On Tue, 29 Nov 2022 14:00:59 +0100, John Keeping wrote: > > Tascam's Model 12 is a mixer which can also operate as a USB audio > interface. The audio interface uses explicit feedback but it seems that > it does not correctly handle missing isochronous frames. > > When injecting an xrun (or doing anything else that pauses the playback > stream) the feedback rate climbs (for example, at 44,100Hz nominal, I > see a stable rate around 44,099 but xrun injection sees this peak at > around 44,135 in most cases) and glitches are heard in the audio stream > for several seconds - this is significantly worse than the single glitch > expected for an underrun. > > While the stream does normally recover and the feedback rate returns to > a stable value, I have seen some occurrences where this does not happen > and the rate continues to increase while no audio is heard from the > output. I have not found a solid reproduction for this. > > This misbehaviour can be avoided by totally resetting the stream state > by switching the interface to alt 0 and back before restarting the > playback stream. > > Add a new quirk flag which forces the endpoint and interface to be > reconfigured whenever the stream is stopped, and use this for the Tascam > Model 12. > > Separate interfaces are used for the playback and capture endpoints, so > resetting the playback interface here will not affect the capture stream > if it is running. While there are two endpoints on the interface, > these are the OUT data endpoint and the IN explicit feedback endpoint > corresponding to it and these are always stopped and started together. > > Signed-off-by: John Keeping <john@xxxxxxxxxxxx> > --- > v2: > - Set ep->need_prepare not ep->need_setup; this was missed when forward > porting the patch as need_prepare is new in 6.1 > - Add more details to the commit message about why it is safe to reset > the interface here Thanks, applied now. Takashi
