Re: snd-usb: "delay: estimated 0, actual 352"

From: Markus Trippelsdorf <markus@trippelsdorf.de>
To: Daniel Mack <zonque@gmail.com>
Cc: Takashi Iwai <tiwai@suse.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Subject: Re: snd-usb: "delay: estimated 0, actual 352"
Date: Thu, 6 Sep 2012 09:17:57 +0200	[thread overview]
Message-ID: <20120906071757.GB257@x4> (raw)
In-Reply-To: <50484BEB.4020103@gmail.com>

On 2012.09.06 at 09:08 +0200, Daniel Mack wrote:
> On 06.09.2012 08:53, Markus Trippelsdorf wrote:
> > On 2012.09.06 at 08:48 +0200, Takashi Iwai wrote:
> >> At Thu, 06 Sep 2012 08:33:30 +0200,
> >> Daniel Mack wrote:
> >>>
> >>> On 06.09.2012 08:02, Markus Trippelsdorf wrote:
> >>>> On 2012.09.04 at 16:40 +0200, Takashi Iwai wrote:
> >>>>> ----------------------------------------------------------------
> >>>>> Sound fixes for 3.6-rc5
> >>>>>
> >>>>> There are nothing scaring, contains only small fixes for HD-audio and
> >>>>> USB-audio:
> >>>>> - EPSS regression fix and GPIO fix for HD-audio IDT codecs
> >>>>> - A series of USB-audio regression fixes that are found since 3.5 kernel
> >>>>>
> >>>>> ----------------------------------------------------------------
> >>>>> Daniel Mack (4):
> >>>>>       ALSA: snd-usb: Fix URB cancellation at stream start
> >>>>>       ALSA: snd-usb: restore delay information
> >>>>         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
> >>>> The commit fbcfbf5f above causes the following lines to be printed
> >>>> whenever I start a new song:
> >>>
> >>> Copied Pierre-Louis Bossart - he wrote the code in 294c4fb8 which this
> >>> patch (fbcfbf5f) brings back now.
> >>>
> >>>> delay: estimated 0, actual 352
> >>>> delay: estimated 353, actual 705
> >>>>
> >>>> (44.1 * 8 = 352.8)
> >>>>
> >>>> This happens with an USB-DAC that identifies itself as "C-Media USB
> >>>> Headphone Set".
> >>>
> >>> And you didn't you see these lines with 3.4?
> >>
> >> Maybe the difference of start condition?
> >>
> >> Markus, does the patch below fix anything?
> > 
> > Unfortunately no.
> > However reverting the following fixes the problem:
> > 
> > commit 245baf983cc39524cce39c24d01b276e6e653c9e
> > Author: Daniel Mack <zonque@gmail.com>
> > Date:   Thu Aug 30 18:52:30 2012 +0200
> > 
> >     ALSA: snd-usb: fix calls to next_packet_size
> > 
> 
> No, this one certainly fixes a problem and does the right thing by
> restoring the original code.
> 
> If you wouldn't state that you didn't see the same effect with 3.4(!),
> before the refactoring done in 3.5, I would believe the device is simply
> slightly off in its feedback rate and the tighter delay code complains
> about it while compensating, just as it did before.
> 
> Are there any more than these two lines? And is audio working at all? Is
> it distorted in any way?

There are only these two lines (printed whenever sound starts). Audio is
working just fine with no distortions.

I did see similar lines before when the system load was very high
(happend during "make check" when building glibc).

Here is what Pierre-Louis wrote in November 2011:

Â»This was supposed to be an informational message, I thought it was only
enabled for debug. Regular users don't really need to know.Â«

-- 
Markus