On Sun, 07 Jun 2020 15:39:59 +0200, Laurence Tratt wrote:
Hello,
I've found an interesting issue with an SSL2+ audio interface -- it plays and records fine (and, for the money, the sound quality is excellent!), but recording slowly but surely drifts over time. For example, if I record a click track in Audacity (or Ardour), play it through the interface and record it, and then line up the start of the recorded click track with the original, the two tracks will be around 5ms out of alignment after 30s. Interestingly, this problem does not happen with OpenBSD, where the two tracks line up precisely.
My guess is that the problem is to do with implicit feedback in endpoints. I wondered if the problem was the same as with the MOTU M4, but enabling that quirk for the SSL2+ introduced some crackle, but didn't change the drift.
I'm attaching a) the alsa-info file b) output from OpenBSD's kernel with debugging in the USB audio driver turned on in case that gives some clues as to what the two OS's and drivers might be doing differently. If anyone has any suggestions for how this problem might be addressed, I would be very grateful!
The recent change in USB-audio might help for a case like yours. Try my sound git tree (for-linus branch) or Linus' tree. The former should be pullable onto 5.7 kernel cleanly.
thanks,
Takashi