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authorKeith Winstein <keithw@cs.stanford.edu>2020-10-25 22:05:47 -0700
committerTakashi Iwai <tiwai@suse.de>2020-10-27 08:25:04 +0100
commitf15cfca818d756dd1c9492530091dfd583359db3 (patch)
tree3342ec4c247a15b3d3d6be41a9900f7a604ad24e /sound/usb
parent2a6eca16f376f6b83aaf73c57f0b6547907a5ed3 (diff)
ALSA: usb-audio: Add implicit feedback quirk for Zoom UAC-2
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>
Diffstat (limited to 'sound/usb')
-rw-r--r--sound/usb/pcm.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index b401ee894e1b..31b1edf53c41 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -352,6 +352,10 @@ static int set_sync_ep_implicit_fb_quirk(struct snd_usb_substream *subs,
ep = 0x81;
ifnum = 2;
goto add_sync_ep_from_ifnum;
+ case USB_ID(0x1686, 0xf029): /* Zoom UAC-2 */
+ ep = 0x82;
+ ifnum = 2;
+ goto add_sync_ep_from_ifnum;
case USB_ID(0x1397, 0x0001): /* Behringer UFX1604 */
case USB_ID(0x1397, 0x0002): /* Behringer UFX1204 */
ep = 0x81;