В Пн, 08/06/2020 в 15:35 +0200, Takashi Iwai пишет: > On Mon, 08 Jun 2020 10:32:24 +0200, > Thomas Ebeling wrote: > > > > On 08.06.20 09:19, Takashi Iwai wrote: > > > 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. > > > > > > > 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. > > > > Since I recently had clock drift issues with Audient devices, I'm > > intrigued by this. @Takashi Can you quickly elaborate, what you > > think, > > Laurance's issue might be and what has changed in that tree that > > might > > help him fix it? Is there some general issue with the current > > (stable) > > sound/usb implementation? > > The frame size calculation in USB-audio driver wasn't accurate enough > because of the computation in Q16.16 format. It works OK for async > mode, but for others, it can accumulate rounding errors. The recent > change corrected it for a more precise way. I believe that SSL and Audient devices operates in async mode. Would be nice to see "lsusb -v" output for them.
