Bug#687045: pulseaudio: Audio delay and crackling at startup

[Felipe Sateler]

Copying back the bug log with some side conversations between David and me:


David wrote:
On 04/22/2014 06:16 PM, Felipe Sateler wrote:

> On Fri, Apr 18, 2014 at 8:15 PM, David Smith <sidicas2 at gmail.com> wrote:
> > On 04/18/2014 06:01 PM, Felipe Sateler wrote:
> >>
> >> This may be a problem of too high CPU usage. Can you try changing the
> >> resample-method key in daemon.pa?
> >>
> >> I think the 'trivial' resampler should be the less cpu-hungry, so you
> >> should probably try that first.
> >>
> >
> > That doesn't make any sense though, my laptop is an 8-core laptop that's
> > sitting idle almost all the time when the crackling/popping happens.
> >
> > It *COULD* be something related to the frequency of my CPU changing..  I
> > realized that the new intel power management stuff is clocking my CPU
> > all over the place.. In the old days it would only cycle between 3 or 4
> > different frequencies and it would be very slow about reclocking.. Now
> > it's almost instantaneous reclocking of the CPU to save power and it's
> > got a lot of different frequencies it can clock to..
> >
> > If I set my CPU to a fixed frequency, either the lowest or the highest
> > possible frequency the CPU supports, the entire problem disappears.
>
> Possibly the cpu frequency changes cause pulseaudio or alsa to loose sync.
>
> >
> > But I'm not going to run my CPU on a fixed frequency like that because
> > it's always either inconveniently slow or a power hog.  So I need to use
> > the configuration change to pulseaudio described above which seems to
> > fix the problem entirely.
>
> By the configuration change you mean the one I suggested or the tsched
> one you suggested earlier in the bug report?
tsched=0



And I wrote:
On Wed, Apr 23, 2014 at 6:54 PM, David Smith <sidicas2 at gmail.com> wrote:
> On 04/23/2014 04:43 PM, David Smith wrote:
>> The other really weird thing about it.. Whenever I seek in a
>> audio/video file.. It will start crackling for a little bit and then
>> go away.. And it happens everytime I seek no matter where in the file
>> I go. Also if I play an audio file that's 30 mins long, it only
>> crackles for the first 1-10 seconds or so and runs fine after that no
>> matter what other things I do on the PC. -David
>
> That's why I thought it had something to do with the CPU clocking.
> When you seek in an audio/video track, it causes the CPU usage to spike
> and the CPU gets reclocked.
> But I've got an 8-core Ivy Bridge CPU here, it's not a problem of the
> CPU being too slow.
>
> When I set my CPU to a single frequency so it's not scaling up and down
> to save power, then the crackling is almost completely gone.. Not
> entirely though, but it also slaughters my battery life so it's not
> worth it at all.
>
> So the best solution, by far, is tsched=0 and make sure all my power
> management is enabled.


Hmm, so we should probably document this in the README.Debian too.

On Wed, Apr 23, 2014 at 9:51 PM, David Smith <sidicas2 at gmail.com> wrote:
> On 04/23/2014 05:25 PM, Felipe Sateler wrote:
>> Hmm, so we should probably document this in the README.Debian too. Do
>> you mind if forward this discussion back to the log?
> Well..  I just installed 4.0-6~bpo7+1 of pulseaudio and made sure it
> overwrote my config files.
> There's no tsched=0 in there, I did a reboot and I'm not hearing any
> crackling.
>
> I know i've installed the backport of pulseaudio shortly after wheezy
> came out and it still had crackling.. This must have fixed it within the
> past year or so.
>
> Gonna try a few games and report back in a few days.
>
> I knew it was pulseaudio and not the drivers :D.
>
> -David
>
>



-- 

Saludos,
Felipe Sateler