[alsa-devel] Asynchronous audio USB chips: choppy playback since 3.8-rc7
zonque at gmail.com
Wed Apr 3 17:00:32 CEST 2013
On 03.04.2013 16:11, Michael Trimarchi wrote:
> On 03/04/13 15:55, Michael Trimarchi wrote:
>> 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.
Is OMAP3 at all a platform that is affected by the bug? It seems the
effect is only seen on some special host controller hardware anyway.
> 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
Sorry, you lost me. So what's the status of this issue now? Does "USB:
EHCI: fix bug in iTD/siTD DMA pool allocation" fix it?
If not - and assuming you can reproduce the bug - which patches of the
two I mentioned did you revert, and what was the effect of that? Did you
try and remove both as well?
More information about the Alsa-devel