[alsa-devel] Asynchronous audio USB chips: choppy playback since 3.8-rc7
zonque at gmail.com
Wed Apr 3 12:23:14 CEST 2013
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"
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
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