[alsa-devel] Asynchronous audio USB chips: choppy playback since 3.8-rc7
michael at amarulasolutions.com
Wed Apr 3 16:11:39 CEST 2013
On 03/04/13 15:55, Michael Trimarchi wrote:
> Hi Daniel
> On 03/04/13 12:23, Daniel Mack wrote:
>> Hi David,
>> On 03.04.2013 12:15, David Henningsson wrote:
>>> Just to get your attention here on what seems to be an USB audio
>>> The bug is described in detail here:
>>> 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.
>> There were no relevant changes for snd-usb between the two versions
>> mentioned. The only patches that come in mind in this time window are:
>> 3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>> b09a61cc0 "USB: EHCI: fix for leaking isochronous data"
> This last one, doesn't give me any problem, just a memory leak and not a choppy
> playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
> think that it can be the reason of the problem.
Sorry the comment was for a bug that is not included in this list and recently fixed.
USB: EHCI: fix bug in iTD/siTD DMA pool allocation
>> And they have both been back-ported to stable. Copied Alan for reference.
>> Any chance some of the bug reporters could try and revert exactly those
>> for testing?
>> Alsa-devel mailing list
>> Alsa-devel at alsa-project.org
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