
linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR32</constant></link><footnote>
		      <para>Presumably all V4L RGB formats are
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little-endian, although some drivers might interpret them according to machine endianness. V4L2 defines little-endian, big-endian and red/blue
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swapped variants. For details see <xref linkend="pixfmt-rgb" />.</para>
		    </footnote></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV422</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry>
	      </row>
	      <row>
		<entry><para><constant>VIDEO_PALETTE_YUYV</constant><footnote>
		      <para><constant>VIDEO_PALETTE_YUV422</constant>
and <constant>VIDEO_PALETTE_YUYV</constant> are the same formats. Some
V4L drivers respond to one, some to the other.</para>
		    </footnote></para></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_UYVY</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-UYVY"><constant>V4L2_PIX_FMT_UYVY</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV420</constant></entry>
		<entry>None</entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV411</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-Y41P"><constant>V4L2_PIX_FMT_Y41P</constant></link><footnote>
		      <para>Not to be confused with
<constant>V4L2_PIX_FMT_YUV411P</constant>, which is a planar
format.</para> </footnote></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_RAW</constant></entry>
		<entry><para>None<footnote> <para>V4L explains this
as: "RAW capture (BT848)"</para> </footnote></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV422P</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YUV422P"><constant>V4L2_PIX_FMT_YUV422P</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV411P</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YUV411P"><constant>V4L2_PIX_FMT_YUV411P</constant></link><footnote>
		      <para>Not to be confused with
<constant>V4L2_PIX_FMT_Y41P</constant>, which is a packed
format.</para> </footnote></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV420P</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></link></para></entry>
	      </row>
	      <row>
		<entry><constant>VIDEO_PALETTE_YUV410P</constant></entry>
		<entry><para><link
linkend="V4L2-PIX-FMT-YVU410"><constant>V4L2_PIX_FMT_YVU410</constant></link></para></entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable></para>

      <para>V4L2 image formats are defined in <xref
linkend="pixfmt" />. The image format can be selected with the
&VIDIOC-S-FMT; ioctl.</para>
    </section>

    <section>
      <title>Audio</title>

      <para>The <constant>VIDIOCGAUDIO</constant> and
<constant>VIDIOCSAUDIO</constant> ioctl and struct
<structname>video_audio</structname> are used to enumerate the
audio inputs of a V4L device. The equivalent V4L2 ioctls are
&VIDIOC-G-AUDIO; and &VIDIOC-S-AUDIO; using &v4l2-audio; as
discussed in <xref linkend="audio" />.</para>

      <para>The <structfield>audio</structfield> "channel number"
field counting audio inputs was renamed to
<structfield>index</structfield>.</para>

      <para>On <constant>VIDIOCSAUDIO</constant> the
<structfield>mode</structfield> field selects <emphasis>one</emphasis>
of the <constant>VIDEO_SOUND_MONO</constant>,
<constant>VIDEO_SOUND_STEREO</constant>,
<constant>VIDEO_SOUND_LANG1</constant> or
<constant>VIDEO_SOUND_LANG2</constant> audio demodulation modes. When
the current audio standard is BTSC
<constant>VIDEO_SOUND_LANG2</constant> refers to SAP and
<constant>VIDEO_SOUND_LANG1</constant> is meaningless. Also
undocumented in the V4L specification, there is no way to query the
selected mode. On <constant>VIDIOCGAUDIO</constant> the driver returns
the <emphasis>actually received</emphasis> audio programmes in this
field. In the V4L2 API this information is stored in the &v4l2-tuner;
<structfield>rxsubchans</structfield> and
<structfield>audmode</structfield> fields, respectively. See <xref
linkend="tuner" /> for more information on tuners. Related to audio
modes &v4l2-audio; also reports if this is a mono or stereo
input, regardless if the source is a tuner.</para>

      <para>The following fields where replaced by V4L2 controls
accessible with the &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and
&VIDIOC-S-CTRL; ioctls:<informaltable>
	  <tgroup cols="2">
	    <thead>
	      <row>
		<entry>struct
<structname>video_audio</structname></entry>
		<entry>V4L2 Control ID</entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry><structfield>volume</structfield></entry>
		<entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry>
	      </row>
	      <row>
		<entry><structfield>bass</structfield></entry>
		<entry><constant>V4L2_CID_AUDIO_BASS</constant></entry>
	      </row>
	      <row>
		<entry><structfield>treble</structfield></entry>
		<entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry>
	      </row>
	      <row>
		<entry><structfield>balance</structfield></entry>
		<entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable></para>

      <para>To determine which of these controls are supported by a
driver V4L provides the <structfield>flags</structfield>
<constant>VIDEO_AUDIO_VOLUME</constant>,
<constant>VIDEO_AUDIO_BASS</constant>,
<constant>VIDEO_AUDIO_TREBLE</constant> and
<constant>VIDEO_AUDIO_BALANCE</constant>. In the V4L2 API the
&VIDIOC-QUERYCTRL; ioctl reports if the respective control is
supported. Accordingly the <constant>VIDEO_AUDIO_MUTABLE</constant>
and <constant>VIDEO_AUDIO_MUTE</constant> flags where replaced by the
boolean <constant>V4L2_CID_AUDIO_MUTE</constant> control.</para>

      <para>All V4L2 controls have a <structfield>step</structfield>
attribute replacing the struct <structname>video_audio</structname>
<structfield>step</structfield> field. The V4L audio controls are
assumed to range from 0 to 65535 with no particular reset value. The
V4L2 API permits arbitrary limits and defaults which can be queried
with the &VIDIOC-QUERYCTRL; ioctl. For general information about
controls see <xref linkend="control" />.</para>
    </section>

    <section>
      <title>Frame Buffer Overlay</title>

      <para>The V4L2 ioctls equivalent to
<constant>VIDIOCGFBUF</constant> and <constant>VIDIOCSFBUF</constant>
are &VIDIOC-G-FBUF; and &VIDIOC-S-FBUF;. The
<structfield>base</structfield> field of struct
<structname>video_buffer</structname> remained unchanged, except V4L2
defines a flag to indicate non-destructive overlays instead of a
<constant>NULL</constant> pointer. All other fields moved into the
&v4l2-pix-format; <structfield>fmt</structfield> substructure of
&v4l2-framebuffer;. The <structfield>depth</structfield> field was
replaced by <structfield>pixelformat</structfield>. See <xref
	  linkend="pixfmt-rgb" /> for a list of RGB formats and their
respective color depths.</para>

      <para>Instead of the special ioctls
<constant>VIDIOCGWIN</constant> and <constant>VIDIOCSWIN</constant>
V4L2 uses the general-purpose data format negotiation ioctls
&VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a
&v4l2-format; as argument. Here the <structfield>win</structfield>
member of the <structfield>fmt</structfield> union is used, a
&v4l2-window;.</para>

      <para>The <structfield>x</structfield>,
<structfield>y</structfield>, <structfield>width</structfield> and
<structfield>height</structfield> fields of struct
<structname>video_window</structname> moved into &v4l2-rect;
substructure <structfield>w</structfield> of struct
<structname>v4l2_window</structname>. The
<structfield>chromakey</structfield>,
<structfield>clips</structfield>, and
<structfield>clipcount</structfield> fields remained unchanged. Struct
<structname>video_clip</structname> was renamed to &v4l2-clip;, also
containing a struct <structname>v4l2_rect</structname>, but the
semantics are still the same.</para>

      <para>The <constant>VIDEO_WINDOW_INTERLACE</constant> flag was
dropped. Instead applications must set the
<structfield>field</structfield> field to
<constant>V4L2_FIELD_ANY</constant> or
<constant>V4L2_FIELD_INTERLACED</constant>. The
<constant>VIDEO_WINDOW_CHROMAKEY</constant> flag moved into
&v4l2-framebuffer;, under the new name
<constant>V4L2_FBUF_FLAG_CHROMAKEY</constant>.</para>

      <para>In V4L, storing a bitmap pointer in
<structfield>clips</structfield> and setting
<structfield>clipcount</structfield> to
<constant>VIDEO_CLIP_BITMAP</constant> (-1) requests bitmap
clipping, using a fixed size bitmap of 1024 &times; 625 bits. Struct
<structname>v4l2_window</structname> has a separate
<structfield>bitmap</structfield> pointer field for this purpose and
the bitmap size is determined by <structfield>w.width</structfield> and
<structfield>w.height</structfield>.</para>

      <para>The <constant>VIDIOCCAPTURE</constant> ioctl to enable or
disable overlay was renamed to &VIDIOC-OVERLAY;.</para>
    </section>

    <section>
      <title>Cropping</title>

      <para>To capture only a subsection of the full picture V4L
defines the <constant>VIDIOCGCAPTURE</constant> and
<constant>VIDIOCSCAPTURE</constant> ioctls using struct
<structname>video_capture</structname>. The equivalent V4L2 ioctls are
&VIDIOC-G-CROP; and &VIDIOC-S-CROP; using &v4l2-crop;, and the related
&VIDIOC-CROPCAP; ioctl. This is a rather complex matter, see
<xref linkend="crop" /> for details.</para>

      <para>The <structfield>x</structfield>,
<structfield>y</structfield>, <structfield>width</structfield> and
<structfield>height</structfield> fields moved into &v4l2-rect;
substructure <structfield>c</structfield> of struct
<structname>v4l2_crop</structname>. The
<structfield>decimation</structfield> field was dropped. In the V4L2
API the scaling factor is implied by the size of the cropping
rectangle and the size of the captured or overlaid image.</para>

      <para>The <constant>VIDEO_CAPTURE_ODD</constant>
and <constant>VIDEO_CAPTURE_EVEN</constant> flags to capture only the
odd or even field, respectively, were replaced by
<constant>V4L2_FIELD_TOP</constant> and
<constant>V4L2_FIELD_BOTTOM</constant> in the field named
<structfield>field</structfield> of &v4l2-pix-format; and
&v4l2-window;. These structures are used to select a capture or
overlay format with the &VIDIOC-S-FMT; ioctl.</para>
    </section>

    <section>
      <title>Reading Images, Memory Mapping</title>

      <section>
	<title>Capturing using the read method</title>

	<para>There is no essential difference between reading images
from a V4L or V4L2 device using the &func-read; function, however V4L2
drivers are not required to support this I/O method. Applications can
determine if the function is available with the &VIDIOC-QUERYCAP;
ioctl. All V4L2 devices exchanging data with applications must support
the &func-select; and &func-poll; functions.</para>

	<para>To select an image format and size, V4L provides the
<constant>VIDIOCSPICT</constant> and <constant>VIDIOCSWIN</constant>
ioctls. V4L2 uses the general-purpose data format negotiation ioctls
&VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a
&v4l2-format; as argument, here the &v4l2-pix-format; named
<structfield>pix</structfield> of its <structfield>fmt</structfield>
union is used.</para>

	<para>For more information about the V4L2 read interface see
<xref linkend="rw" />.</para>
      </section>
      <section>
	<title>Capturing using memory mapping</title>

	<para>Applications can read from V4L devices by mapping
buffers in device memory, or more often just buffers allocated in
DMA-able system memory, into their address space. This avoids the data
copying overhead of the read method. V4L2 supports memory mapping as
well, with a few differences.</para>

	<informaltable>
	  <tgroup cols="2">
	    <thead>
	      <row>
		<entry>V4L</entry>
		<entry>V4L2</entry>
	      </row>
	    </thead>
	    <tbody valign="top">
	      <row>
		<entry></entry>
		<entry>The image format must be selected before
buffers are allocated, with the &VIDIOC-S-FMT; ioctl. When no format
is selected the driver may use the last, possibly by another
application requested format.</entry>
	      </row>
	      <row>
		<entry><para>Applications cannot change the number of
buffers. The it is built into the driver, unless it has a module
option to change the number when the driver module is
loaded.</para></entry>
		<entry><para>The &VIDIOC-REQBUFS; ioctl allocates the
desired number of buffers, this is a required step in the initialization
sequence.</para></entry>
	      </row>
	      <row>
		<entry><para>Drivers map all buffers as one contiguous
range of memory. The <constant>VIDIOCGMBUF</constant> ioctl is
available to query the number of buffers, the offset of each buffer
from the start of the virtual file, and the overall amount of memory
used, which can be used as arguments for the &func-mmap;
function.</para></entry>
		<entry><para>Buffers are individually mapped. The
offset and size of each buffer can be determined with the
&VIDIOC-QUERYBUF; ioctl.</para></entry>
	      </row>
	      <row>
		<entry><para>The <constant>VIDIOCMCAPTURE</constant>
ioctl prepares a buffer for capturing. It also determines the image
format for this buffer. The ioctl returns immediately, eventually with
an &EAGAIN; if no video signal had been detected. When the driver
supports more than one buffer applications can call the ioctl multiple
times and thus have multiple outstanding capture
requests.</para><para>The <constant>VIDIOCSYNC</constant> ioctl
suspends execution until a particular buffer has been
filled.</para></entry>
		<entry><para>Drivers maintain an incoming and outgoing
queue. &VIDIOC-QBUF; enqueues any empty buffer into the incoming
queue. Filled buffers are dequeued from the outgoing queue with the
&VIDIOC-DQBUF; ioctl. To wait until filled buffers become available this
function, &func-select; or &func-poll; can be used. The
&VIDIOC-STREAMON; ioctl must be called once after enqueuing one or
more buffers to start capturing. Its counterpart
&VIDIOC-STREAMOFF; stops capturing and dequeues all buffers from both
queues. Applications can query the signal status, if known, with the
&VIDIOC-ENUMINPUT; ioctl.</para></entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>

	<para>For a more in-depth discussion of memory mapping and
examples, see <xref linkend="mmap" />.</para>
      </section>
    </section>

    <section>
      <title>Reading Raw VBI Data</title>

      <para>Originally the V4L API did not specify a raw VBI capture
interface, only the device file <filename>/dev/vbi</filename> was
reserved for this purpose. The only driver supporting this interface
was the BTTV driver, de-facto defining the V4L VBI interface. Reading
from the device yields a raw VBI image with the following
parameters:<informaltable>
	    <tgroup cols="2">
	      <thead>
		<row>
		  <entry>&v4l2-vbi-format;</entry>
		  <entry>V4L, BTTV driver</entry>
		</row>
	      </thead>
	      <tbody valign="top">
		<row>
		  <entry>sampling_rate</entry>
		  <entry>28636363&nbsp;Hz NTSC (or any other 525-line
standard); 35468950&nbsp;Hz PAL and SECAM (625-line standards)</entry>
		</row>
		<row>
		  <entry>offset</entry>
		  <entry>?</entry>
		</row>
		<row>
		  <entry>samples_per_line</entry>
		  <entry>2048</entry>
		</row>
		<row>
		  <entry>sample_format</entry>
		  <entry>V4L2_PIX_FMT_GREY. The last four bytes (a
826
machine endianness integer) contain a frame counter.</entry>
827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083
		</row>
		<row>
		  <entry>start[]</entry>
		  <entry>10, 273 NTSC; 22, 335 PAL and SECAM</entry>
		</row>
		<row>
		  <entry>count[]</entry>
		  <entry><para>16, 16<footnote><para>Old driver
versions used different values, eventually the custom
<constant>BTTV_VBISIZE</constant> ioctl was added to query the
correct values.</para></footnote></para></entry>
		</row>
		<row>
		  <entry>flags</entry>
		  <entry>0</entry>
		</row>
	      </tbody>
	    </tgroup>
	</informaltable></para>

      <para>Undocumented in the V4L specification, in Linux 2.3 the
<constant>VIDIOCGVBIFMT</constant> and
<constant>VIDIOCSVBIFMT</constant> ioctls using struct
<structname>vbi_format</structname> were added to determine the VBI
image parameters. These ioctls are only partially compatible with the
V4L2 VBI interface specified in <xref linkend="raw-vbi" />.</para>

      <para>An <structfield>offset</structfield> field does not
exist, <structfield>sample_format</structfield> is supposed to be
<constant>VIDEO_PALETTE_RAW</constant>, equivalent to
<constant>V4L2_PIX_FMT_GREY</constant>. The remaining fields are
probably equivalent to &v4l2-vbi-format;.</para>

      <para>Apparently only the Zoran (ZR 36120) driver implements
these ioctls. The semantics differ from those specified for V4L2 in two
ways. The parameters are reset on &func-open; and
<constant>VIDIOCSVBIFMT</constant> always returns an &EINVAL; if the
parameters are invalid.</para>
    </section>

    <section>
      <title>Miscellaneous</title>

      <para>V4L2 has no equivalent of the
<constant>VIDIOCGUNIT</constant> ioctl. Applications can find the VBI
device associated with a video capture device (or vice versa) by
reopening the device and requesting VBI data. For details see
<xref linkend="open" />.</para>

      <para>No replacement exists for <constant>VIDIOCKEY</constant>,
and the V4L functions for microcode programming. A new interface for
MPEG compression and playback devices is documented in <xref
	  linkend="extended-controls" />.</para>
    </section>

  </section>

  <section id="hist-v4l2">
    <title>Changes of the V4L2 API</title>

    <para>Soon after the V4L API was added to the kernel it was
criticised as too inflexible. In August 1998 Bill Dirks proposed a
number of improvements and began to work on documentation, example
drivers and applications. With the help of other volunteers this
eventually became the V4L2 API, not just an extension but a
replacement for the V4L API. However it took another four years and
two stable kernel releases until the new API was finally accepted for
inclusion into the kernel in its present form.</para>

    <section>
      <title>Early Versions</title>
      <para>1998-08-20: First version.</para>

      <para>1998-08-27: The &func-select; function was introduced.</para>

      <para>1998-09-10: New video standard interface.</para>

      <para>1998-09-18: The <constant>VIDIOC_NONCAP</constant> ioctl
was replaced by the otherwise meaningless <constant>O_TRUNC</constant>
&func-open; flag, and the aliases <constant>O_NONCAP</constant> and
<constant>O_NOIO</constant> were defined. Applications can set this
flag if they intend to access controls only, as opposed to capture
applications which need exclusive access. The
<constant>VIDEO_STD_XXX</constant> identifiers are now ordinals
instead of flags, and the <function>video_std_construct()</function>
helper function takes id and transmission arguments.</para>

      <para>1998-09-28: Revamped video standard. Made video controls
individually enumerable.</para>

      <para>1998-10-02: The <structfield>id</structfield> field was
removed from struct <structname>video_standard</structname> and the
color subcarrier fields were renamed. The &VIDIOC-QUERYSTD; ioctl was
renamed to &VIDIOC-ENUMSTD;, &VIDIOC-G-INPUT; to &VIDIOC-ENUMINPUT;. A
first draft of the Codec API was released.</para>

      <para>1998-11-08: Many minor changes. Most symbols have been
renamed. Some material changes to &v4l2-capability;.</para>

      <para>1998-11-12: The read/write directon of some ioctls was misdefined.</para>

      <para>1998-11-14: <constant>V4L2_PIX_FMT_RGB24</constant>
changed to <constant>V4L2_PIX_FMT_BGR24</constant>, and
<constant>V4L2_PIX_FMT_RGB32</constant> changed to
<constant>V4L2_PIX_FMT_BGR32</constant>. Audio controls are now
accessible with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls under
names starting with <constant>V4L2_CID_AUDIO</constant>. The
<constant>V4L2_MAJOR</constant> define was removed from
<filename>videodev.h</filename> since it was only used once in the
<filename>videodev</filename> kernel module. The
<constant>YUV422</constant> and <constant>YUV411</constant> planar
image formats were added.</para>

      <para>1998-11-28: A few ioctl symbols changed. Interfaces for codecs and
video output devices were added.</para>

      <para>1999-01-14: A raw VBI capture interface was added.</para>

      <para>1999-01-19: The <constant>VIDIOC_NEXTBUF</constant> ioctl
      was removed.</para>
    </section>

    <section>
      <title>V4L2 Version 0.16 1999-01-31</title>
      <para>1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF
are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added
digital zoom (cropping) controls.</para>
    </section>

    <!-- Where's 0.17? mhs couldn't find that videodev.h, perhaps Bill
	 forgot to bump the version number or never released it. -->

    <section>
      <title>V4L2 Version 0.18 1999-03-16</title>
      <para>Added a v4l to V4L2 ioctl compatibility layer to
videodev.c. Driver writers, this changes how you implement your ioctl
handler. See the Driver Writer's Guide. Added some more control id
codes.</para>
    </section>

    <section>
      <title>V4L2 Version 0.19 1999-06-05</title>
      <para>1999-03-18: Fill in the category and catname fields of
v4l2_queryctrl objects before passing them to the driver. Required a
minor change to the VIDIOC_QUERYCTRL handlers in the sample
drivers.</para>
      <para>1999-03-31: Better compatibility for v4l memory capture
ioctls. Requires changes to drivers to fully support new compatibility
features, see Driver Writer's Guide and v4l2cap.c. Added new control
IDs: V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P,
and _YUV411P to _YUV411P.</para>
      <para>1999-04-04: Added a few more control IDs.</para>
      <para>1999-04-07: Added the button control type.</para>
      <para>1999-05-02: Fixed a typo in videodev.h, and added the
V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.</para>
      <para>1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing
a malfunction of this ioctl.</para>
      <para>1999-06-05: Changed the value of
V4L2_CID_WHITENESS.</para>
    </section>

    <section>
      <title>V4L2 Version 0.20 (1999-09-10)</title>

      <para>Version 0.20 introduced a number of changes which were
<emphasis>not backward compatible</emphasis> with 0.19 and earlier
versions. Purpose of these changes was to simplify the API, while
making it more extensible and following common Linux driver API
conventions.</para>

      <orderedlist>
	<listitem>
	  <para>Some typos in <constant>V4L2_FMT_FLAG</constant>
symbols were fixed. &v4l2-clip; was changed for compatibility with
v4l. (1999-08-30)</para>
	</listitem>

	<listitem>
	  <para><constant>V4L2_TUNER_SUB_LANG1</constant> was added.
(1999-09-05)</para>
	</listitem>

	<listitem>
	  <para>All ioctl() commands that used an integer argument now
take a pointer to an integer. Where it makes sense, ioctls will return
the actual new value in the integer pointed to by the argument, a
common convention in the V4L2 API. The affected ioctls are:
VIDIOC_PREVIEW, VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
<programlisting>
err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
</programlisting> becomes <programlisting>
int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &amp;a);
</programlisting>
	  </para>
	</listitem>

	<listitem>
	  <para>All the different get- and set-format commands were
swept into one &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctl taking a union
and a type field selecting the union member as parameter. Purpose is to
simplify the API by eliminating several ioctls and to allow new and
driver private data streams without adding new ioctls.</para>

	  <para>This change obsoletes the following ioctls:
<constant>VIDIOC_S_INFMT</constant>,
<constant>VIDIOC_G_INFMT</constant>,
<constant>VIDIOC_S_OUTFMT</constant>,
<constant>VIDIOC_G_OUTFMT</constant>,
<constant>VIDIOC_S_VBIFMT</constant> and
<constant>VIDIOC_G_VBIFMT</constant>. The image format structure
<structname>v4l2_format</structname> was renamed to &v4l2-pix-format;,
while &v4l2-format; is now the envelopping structure for all format
negotiations.</para>
	</listitem>

	<listitem>
	  <para>Similar to the changes above, the
<constant>VIDIOC_G_PARM</constant> and
<constant>VIDIOC_S_PARM</constant> ioctls were merged with
<constant>VIDIOC_G_OUTPARM</constant> and
<constant>VIDIOC_S_OUTPARM</constant>. A
<structfield>type</structfield> field in the new &v4l2-streamparm;
selects the respective union member.</para>

	  <para>This change obsoletes the
<constant>VIDIOC_G_OUTPARM</constant> and
<constant>VIDIOC_S_OUTPARM</constant> ioctls.</para>
	</listitem>

	<listitem>
	  <para>Control enumeration was simplified, and two new
control flags were introduced and one dropped. The
<structfield>catname</structfield> field was replaced by a
<structfield>group</structfield> field.</para>

	  <para>Drivers can now flag unsupported and temporarily
unavailable controls with <constant>V4L2_CTRL_FLAG_DISABLED</constant>
and <constant>V4L2_CTRL_FLAG_GRABBED</constant> respectively. The
<structfield>group</structfield> name indicates a possibly narrower
classification than the <structfield>category</structfield>. In other
words, there may be multiple groups within a category. Controls within
a group would typically be drawn within a group box. Controls in
different categories might have a greater separation, or may even
appear in separate windows.</para>
	</listitem>

	<listitem>
	  <para>The &v4l2-buffer; <structfield>timestamp</structfield>
was changed to a 64 bit integer, containing the sampling or output
time of the frame in nanoseconds. Additionally timestamps will be in
absolute system time, not starting from zero at the beginning of a
stream. The data type name for timestamps is stamp_t, defined as a
signed 64-bit integer. Output devices should not send a buffer out
until the time in the timestamp field has arrived. I would like to
follow SGI's lead, and adopt a multimedia timestamping system like
their UST (Unadjusted System Time). See
1084
http://web.archive.org/web/*/http://reality.sgi.com
1085
/cpirazzi_engr/lg/time/intro.html.
1086
UST uses timestamps that are 64-bit signed integers
1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478
(not struct timeval's) and given in nanosecond units. The UST clock
starts at zero when the system is booted and runs continuously and
uniformly. It takes a little over 292 years for UST to overflow. There
is no way to set the UST clock. The regular Linux time-of-day clock
can be changed periodically, which would cause errors if it were being
used for timestamping a multimedia stream. A real UST style clock will
require some support in the kernel that is not there yet. But in
anticipation, I will change the timestamp field to a 64-bit integer,
and I will change the v4l2_masterclock_gettime() function (used only
by drivers) to return a 64-bit integer.</para>
	</listitem>

	<listitem>
	  <para>A <structfield>sequence</structfield> field was added
to &v4l2-buffer;. The <structfield>sequence</structfield> field counts
captured frames, it is ignored by output devices. When a capture
driver drops a frame, the sequence number of that frame is
skipped.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 Version 0.20 incremental changes</title>
      <!-- Version number didn't change anymore, reason unknown. -->

      <para>1999-12-23: In &v4l2-vbi-format; the
<structfield>reserved1</structfield> field became
<structfield>offset</structfield>. Previously drivers were required to
clear the <structfield>reserved1</structfield> field.</para>

      <para>2000-01-13: The
      <constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant> flag was added.</para>

      <para>2000-07-31: The <filename>linux/poll.h</filename> header
is now included by <filename>videodev.h</filename> for compatibility
with the original <filename>videodev.h</filename> file.</para>

      <para>2000-11-20: <constant>V4L2_TYPE_VBI_OUTPUT</constant> and
<constant>V4L2_PIX_FMT_Y41P</constant> were added.</para>

      <para>2000-11-25: <constant>V4L2_TYPE_VBI_INPUT</constant> was
added.</para>

      <para>2000-12-04: A couple typos in symbol names were fixed.</para>

      <para>2001-01-18: To avoid namespace conflicts the
<constant>fourcc</constant> macro defined in the
<filename>videodev.h</filename> header file was renamed to
<constant>v4l2_fourcc</constant>.</para>

      <para>2001-01-25: A possible driver-level compatibility problem
between the <filename>videodev.h</filename> file in Linux 2.4.0 and
the <filename>videodev.h</filename> file included in the
<filename>videodevX</filename> patch was fixed. Users of an earlier
version of <filename>videodevX</filename> on Linux 2.4.0 should
recompile their V4L and V4L2 drivers.</para>

      <para>2001-01-26: A possible kernel-level incompatibility
between the <filename>videodev.h</filename> file in the
<filename>videodevX</filename> patch and the
<filename>videodev.h</filename> file in Linux 2.2.x with devfs patches
applied was fixed.</para>

      <para>2001-03-02: Certain V4L ioctls which pass data in both
direction although they are defined with read-only parameter, did not
work correctly through the backward compatibility layer.
[Solution?]</para>

      <para>2001-04-13: Big endian 16-bit RGB formats were added.</para>

      <para>2001-09-17: New YUV formats and the &VIDIOC-G-FREQUENCY; and
&VIDIOC-S-FREQUENCY; ioctls were added. (The old
<constant>VIDIOC_G_FREQ</constant> and
<constant>VIDIOC_S_FREQ</constant> ioctls did not take multiple tuners
into account.)</para>

      <para>2000-09-18: <constant>V4L2_BUF_TYPE_VBI</constant> was
added. This may <emphasis>break compatibility</emphasis> as the
&VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls may fail now if the struct
<structname>v4l2_fmt</structname> <structfield>type</structfield>
field does not contain <constant>V4L2_BUF_TYPE_VBI</constant>. In the
documentation of the &v4l2-vbi-format;
<structfield>offset</structfield> field the ambiguous phrase "rising
edge" was changed to "leading edge".</para>
    </section>

    <section>
      <title>V4L2 Version 0.20 2000-11-23</title>

      <para>A number of changes were made to the raw VBI
interface.</para>

      <orderedlist>
	<listitem>
	  <para>Figures clarifying the line numbering scheme were
added to the V4L2 API specification. The
<structfield>start</structfield>[0] and
<structfield>start</structfield>[1] fields no longer count line
numbers beginning at zero. Rationale: a) The previous definition was
unclear. b) The <structfield>start</structfield>[] values are ordinal
numbers. c) There is no point in inventing a new line numbering
scheme. We now use line number as defined by ITU-R, period.
Compatibility: Add one to the start values. Applications depending on
the previous semantics may not function correctly.</para>
	</listitem>

	<listitem>
	  <para>The restriction "count[0] &gt; 0 and count[1] &gt; 0"
has been relaxed  to "(count[0] + count[1]) &gt; 0". Rationale:
Drivers may allocate resources at scan line granularity and some data
services are transmitted only on the first field. The comment that
both <structfield>count</structfield> values will usually be equal is
misleading and pointless and has been removed. This change
<emphasis>breaks compatibility</emphasis> with earlier versions:
Drivers may return EINVAL, applications may not function
correctly.</para>
	</listitem>

	<listitem>
	  <para>Drivers are again permitted to return negative
(unknown) start values as proposed earlier. Why this feature was
dropped is unclear. This change may <emphasis>break
compatibility</emphasis> with applications depending on the start
values being positive. The use of <constant>EBUSY</constant> and
<constant>EINVAL</constant> error codes with the &VIDIOC-S-FMT; ioctl
was clarified. The &EBUSY; was finally documented, and the
<structfield>reserved2</structfield> field which was previously
mentioned only in the <filename>videodev.h</filename> header
file.</para>
	</listitem>

	<listitem>
	  <para>New buffer types
<constant>V4L2_TYPE_VBI_INPUT</constant> and
<constant>V4L2_TYPE_VBI_OUTPUT</constant> were added. The former is an
alias for the old <constant>V4L2_TYPE_VBI</constant>, the latter was
missing in the <filename>videodev.h</filename> file.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 Version 0.20 2002-07-25</title>
      <para>Added sliced VBI interface proposal.</para>
    </section>

    <section>
      <title>V4L2 in Linux 2.5.46, 2002-10</title>

      <para>Around October-November 2002, prior to an announced
feature freeze of Linux 2.5, the API was revised, drawing from
experience with V4L2 0.20. This unnamed version was finally merged
into Linux 2.5.46.</para>

      <orderedlist>
	<listitem>
	  <para>As specified in <xref linkend="related" />, drivers
must make related device functions available under all minor device
numbers.</para>
	</listitem>

	<listitem>
	  <para>The &func-open; function requires access mode
<constant>O_RDWR</constant> regardless of the device type. All V4L2
drivers exchanging data with applications must support the
<constant>O_NONBLOCK</constant> flag. The <constant>O_NOIO</constant>
flag, a V4L2 symbol which aliased the meaningless
<constant>O_TRUNC</constant> to indicate accesses without data
exchange (panel applications) was dropped. Drivers must stay in "panel
mode" until the application attempts to initiate a data exchange, see
<xref linkend="open" />.</para>
	</listitem>

	<listitem>
	  <para>The &v4l2-capability; changed dramatically. Note that
also the size of the structure changed, which is encoded in the ioctl
request code, thus older V4L2 devices will respond with an &EINVAL; to
the new &VIDIOC-QUERYCAP; ioctl.</para>

	  <para>There are new fields to identify the driver, a new RDS
device function <constant>V4L2_CAP_RDS_CAPTURE</constant>, the
<constant>V4L2_CAP_AUDIO</constant> flag indicates if the device has
any audio connectors, another I/O capability
<constant>V4L2_CAP_ASYNCIO</constant> can be flagged. In response to
these changes the <structfield>type</structfield> field became a bit
set and was merged into the <structfield>flags</structfield> field.
<constant>V4L2_FLAG_TUNER</constant> was renamed to
<constant>V4L2_CAP_TUNER</constant>,
<constant>V4L2_CAP_VIDEO_OVERLAY</constant> replaced
<constant>V4L2_FLAG_PREVIEW</constant> and
<constant>V4L2_CAP_VBI_CAPTURE</constant> and
<constant>V4L2_CAP_VBI_OUTPUT</constant> replaced
<constant>V4L2_FLAG_DATA_SERVICE</constant>.
<constant>V4L2_FLAG_READ</constant> and
<constant>V4L2_FLAG_WRITE</constant> were merged into
<constant>V4L2_CAP_READWRITE</constant>.</para>

	  <para>The redundant fields
<structfield>inputs</structfield>, <structfield>outputs</structfield>
and <structfield>audios</structfield> were removed. These properties
can be determined as described in <xref linkend="video" /> and <xref
linkend="audio" />.</para>

	  <para>The somewhat volatile and therefore barely useful
fields <structfield>maxwidth</structfield>,
<structfield>maxheight</structfield>,
<structfield>minwidth</structfield>,
<structfield>minheight</structfield>,
<structfield>maxframerate</structfield> were removed. This information
is available as described in <xref linkend="format" /> and
<xref linkend="standard" />.</para>

	  <para><constant>V4L2_FLAG_SELECT</constant> was removed. We
believe the select() function is important enough to require support
of it in all V4L2 drivers exchanging data with applications. The
redundant <constant>V4L2_FLAG_MONOCHROME</constant> flag was removed,
this information is available as described in <xref
	      linkend="format" />.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-input; the
<structfield>assoc_audio</structfield> field and the
<structfield>capability</structfield> field and its only flag
<constant>V4L2_INPUT_CAP_AUDIO</constant> was replaced by the new
<structfield>audioset</structfield> field. Instead of linking one
video input to one audio input this field reports all audio inputs
this video input combines with.</para>

	  <para>New fields are <structfield>tuner</structfield>
(reversing the former link from tuners to video inputs),
<structfield>std</structfield> and
<structfield>status</structfield>.</para>

	  <para>Accordingly &v4l2-output; lost its
<structfield>capability</structfield> and
<structfield>assoc_audio</structfield> fields.
<structfield>audioset</structfield>,
<structfield>modulator</structfield> and
<structfield>std</structfield> where added instead.</para>
	</listitem>

	<listitem>
	  <para>The &v4l2-audio; field
<structfield>audio</structfield> was renamed to
<structfield>index</structfield>, for consistency with other
structures. A new capability flag
<constant>V4L2_AUDCAP_STEREO</constant> was added to indicated if the
audio input in question supports stereo sound.
<constant>V4L2_AUDCAP_EFFECTS</constant> and the corresponding
<constant>V4L2_AUDMODE</constant> flags where removed. This can be
easily implemented using controls. (However the same applies to AVL
which is still there.)</para>

	  <para>Again for consistency the &v4l2-audioout; field
<structfield>audio</structfield> was renamed to
<structfield>index</structfield>.</para>
	</listitem>

	<listitem>
	  <para>The &v4l2-tuner;
<structfield>input</structfield> field was replaced by an
<structfield>index</structfield> field, permitting devices with
multiple tuners. The link between video inputs and tuners is now
reversed, inputs point to their tuner. The
<structfield>std</structfield> substructure became a
simple set (more about this below) and moved into &v4l2-input;. A
<structfield>type</structfield> field was added.</para>

	  <para>Accordingly in &v4l2-modulator; the
<structfield>output</structfield> was replaced by an
<structfield>index</structfield> field.</para>

	  <para>In &v4l2-frequency; the
<structfield>port</structfield> field was replaced by a
<structfield>tuner</structfield> field containing the respective tuner
or modulator index number. A tuner <structfield>type</structfield>
field was added and the <structfield>reserved</structfield> field
became larger for future extensions (satellite tuners in
particular).</para>
	</listitem>

	<listitem>
	  <para>The idea of completely transparent video standards was
dropped. Experience showed that applications must be able to work with
video standards beyond presenting the user a menu. Instead of
enumerating supported standards with an ioctl applications can now
refer to standards by &v4l2-std-id; and symbols defined in the
<filename>videodev2.h</filename> header file. For details see <xref
	      linkend="standard" />. The &VIDIOC-G-STD; and
&VIDIOC-S-STD; now take a pointer to this type as argument.
&VIDIOC-QUERYSTD; was added to autodetect the received standard, if
the hardware has this capability. In &v4l2-standard; an
<structfield>index</structfield> field was added for &VIDIOC-ENUMSTD;.
A &v4l2-std-id; field named <structfield>id</structfield> was added as
machine readable identifier, also replacing the
<structfield>transmission</structfield> field. The misleading
<structfield>framerate</structfield> field was renamed
to <structfield>frameperiod</structfield>. The now obsolete
<structfield>colorstandard</structfield> information, originally
needed to distguish between variations of standards, were
removed.</para>

	  <para>Struct <structname>v4l2_enumstd</structname> ceased to
be. &VIDIOC-ENUMSTD; now takes a pointer to a &v4l2-standard;
directly. The information which standards are supported by a
particular video input or output moved into &v4l2-input; and
&v4l2-output; fields named <structfield>std</structfield>,
respectively.</para>
	</listitem>

	<listitem>
	  <para>The &v4l2-queryctrl; fields
<structfield>category</structfield> and
<structfield>group</structfield> did not catch on and/or were not
implemented as expected and therefore removed.</para>
	</listitem>

	<listitem>
	  <para>The &VIDIOC-TRY-FMT; ioctl was added to negotiate data
formats as with &VIDIOC-S-FMT;, but without the overhead of
programming the hardware and regardless of I/O in progress.</para>

	  <para>In &v4l2-format; the <structfield>fmt</structfield>
union was extended to contain &v4l2-window;. All image format
negotiations are now possible with <constant>VIDIOC_G_FMT</constant>,
<constant>VIDIOC_S_FMT</constant> and
<constant>VIDIOC_TRY_FMT</constant>; ioctl. The
<constant>VIDIOC_G_WIN</constant> and
<constant>VIDIOC_S_WIN</constant> ioctls to prepare for a video
overlay were removed. The <structfield>type</structfield> field
changed to type &v4l2-buf-type; and the buffer type names changed as
follows.<informaltable>
	      <tgroup cols="2">
		<thead>
		  <row>
		    <entry>Old defines</entry>
		    <entry>&v4l2-buf-type;</entry>
		  </row>
		</thead>
		<tbody valign="top">
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_CAPTURE</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant></entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_CODECIN</constant></entry>
		    <entry>Omitted for now</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_CODECOUT</constant></entry>
		    <entry>Omitted for now</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_EFFECTSIN</constant></entry>
		    <entry>Omitted for now</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_EFFECTSIN2</constant></entry>
		    <entry>Omitted for now</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_EFFECTSOUT</constant></entry>
		    <entry>Omitted for now</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_VIDEOOUT</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_VBI_CAPTURE</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant></entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_BUF_TYPE_PRIVATE_BASE</constant></entry>
1479
		    <entry><constant>V4L2_BUF_TYPE_PRIVATE</constant> (but this is deprecated)</entry>
1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706
		  </row>
		</tbody>
	      </tgroup>
	    </informaltable></para>
	</listitem>

	<listitem>
	  <para>In &v4l2-fmtdesc; a &v4l2-buf-type; field named
<structfield>type</structfield> was added as in &v4l2-format;. The
<constant>VIDIOC_ENUM_FBUFFMT</constant> ioctl is no longer needed and
was removed. These calls can be replaced by &VIDIOC-ENUM-FMT; with
type <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-pix-format; the
<structfield>depth</structfield> field was removed, assuming
applications which recognize the format by its four-character-code
already know the color depth, and others do not care about it. The
same rationale lead to the removal of the
<constant>V4L2_FMT_FLAG_COMPRESSED</constant> flag. The
<constant>V4L2_FMT_FLAG_SWCONVECOMPRESSED</constant> flag was removed
because drivers are not supposed to convert images in kernel space. A
user library of conversion functions should be provided instead. The
<constant>V4L2_FMT_FLAG_BYTESPERLINE</constant> flag was redundant.
Applications can set the <structfield>bytesperline</structfield> field
to zero to get a reasonable default. Since the remaining flags were
replaced as well, the <structfield>flags</structfield> field itself
was removed.</para>
	  <para>The interlace flags were replaced by a &v4l2-field;
value in a newly added <structfield>field</structfield>
field.<informaltable>
	      <tgroup cols="2">
		<thead>
		  <row>
		    <entry>Old flag</entry>
		    <entry>&v4l2-field;</entry>
		  </row>
		</thead>
		<tbody valign="top">
		  <row>
		    <entry><constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant></entry>
		    <entry>?</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_FMT_FLAG_INTERLACED</constant>
= <constant>V4L2_FMT_FLAG_COMBINED</constant></entry>
		    <entry><constant>V4L2_FIELD_INTERLACED</constant></entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_FMT_FLAG_TOPFIELD</constant>
= <constant>V4L2_FMT_FLAG_ODDFIELD</constant></entry>
		    <entry><constant>V4L2_FIELD_TOP</constant></entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_FMT_FLAG_BOTFIELD</constant>
= <constant>V4L2_FMT_FLAG_EVENFIELD</constant></entry>
		    <entry><constant>V4L2_FIELD_BOTTOM</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_FIELD_SEQ_TB</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_FIELD_SEQ_BT</constant></entry>
		  </row>
		  <row>
		    <entry><constant>-</constant></entry>
		    <entry><constant>V4L2_FIELD_ALTERNATE</constant></entry>
		  </row>
		</tbody>
	      </tgroup>
	    </informaltable></para>

	  <para>The color space flags were replaced by a
&v4l2-colorspace; value in a newly added
<structfield>colorspace</structfield> field, where one of
<constant>V4L2_COLORSPACE_SMPTE170M</constant>,
<constant>V4L2_COLORSPACE_BT878</constant>,
<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant> or
<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant> replaces
<constant>V4L2_FMT_CS_601YUV</constant>.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-requestbuffers; the
<structfield>type</structfield> field was properly defined as
&v4l2-buf-type;. Buffer types changed as mentioned above. A new
<structfield>memory</structfield> field of type &v4l2-memory; was
added to distinguish between I/O methods using buffers allocated
by the driver or the application. See <xref linkend="io" /> for
details.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-buffer; the <structfield>type</structfield>
field was properly defined as &v4l2-buf-type;. Buffer types changed as
mentioned above. A <structfield>field</structfield> field of type
&v4l2-field; was added to indicate if a buffer contains a top or
bottom field. The old field flags were removed. Since no unadjusted
system time clock was added to the kernel as planned, the
<structfield>timestamp</structfield> field changed back from type
stamp_t, an unsigned 64 bit integer expressing the sample time in
nanoseconds, to struct <structname>timeval</structname>. With the
addition of a second memory mapping method the
<structfield>offset</structfield> field moved into union
<structfield>m</structfield>, and a new
<structfield>memory</structfield> field of type &v4l2-memory; was
added to distinguish between I/O methods. See <xref linkend="io" />
for details.</para>

	  <para>The <constant>V4L2_BUF_REQ_CONTIG</constant>
flag was used by the V4L compatibility layer, after changes to this
code it was no longer needed. The
<constant>V4L2_BUF_ATTR_DEVICEMEM</constant> flag would indicate if
the buffer was indeed allocated in device memory rather than DMA-able
system memory. It was barely useful and so was removed.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-framebuffer; the
<structfield>base[3]</structfield> array anticipating double- and
triple-buffering in off-screen video memory, however without defining
a synchronization mechanism, was replaced by a single pointer. The
<constant>V4L2_FBUF_CAP_SCALEUP</constant> and
<constant>V4L2_FBUF_CAP_SCALEDOWN</constant> flags were removed.
Applications can determine this capability more accurately using the
new cropping and scaling interface. The
<constant>V4L2_FBUF_CAP_CLIPPING</constant> flag was replaced by
<constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> and
<constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant>.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-clip; the <structfield>x</structfield>,
<structfield>y</structfield>, <structfield>width</structfield> and
<structfield>height</structfield> field moved into a
<structfield>c</structfield> substructure of type &v4l2-rect;. The
<structfield>x</structfield> and <structfield>y</structfield> fields
were renamed to <structfield>left</structfield> and
<structfield>top</structfield>, &ie; offsets to a context dependent
origin.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-window; the <structfield>x</structfield>,
<structfield>y</structfield>, <structfield>width</structfield> and
<structfield>height</structfield> field moved into a
<structfield>w</structfield> substructure as above. A
<structfield>field</structfield> field of type %v4l2-field; was added
to distinguish between field and frame (interlaced) overlay.</para>
	</listitem>

	<listitem>
	  <para>The digital zoom interface, including struct
<structname>v4l2_zoomcap</structname>, struct
<structname>v4l2_zoom</structname>,
<constant>V4L2_ZOOM_NONCAP</constant> and
<constant>V4L2_ZOOM_WHILESTREAMING</constant> was replaced by a new
cropping and scaling interface. The previously unused struct
<structname>v4l2_cropcap</structname> and
<structname>v4l2_crop</structname> where redefined for this purpose.
See <xref linkend="crop" /> for details.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-vbi-format; the
<structfield>SAMPLE_FORMAT</structfield> field now contains a
four-character-code as used to identify video image formats and
<constant>V4L2_PIX_FMT_GREY</constant> replaces the
<constant>V4L2_VBI_SF_UBYTE</constant> define. The
<structfield>reserved</structfield> field was extended.</para>
	</listitem>

	<listitem>
	  <para>In &v4l2-captureparm; the type of the
<structfield>timeperframe</structfield> field changed from unsigned
long to &v4l2-fract;. This allows the accurate expression of multiples
of the NTSC-M frame rate 30000 / 1001. A new field
<structfield>readbuffers</structfield> was added to control the driver
behaviour in read I/O mode.</para>

	  <para>Similar changes were made to &v4l2-outputparm;.</para>
	</listitem>

	<listitem>
	  <para>The struct <structname>v4l2_performance</structname>
and <constant>VIDIOC_G_PERF</constant> ioctl were dropped. Except when
using the <link linkend="rw">read/write I/O method</link>, which is
limited anyway, this information is already available to
applications.</para>
	</listitem>

	<listitem>
	  <para>The example transformation from RGB to YCbCr color
space in the old V4L2 documentation was inaccurate, this has been
corrected in <xref linkend="pixfmt" />.<!-- 0.5670G should be
0.587, and 127/112 != 255/224 --></para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 2003-06-19</title>

      <orderedlist>
	<listitem>
	  <para>A new capability flag
<constant>V4L2_CAP_RADIO</constant> was added for radio devices. Prior
to this change radio devices would identify solely by having exactly one
tuner whose type field reads <constant>V4L2_TUNER_RADIO</constant>.</para>
	</listitem>

	<listitem>
	  <para>An optional driver access priority mechanism was
added, see <xref linkend="app-pri" /> for details.</para>
	</listitem>

	<listitem>
	  <para>The audio input and output interface was found to be
incomplete.</para>
	  <para>Previously the &VIDIOC-G-AUDIO;
ioctl would enumerate the available audio inputs. An ioctl to
determine the current audio input, if more than one combines with the
current video input, did not exist. So
<constant>VIDIOC_G_AUDIO</constant> was renamed to
1707 1708
<constant>VIDIOC_G_AUDIO_OLD</constant>, this ioctl was removed on
Kernel 2.6.39. The &VIDIOC-ENUMAUDIO; ioctl was added to enumerate
1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721
audio inputs, while &VIDIOC-G-AUDIO; now reports the current audio
input.</para>
	  <para>The same changes were made to &VIDIOC-G-AUDOUT; and
&VIDIOC-ENUMAUDOUT;.</para>
	  <para>Until further the "videodev" module will automatically
translate between the old and new ioctls, but drivers and applications
must be updated to successfully compile again.</para>
	</listitem>

	<listitem>
	  <para>The &VIDIOC-OVERLAY; ioctl was incorrectly defined with
write-read parameter. It was changed to write-only, while the write-read
version was renamed to <constant>VIDIOC_OVERLAY_OLD</constant>. The old
1722
ioctl was removed on Kernel 2.6.39. Until further the "videodev"
1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739
kernel module will automatically translate to the new version, so drivers
must be recompiled, but not applications.</para>
	</listitem>

	<listitem>
	  <para><xref linkend="overlay" /> incorrectly stated that
clipping rectangles define regions where the video can be seen.
Correct is that clipping rectangles define regions where
<emphasis>no</emphasis> video shall be displayed and so the graphics
surface can be seen.</para>
	</listitem>

	<listitem>
	  <para>The &VIDIOC-S-PARM; and &VIDIOC-S-CTRL; ioctls were
defined with write-only parameter, inconsistent with other ioctls
modifying their argument. They were changed to write-read, while a
<constant>_OLD</constant> suffix was added to the write-only versions.
1740
The old ioctls were removed on Kernel 2.6.39. Drivers and
1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810
applications assuming a constant parameter need an update.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 2003-11-05</title>
      <orderedlist>
	<listitem>
	  <para>In <xref linkend="pixfmt-rgb" /> the following pixel
formats were incorrectly transferred from Bill Dirks' V4L2
specification. Descriptions below refer to bytes in memory, in
ascending address order.<informaltable>
	      <tgroup cols="3">
		<thead>
		  <row>
		    <entry>Symbol</entry>
		    <entry>In this document prior to revision
0.5</entry>
		    <entry>Corrected</entry>
		  </row>
		</thead>
		<tbody valign="top">
		  <row>
		    <entry><constant>V4L2_PIX_FMT_RGB24</constant></entry>
		    <entry>B, G, R</entry>
		    <entry>R, G, B</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_PIX_FMT_BGR24</constant></entry>
		    <entry>R, G, B</entry>
		    <entry>B, G, R</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_PIX_FMT_RGB32</constant></entry>
		    <entry>B, G, R, X</entry>
		    <entry>R, G, B, X</entry>
		  </row>
		  <row>
		    <entry><constant>V4L2_PIX_FMT_BGR32</constant></entry>
		    <entry>R, G, B, X</entry>
		    <entry>B, G, R, X</entry>
		  </row>
		</tbody>
	      </tgroup>
	    </informaltable> The
<constant>V4L2_PIX_FMT_BGR24</constant> example was always
correct.</para>
	  <para>In <xref linkend="v4l-image-properties" /> the mapping
of the V4L <constant>VIDEO_PALETTE_RGB24</constant> and
<constant>VIDEO_PALETTE_RGB32</constant> formats to V4L2 pixel formats
was accordingly corrected.</para>
	</listitem>

	<listitem>
	  <para>Unrelated to the fixes above, drivers may still
interpret some V4L2 RGB pixel formats differently. These issues have
yet to be addressed, for details see <xref
	      linkend="pixfmt-rgb" />.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.6, 2004-05-09</title>
      <orderedlist>
	<listitem>
	  <para>The &VIDIOC-CROPCAP; ioctl was incorrectly defined
with read-only parameter. It is now defined as write-read ioctl, while
the read-only version was renamed to
1811 1812
<constant>VIDIOC_CROPCAP_OLD</constant>. The old ioctl was removed
on Kernel 2.6.39.</para>
1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.8</title>
      <orderedlist>
	<listitem>
	  <para>A new field <structfield>input</structfield> (former
<structfield>reserved[0]</structfield>) was added to the &v4l2-buffer;
structure. Purpose of this field is to alternate between video inputs
(&eg; cameras) in step with the video capturing process. This function
must be enabled with the new <constant>V4L2_BUF_FLAG_INPUT</constant>
flag. The <structfield>flags</structfield> field is no longer
read-only.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2004-08-01</title>

      <orderedlist>
	<listitem>
	  <para>The return value of the
<xref linkend="func-open" /> function was incorrectly documented.</para>
	</listitem>

	<listitem>
	  <para>Audio output ioctls end in -AUDOUT, not -AUDIOOUT.</para>
	</listitem>

	<listitem>
	  <para>In the Current Audio Input example the
<constant>VIDIOC_G_AUDIO</constant> ioctl took the wrong
argument.</para>
	</listitem>

	<listitem>
	  <para>The documentation of the &VIDIOC-QBUF; and
&VIDIOC-DQBUF; ioctls did not mention the &v4l2-buffer;
<structfield>memory</structfield> field. It was also missing from
examples. Also on the <constant>VIDIOC_DQBUF</constant> page the &EIO;
was not documented.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.14</title>
      <orderedlist>
	<listitem>
	  <para>A new sliced VBI interface was added. It is documented
in <xref linkend="sliced" /> and replaces the interface first
proposed in V4L2 specification 0.8.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.15</title>
      <orderedlist>
	<listitem>
	  <para>The &VIDIOC-LOG-STATUS; ioctl was added.</para>
	</listitem>

	<listitem>
	  <para>New video standards
<constant>V4L2_STD_NTSC_443</constant>,
<constant>V4L2_STD_SECAM_LC</constant>,
<constant>V4L2_STD_SECAM_DK</constant> (a set of SECAM D, K and K1),
and <constant>V4L2_STD_ATSC</constant> (a set of
<constant>V4L2_STD_ATSC_8_VSB</constant> and
<constant>V4L2_STD_ATSC_16_VSB</constant>) were defined. Note the
<constant>V4L2_STD_525_60</constant> set now includes
<constant>V4L2_STD_NTSC_443</constant>. See also <xref
	      linkend="v4l2-std-id" />.</para>
	</listitem>

	<listitem>
	  <para>The <constant>VIDIOC_G_COMP</constant> and
<constant>VIDIOC_S_COMP</constant> ioctl were renamed to
<constant>VIDIOC_G_MPEGCOMP</constant> and
<constant>VIDIOC_S_MPEGCOMP</constant> respectively. Their argument
was replaced by a struct
<structname>v4l2_mpeg_compression</structname> pointer. (The
<constant>VIDIOC_G_MPEGCOMP</constant> and
<constant>VIDIOC_S_MPEGCOMP</constant> ioctls where removed in Linux
2.6.25.)</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2005-11-27</title>
      <para>The capture example in <xref linkend="capture-example" />
called the &VIDIOC-S-CROP; ioctl without checking if cropping is
supported. In the video standard selection example in
<xref linkend="standard" /> the &VIDIOC-S-STD; call used the wrong
argument type.</para>
    </section>

    <section>
      <title>V4L2 spec erratum 2006-01-10</title>
      <orderedlist>
	<listitem>
	  <para>The <constant>V4L2_IN_ST_COLOR_KILL</constant> flag in
&v4l2-input; not only indicates if the color killer is enabled, but
also if it is active. (The color killer disables color decoding when
it detects no color in the video signal to improve the image
quality.)</para>
	</listitem>

	<listitem>
	  <para>&VIDIOC-S-PARM; is a write-read ioctl, not write-only as
stated on its reference page. The ioctl changed in 2003 as noted above.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2006-02-03</title>
      <orderedlist>
	<listitem>
	  <para>In &v4l2-captureparm; and &v4l2-outputparm; the
<structfield>timeperframe</structfield> field gives the time in
seconds, not microseconds.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2006-02-04</title>
      <orderedlist>
	<listitem>
	  <para>The <structfield>clips</structfield> field in
&v4l2-window; must point to an array of &v4l2-clip;, not a linked
list, because drivers ignore the struct
<structname>v4l2_clip</structname>.<structfield>next</structfield>
pointer.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.17</title>
      <orderedlist>
	<listitem>
	  <para>New video standard macros were added:
<constant>V4L2_STD_NTSC_M_KR</constant> (NTSC M South Korea), and the
sets <constant>V4L2_STD_MN</constant>,
<constant>V4L2_STD_B</constant>, <constant>V4L2_STD_GH</constant> and
<constant>V4L2_STD_DK</constant>. The
<constant>V4L2_STD_NTSC</constant> and
<constant>V4L2_STD_SECAM</constant> sets now include
<constant>V4L2_STD_NTSC_M_KR</constant> and
<constant>V4L2_STD_SECAM_LC</constant> respectively.</para>
	</listitem>

	<listitem>
	  <para>A new <constant>V4L2_TUNER_MODE_LANG1_LANG2</constant>
was defined to record both languages of a bilingual program. The
use of <constant>V4L2_TUNER_MODE_STEREO</constant> for this purpose
is deprecated now. See the &VIDIOC-G-TUNER; section for
details.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2006-09-23 (Draft 0.15)</title>
      <orderedlist>
	<listitem>
	  <para>In various places
<constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> and
<constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant> of the sliced VBI
interface were not mentioned along with other buffer types.</para>
	</listitem>

	<listitem>
	  <para>In <xref linkend="vidioc-g-audio" /> it was clarified
that the &v4l2-audio; <structfield>mode</structfield> field is a flags
field.</para>
	</listitem>

	<listitem>
	  <para><xref linkend="vidioc-querycap" /> did not mention the
sliced VBI and radio capability flags.</para>
	</listitem>

	<listitem>
	  <para>In <xref linkend="vidioc-g-frequency" /> it was
clarified that applications must initialize the tuner
<structfield>type</structfield> field of &v4l2-frequency; before
calling &VIDIOC-S-FREQUENCY;.</para>
	</listitem>

	<listitem>
	  <para>The <structfield>reserved</structfield> array
in &v4l2-requestbuffers; has 2 elements, not 32.</para>
	</listitem>

	<listitem>
	  <para>In <xref linkend="output" /> and <xref
	      linkend="raw-vbi" /> the device file names
<filename>/dev/vout</filename> which never caught on were replaced
by <filename>/dev/video</filename>.</para>
	</listitem>

	<listitem>
	  <para>With Linux 2.6.15 the possible range for VBI device minor
numbers was extended from 224-239 to 224-255. Accordingly device file names
<filename>/dev/vbi0</filename> to <filename>/dev/vbi31</filename> are
possible now.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.18</title>
      <orderedlist>
	<listitem>
	  <para>New ioctls &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS;
and &VIDIOC-TRY-EXT-CTRLS; were added, a flag to skip unsupported
controls with &VIDIOC-QUERYCTRL;, new control types
<constant>V4L2_CTRL_TYPE_INTEGER64</constant> and
<constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant> (<xref
	      linkend="v4l2-ctrl-type" />), and new control flags
<constant>V4L2_CTRL_FLAG_READ_ONLY</constant>,
<constant>V4L2_CTRL_FLAG_UPDATE</constant>,
<constant>V4L2_CTRL_FLAG_INACTIVE</constant> and
<constant>V4L2_CTRL_FLAG_SLIDER</constant> (<xref
	      linkend="control-flags" />). See <xref
	      linkend="extended-controls" /> for details.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.19</title>
      <orderedlist>
	<listitem>
	  <para>In &v4l2-sliced-vbi-cap; a buffer type field was added
replacing a reserved field. Note on architectures where the size of
enum types differs from int types the size of the structure changed.
The &VIDIOC-G-SLICED-VBI-CAP; ioctl was redefined from being read-only
to write-read. Applications must initialize the type field and clear
the reserved fields now. These changes may <emphasis>break the
compatibility</emphasis> with older drivers and applications.</para>
	</listitem>

	<listitem>
	  <para>The ioctls &VIDIOC-ENUM-FRAMESIZES; and
&VIDIOC-ENUM-FRAMEINTERVALS; were added.</para>
	</listitem>

	<listitem>
	  <para>A new pixel format <constant>V4L2_PIX_FMT_RGB444</constant> (<xref
linkend="rgb-formats" />) was added.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 spec erratum 2006-10-12 (Draft 0.17)</title>
      <orderedlist>
	<listitem>
	  <para><constant>V4L2_PIX_FMT_HM12</constant> (<xref
linkend="reserved-formats" />) is a YUV 4:2:0, not 4:2:2 format.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.21</title>
      <orderedlist>
	<listitem>
	  <para>The <filename>videodev2.h</filename> header file is
now dual licensed under GNU General Public License version two or
later, and under a 3-clause BSD-style license.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.22</title>
      <orderedlist>
	<listitem>
	  <para>Two new field orders
	  <constant>V4L2_FIELD_INTERLACED_TB</constant> and
	  <constant>V4L2_FIELD_INTERLACED_BT</constant> were
	  added. See <xref linkend="v4l2-field" /> for details.</para>
	</listitem>

	<listitem>
	  <para>Three new clipping/blending methods with a global or
straight or inverted local alpha value were added to the video overlay
interface. See the description of the &VIDIOC-G-FBUF; and
&VIDIOC-S-FBUF; ioctls for details.</para>
	  <para>A new <structfield>global_alpha</structfield> field
was added to <link
linkend="v4l2-window"><structname>v4l2_window</structname></link>,
extending the structure. This may <emphasis>break
compatibility</emphasis> with applications using a struct
<structname>v4l2_window</structname> directly. However the <link
linkend="vidioc-g-fmt">VIDIOC_G/S/TRY_FMT</link> ioctls, which take a
pointer to a <link linkend="v4l2-format">v4l2_format</link> parent
structure with padding bytes at the end, are not affected.</para>
	</listitem>

	<listitem>
	  <para>The format of the <structfield>chromakey</structfield>
field in &v4l2-window; changed from "host order RGB32" to a pixel
value in the same format as the framebuffer. This may <emphasis>break
compatibility</emphasis> with existing applications. Drivers
supporting the "host order RGB32" format are not known.</para>
	</listitem>

      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.24</title>
      <orderedlist>
	<listitem>
	  <para>The pixel formats
<constant>V4L2_PIX_FMT_PAL8</constant>,
<constant>V4L2_PIX_FMT_YUV444</constant>,
<constant>V4L2_PIX_FMT_YUV555</constant>,
<constant>V4L2_PIX_FMT_YUV565</constant> and
<constant>V4L2_PIX_FMT_YUV32</constant> were added.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.25</title>
      <orderedlist>
	<listitem>
	  <para>The pixel formats <link linkend="V4L2-PIX-FMT-Y16">
<constant>V4L2_PIX_FMT_Y16</constant></link> and <link
linkend="V4L2-PIX-FMT-SBGGR16">
<constant>V4L2_PIX_FMT_SBGGR16</constant></link> were added.</para>
	</listitem>
	<listitem>
	  <para>New <link linkend="control">controls</link>
<constant>V4L2_CID_POWER_LINE_FREQUENCY</constant>,
<constant>V4L2_CID_HUE_AUTO</constant>,
<constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant>,
<constant>V4L2_CID_SHARPNESS</constant> and
<constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant> were added. The
controls <constant>V4L2_CID_BLACK_LEVEL</constant>,
<constant>V4L2_CID_WHITENESS</constant>,
<constant>V4L2_CID_HCENTER</constant> and
<constant>V4L2_CID_VCENTER</constant> were deprecated.
</para>
	</listitem>
	<listitem>
	  <para>A <link linkend="camera-controls">Camera controls
class</link> was added, with the new controls
<constant>V4L2_CID_EXPOSURE_AUTO</constant>,
<constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>,
<constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>,
<constant>V4L2_CID_PAN_RELATIVE</constant>,
<constant>V4L2_CID_TILT_RELATIVE</constant>,
<constant>V4L2_CID_PAN_RESET</constant>,
<constant>V4L2_CID_TILT_RESET</constant>,
<constant>V4L2_CID_PAN_ABSOLUTE</constant>,
<constant>V4L2_CID_TILT_ABSOLUTE</constant>,
<constant>V4L2_CID_FOCUS_ABSOLUTE</constant>,
<constant>V4L2_CID_FOCUS_RELATIVE</constant> and
<constant>V4L2_CID_FOCUS_AUTO</constant>.</para>
	</listitem>
	<listitem>
	  <para>The <constant>VIDIOC_G_MPEGCOMP</constant> and
<constant>VIDIOC_S_MPEGCOMP</constant> ioctls, which were superseded
by the <link linkend="extended-controls">extended controls</link>
interface in Linux 2.6.18, where finally removed from the
<filename>videodev2.h</filename> header file.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.26</title>
      <orderedlist>
	<listitem>
	  <para>The pixel formats
<constant>V4L2_PIX_FMT_Y16</constant> and
<constant>V4L2_PIX_FMT_SBGGR16</constant> were added.</para>
	</listitem>
	<listitem>
	  <para>Added user controls
<constant>V4L2_CID_CHROMA_AGC</constant> and
<constant>V4L2_CID_COLOR_KILLER</constant>.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.27</title>
      <orderedlist>
	<listitem>
	  <para>The &VIDIOC-S-HW-FREQ-SEEK; ioctl and the
<constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability were added.</para>
	</listitem>
	<listitem>
	  <para>The pixel formats
<constant>V4L2_PIX_FMT_YVYU</constant>,
<constant>V4L2_PIX_FMT_PCA501</constant>,
<constant>V4L2_PIX_FMT_PCA505</constant>,
<constant>V4L2_PIX_FMT_PCA508</constant>,
<constant>V4L2_PIX_FMT_PCA561</constant>,
<constant>V4L2_PIX_FMT_SGBRG8</constant>,
<constant>V4L2_PIX_FMT_PAC207</constant> and
<constant>V4L2_PIX_FMT_PJPG</constant> were added.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.28</title>
      <orderedlist>
	<listitem>
	  <para>Added <constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant> and
<constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant> MPEG audio encodings.</para>
	</listitem>
	<listitem>
	  <para>Added <constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant> MPEG
video encoding.</para>
	</listitem>
	<listitem>
	  <para>The pixel formats
<constant>V4L2_PIX_FMT_SGRBG10</constant> and
<constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant> were added.</para>
	</listitem>
      </orderedlist>
    </section>

    <section>
      <title>V4L2 in Linux 2.6.29</title>
      <orderedlist>
	<listitem>
	  <para>The <constant>VIDIOC_G_CHIP_IDENT</constant> ioctl was renamed
2257
to <constant>VIDIOC_G_CHIP_IDENT_OLD</constant> and <constant>VIDIOC_DBG_G_CHIP_IDENT</constant>
2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284
was introduced in its place. The old struct <structname>v4l2_chip_ident</structname>
was renamed to <structname id="v4l2-chip-ident-old">v4l2_chip_ident_old</structname>.</para>
	</listitem>
	<listitem>
	  <para>The pixel formats
<constant>V4L2_PIX_FMT_VYUY</constant>,
<constant>V4L2_PIX_FMT_NV16</constant> and
<constant>V4L2_PIX_FMT_NV61</constant> were added.</para>
	</listitem>
	<listitem>
	  <para>Added camera controls
<constant>V4L2_CID_ZOOM_ABSOLUTE</constant>,
<constant>V4L2_CID_ZOOM_RELATIVE</constant>,
<constant>V4L2_CID_ZOOM_CONTINUOUS</constant> and
<constant>V4L2_CID_PRIVACY</constant>.</para>
	</listitem>
      </orderedlist>
    </section>
    <section>
      <title>V4L2 in Linux 2.6.30</title>
      <orderedlist>
	<listitem>
	  <para>New control flag <constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant> was added.</para>
	</listitem>
	<listitem>
	  <para>New control <constant>V4L2_CID_COLORFX</constant> was added.</para>
	</listitem>
2285 2286
      </orderedlist>
    </section>
2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312
    <section>
      <title>V4L2 in Linux 2.6.32</title>
      <orderedlist>
	<listitem>
	  <para>In order to be easier to compare a V4L2 API and a kernel
version, now V4L2 API is numbered using the Linux Kernel version numeration.</para>
	</listitem>
	<listitem>
	  <para>Finalized the RDS capture API. See <xref linkend="rds" /> for
more information.</para>
	</listitem>
	<listitem>
	  <para>Added new capabilities for modulators and RDS encoders.</para>
	</listitem>
	<listitem>
	  <para>Add description for libv4l API.</para>
	</listitem>
	<listitem>
	  <para>Added support for string controls via new type <constant>V4L2_CTRL_TYPE_STRING</constant>.</para>
	</listitem>
	<listitem>
	  <para>Added <constant>V4L2_CID_BAND_STOP_FILTER</constant> documentation.</para>
	</listitem>
	<listitem>
	  <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para>
	</listitem>
2313 2314 2315
<listitem>
	  <para>Added FM Receiver (FM RX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_RX</constant> and their Control IDs.</para>
	</listitem>
2316 2317 2318
	<listitem>
	  <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para>
	</listitem>
2319 2320 2321 2322 2323 2324 2325 2326 2327 2328
      </orderedlist>
    </section>
    <section>
      <title>V4L2 in Linux 2.6.33</title>
      <orderedlist>
	<listitem>
	  <para>Added support for Digital Video timings in order to support HDTV receivers and transmitters.</para>
	</listitem>
      </orderedlist>
    </section>
2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339
    <section>
      <title>V4L2 in Linux 2.6.34</title>
      <orderedlist>
	<listitem>
	  <para>Added
<constant>V4L2_CID_IRIS_ABSOLUTE</constant> and
<constant>V4L2_CID_IRIS_RELATIVE</constant> controls to the
	    <link linkend="camera-controls">Camera controls class</link>.
	  </para>
	</listitem>
      </orderedlist>
2340
    </section>
2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351
    <section>
      <title>V4L2 in Linux 2.6.37</title>
      <orderedlist>
	<listitem>
	  <para>Remove the vtx (videotext/teletext) API. This API was no longer
used and no hardware exists to verify the API. Nor were any userspace applications found
that used it. It was originally scheduled for removal in 2.6.35.
	  </para>
	</listitem>
      </orderedlist>
    </section>
2352
    <section>
2353
      <title>V4L2 in Linux 2.6.39</title>
2354
      <orderedlist>
2355 2356 2357
        <listitem>
          <para>The old VIDIOC_*_OLD symbols and V4L1 support were removed.</para>
        </listitem>
2358 2359 2360 2361 2362 2363 2364 2365
        <listitem>
          <para>Multi-planar API added. Does not affect the compatibility of
          current drivers and applications. See
          <link linkend="planar-apis">multi-planar API</link>
          for details.</para>
        </listitem>
      </orderedlist>
    </section>
2366 2367 2368 2369 2370 2371 2372 2373 2374 2375
    <section>
      <title>V4L2 in Linux 3.1</title>
      <orderedlist>
        <listitem>
	  <para>VIDIOC_QUERYCAP now returns a per-subsystem version instead of a per-driver one.</para>
	  <para>Standardize an error code for invalid ioctl.</para>
          <para>Added V4L2_CTRL_TYPE_BITMASK.</para>
        </listitem>
      </orderedlist>
    </section>
2376 2377 2378 2379 2380 2381
    <section>
      <title>V4L2 in Linux 3.2</title>
      <orderedlist>
        <listitem>
	  <para>V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to userspace.</para>
        </listitem>
2382
        <listitem>
2383 2384 2385 2386 2387
	  <para>Add selection API for extended control over cropping
	  and composing. Does not affect the compatibility of current
	  drivers and applications. See <link
	  linkend="selection-api"> selection API </link> for
	  details.</para>
2388
        </listitem>
2389 2390
      </orderedlist>
    </section>
2391

2392 2393 2394 2395 2396 2397 2398 2399
    <section>
      <title>V4L2 in Linux 3.3</title>
      <orderedlist>
        <listitem>
	  <para>Added <constant>V4L2_CID_ALPHA_COMPONENT</constant> control
	    to the <link linkend="control">User controls class</link>.
	  </para>
        </listitem>
2400 2401 2402 2403
        <listitem>
	  <para>Added the device_caps field to struct v4l2_capabilities and added the new
	  V4L2_CAP_DEVICE_CAPS capability.</para>
        </listitem>
2404 2405 2406
      </orderedlist>
    </section>

2407 2408 2409 2410 2411 2412 2413
    <section>
      <title>V4L2 in Linux 3.4</title>
      <orderedlist>
        <listitem>
	  <para>Added <link linkend="jpeg-controls">JPEG compression control
	  class</link>.</para>
        </listitem>
2414 2415 2416 2417 2418
        <listitem>
	  <para>Extended the DV Timings API:
	  &VIDIOC-ENUM-DV-TIMINGS;, &VIDIOC-QUERY-DV-TIMINGS; and
	  &VIDIOC-DV-TIMINGS-CAP;.</para>
        </listitem>
2419 2420 2421
      </orderedlist>
    </section>

2422 2423 2424 2425 2426 2427 2428
    <section>
      <title>V4L2 in Linux 3.5</title>
      <orderedlist>
        <listitem>
	  <para>Added integer menus, the new type will be
	  V4L2_CTRL_TYPE_INTEGER_MENU.</para>
        </listitem>
2429 2430 2431 2432 2433
        <listitem>
	  <para>Added selection API for V4L2 subdev interface:
	  &VIDIOC-SUBDEV-G-SELECTION; and
	  &VIDIOC-SUBDEV-S-SELECTION;.</para>
        </listitem>
2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446
        <listitem>
	  <para> Added <constant>V4L2_COLORFX_ANTIQUE</constant>,
	  <constant>V4L2_COLORFX_ART_FREEZE</constant>,
	  <constant>V4L2_COLORFX_AQUA</constant>,
	  <constant>V4L2_COLORFX_SILHOUETTE</constant>,
	  <constant>V4L2_COLORFX_SOLARIZATION</constant>,
	  <constant>V4L2_COLORFX_VIVID</constant> and
	  <constant>V4L2_COLORFX_ARBITRARY_CBCR</constant> menu items
	  to the <constant>V4L2_CID_COLORFX</constant> control.</para>
        </listitem>
        <listitem>
	  <para> Added <constant>V4L2_CID_COLORFX_CBCR</constant> control.</para>
        </listitem>
2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461
        <listitem>
	  <para> Added camera controls <constant>V4L2_CID_AUTO_EXPOSURE_BIAS</constant>,
	  <constant>V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE</constant>,
	  <constant>V4L2_CID_IMAGE_STABILIZATION</constant>,
	  <constant>V4L2_CID_ISO_SENSITIVITY</constant>,
	  <constant>V4L2_CID_ISO_SENSITIVITY_AUTO</constant>,
	  <constant>V4L2_CID_EXPOSURE_METERING</constant>,
	  <constant>V4L2_CID_SCENE_MODE</constant>,
	  <constant>V4L2_CID_3A_LOCK</constant>,
	  <constant>V4L2_CID_AUTO_FOCUS_START</constant>,
	  <constant>V4L2_CID_AUTO_FOCUS_STOP</constant>,
	  <constant>V4L2_CID_AUTO_FOCUS_STATUS</constant> and
	  <constant>V4L2_CID_AUTO_FOCUS_RANGE</constant>.
	  </para>
        </listitem>