]> git.proxmox.com Git - mirror_ubuntu-focal-kernel.git/commit
ALSA: usb-audio: Add implicit feedback quirk for Zoom UAC-2
authorKeith Winstein <keithw@cs.stanford.edu>
Mon, 26 Oct 2020 05:05:47 +0000 (22:05 -0700)
committerStefan Bader <stefan.bader@canonical.com>
Thu, 10 Dec 2020 11:05:49 +0000 (12:05 +0100)
commitcc5f9d00937b1ac3f989f38ce2893f771f3aa70d
treebd7b1da62080973c16a83d0adb6e6046986e09a5
parentdd1e9b2c9eb61d11b15b82431079a085f59788ae
ALSA: usb-audio: Add implicit feedback quirk for Zoom UAC-2

BugLink: https://bugs.launchpad.net/bugs/1905612
commit f15cfca818d756dd1c9492530091dfd583359db3 upstream.

The Zoom UAC-2 USB audio interface provides an async playback endpoint
("1 OUT (ASYNC)") and capture endpoint ("2 IN (ASYNC)"), both with
2-channel S32_LE in 44.1, 48, 88.2, 96, 176.4, or 192
kilosamples/s. The device provides explicit feedback to adjust the
host's playback rate, but the feedback appears unstable and biased
relative to the device's capture rate.

"alsaloop -t 1000" experiences playback underruns and tries to
resample the captured audio to match the varying playback
rate. Forcing the kernel to use implicit feedback appears to
produce more stable results. This causes the host to transmit one
playback sample for each capture sample received. (Zoom North America
has been notified of this change.)

Signed-off-by: Keith Winstein <keithw@cs.stanford.edu>
Tested-by: Keith Winstein <keithw@cs.stanford.edu>
Cc: <stable@vger.kernel.org>
BugLink: https://lore.kernel.org/r/20201027071841.GA164525@trolley.csail.mit.edu
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
sound/usb/pcm.c