Tracks only partially playing - SOLVED

[Colin Guthrie]

'Twas brillig, and Jeff Mitchell at 29/07/09 21:40 did gyre and gimble:
> Anne Wilson wrote:
>> On Wednesday 29 July 2009 18:39:17 Anne Wilson wrote:
>>> Just seen this on the Fedora user list:
>>> <quote>
>>> when I play a Mp3 file, Rhythmbox starts at the right speed and then
>>> it starts very fast playing....what is going on??? who is causing this
>>> mess??? and this is not rawhide :-(
>>> </quote>
>>> So a gnome app and amarok are experiencing the same thing!  Obviously
>>> something at a deeper level, then.
>>>
>> In case a bug-hunter finds this in the archives -
>>
>> It's an alsa bug -https://bugzilla.redhat.com/show_bug.cgi?id=514213
>>
>> The work-around is to edit /etc/pulse/default.pa,
> 
> Ah hah! PulseAudio, the very first suspect  :-) I didn't realize Fedora
> was also taking part in the craziness, not just Ubuntu.

Fedora are pioneering it!! RedHat employ the main developer, Nokia, 
Palm, Intel and others all contribute in some capacity too. Ubuntu too 
are currently hiring for a position in this area.

Ubuntu just followed the Redhat lead and didn't copy it all that well 
during the initial stages with a really half baked effort - and in an 
LTS release! This has really clouded many peoples opinions of pulseaudio 
- without a real basis of where the real problem lies or why pulseaudio 
is needed and desirable - which is why I'm personally p155ed off about 
it. Thankfully Ubuntu learned the hard way about it and it's much better 
these days, tho' still some way to go.

I'm not sure that any other distro other than Mandriva provides a handy 
ticky box in the sound config tool to tweak this specific option for you 
(and for those of you who really want to, you can disable PA completely 
there too).

In Mandriva, just going into draksound and tick the box titled:
  Disable glitch-free mode.

Simple, eh? That will add the tsched=0 option for, not that hard to do, 
but much more user friendly than editing config files. Another reason 
why a pulseaudio rollout in a distro should be very carefully managed 
and not taken half heartedly.


Anyway back to the point, FWIW, this is 100% an ALSA error, not PulseAudio.

The ALSA driver is providing totally inaccurate timing information and 
when that happens there is not much PulseAudio can do.

The change if setting in PulseAudio enables a legacy mode that relies on 
the more reliable but battery draining interrupt driven mode.

To learn more about glitch free mode, why it's a good thing and why the 
driver layer needs fixed to really use this properly please read here:
http://0pointer.de/blog/projects/pulse-glitch-free.html

It's a very interesting read, and well worth the 10 minutes you'd invest 
in reading it.

Col

-- 

Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/

Day Job:
   Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
   Mandriva Linux Contributor [http://www.mandriva.com/]
   PulseAudio Hacker [http://www.pulseaudio.org/]
   Trac Hacker [http://trac.edgewall.org/]