On Fri, 19 Apr 2013, Daniel Mack wrote: > On 03.04.2013 12:25, Takashi Iwai wrote: > > At Wed, 03 Apr 2013 12:15:25 +0200, > > David Henningsson wrote: > >> > >> Hi ALSA developers, > >> > >> Just to get your attention here on what seems to be an USB audio > >> regression. > >> > >> The bug is described in detail here: > >> > >> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all > >> > >> Quoting the bug: > >> > >> " > >> This bug seems to affect only a certain kind of hardware, which is > >> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such > >> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so > >> called "Synchronous USB DAC", uses the clock hosted by the mother board, > >> which is not affected by this bug. > >> > >> When this bug affects an asynchronous USB DAC, the audio played by the > >> DAC is constantly interrupted. The playback itself does not stop, but > >> the output becomes discontinous, filling with constant crackling noises, > >> destroying everything the DAC plays. > >> " > >> > >> According to the bug reporter, which seems to have done quite a bit of > >> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable > >> kernels and the bug also lists a few commits which could be the cause, > >> none under sound/usb though. > > > > Yes, there is no commits regarding usb-audio itself between 3.8-rc6 > > and rc7, so the likely culprit is in drivers/usb (usually either > > drivers/usb/host or drivers/usb/core). There are a bunch of changes > > there, so further bisection would be appreciated. > > Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan > relentlessly tested all of them, and it turns out that > > 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers") > > Is the first bad commit. Also, reverting this commit from the current > mainline head makes the problem disappear. > > Alan, any idea? > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110
No ideas as to the cause. For debugging, it would help to see a usbmon trace from a kernel where the problem occurs, together with a trace from another kernel where the problem does not occur. Alan Stern -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1136110 Title: USB Audio Codec choppy playback To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
