From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7 Date: Wed, 03 Apr 2013 12:23:14 +0200 Message-ID: <515C0312.1090507@gmail.com> References: <515C013D.8090909@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bk0-f48.google.com (mail-bk0-f48.google.com [209.85.214.48]) by alsa0.perex.cz (Postfix) with ESMTP id 74E2726535C for ; Wed, 3 Apr 2013 12:23:17 +0200 (CEST) Received: by mail-bk0-f48.google.com with SMTP id jf3so702878bkc.7 for ; Wed, 03 Apr 2013 03:23:17 -0700 (PDT) In-Reply-To: <515C013D.8090909@canonical.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: David Henningsson Cc: Takashi Iwai , Clemens Ladisch , "alsa-devel@alsa-project.org" , Alan Stern , 1136110@bugs.launchpad.net List-Id: alsa-devel@alsa-project.org 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 > 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. 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 for testing? Thanks, Daniel