• Torstein Hegge's avatar
    ALSA: usb: Work around CM6631 sample rate change bug · 690a863f
    Torstein Hegge authored
    The C-Media CM6631 USB receiver doesn't respond to changes in sample rate
    while the interface is active. The same behavior is observed in other UAC2
    hardware like the VIA VT1731.
    Reset the interface after setting the sampling frequency on sample rate
    changes, to ensure that the sample rate set by snd_usb_init_sample_rate() is
    used. Otherwise, the device will try to use the sample rate of the previous
    stream, causing distorted sound on sample rate changes.
    The reset is performed for all UAC2 devices, as it should not affect a
    standards compliant device, but it is only necessary for C-Media CM6631,
    VIA VT1731 and possibly others.
    Failure to read sample rate from the device is not handled as an error in
    set_sample_rate_v2(), as (permanent or intermittent) failure to read sample
    rate isn't essential for a successful sample rate set.
    Signed-off-by: default avatarTorstein Hegge <hegge@resisty.net>
    Acked-by: default avatarClemens Ladisch <clemens@ladisch.de>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
clock.c 9.77 KB