[mythtv] No Start with Pulse Audio (Changeset 20310)

[Michael Drons]

________________________________
From: Ed W <lists at wildgooses.com>
To: Development of mythtv <mythtv-dev at mythtv.org>
Sent: Thursday, April 23, 2009 3:18:13 PM
Subject: Re: [mythtv] No Start with Pulse Audio (Changeset 20310)

Daniel Kristjansson wrote: 
On Sun, 2009-04-12 at 23:53 +0100, Colin Guthrie wrote:

If there is anything I can do here, please let me know. I do quite a bit 
of hacking on pulseaudio, so any problem you're having, I can try and 
sort things out.
I certainly believe that a better solution than just exiting when pulse 
is enabled can be found!

Colin the problem is very large latencies. This is especially a problem
with Ubuntu, and especially with the as of yet unreleased version called
jaunty which makes it difficult for regular users to remove pulseaudio
and which sets pulseaudio up as providing the ALSA default interface.


Is there a specific problem with the pulseaudio support patch? If so, 
perhaps I can help make it better if I can be told what's wrong. Would 
detecting pulse and switching to that output system be acceptable?

There is nothing wrong with the patch per say, but the existing patch
doesn't do anything for the latencies when using pulse audio. Not that
I would expect it to.

I have started working on a solution basically it will disable
pulseaudio by default if the audio server is local, but also allow
you to explicitly enable pulseaudio should you really want it.

Forgive joining in 2 weeks later, but the issue seems to be unrelated
to pulseaudio or myth - the issue seems to be just kernel scheduling
being way off the mark on some kernels. Actually it seems surprising
that myth works at all reliably under these conditions either - if busy
wait loops are being serviced at 1/5 second kind of intervals then
likely plenty more things are going to go wrong than the relatively
small problem of feeding the audio server with a small amount of data?

I'm baffled that people get so excited about audio APIs.  They nearly
all work in roughly the same manner and you just feed them data on a
regular basis - I personally can't see a huge bunch of difference
between OSS, Alsa, Jack, RtAudio - they all work roughly the same from
the point of view of handing off the audio.  They all seem to have
various boring implementation details of setting up the interface (Alsa
being my least favourite from that point of view...), and they all seem
to have a ton a bugs due to implementation problems with the low level
drivers (but that's hardly the specific fault of the upper layers -
trying to get a stable permutation of buffer size and periods in Alsa
is one of the more fun games...)

Anyway, sounds like the issue is change the kernel more than change the
software?

Just to put my stake in the ground, I am a Jack user running without
problem at a mere two periods of 256 samples (it runs fine at 2x 64
samples also), which is around 5ms latency (I also burn a ton of CPU at
the same time using resampling and Brutefir doing some massive
convolution filters).  I had hoped to switch to Pulseaudio at some
point and eliminate Jack since the features of Pulse look pretty nice. 
Here's hoping that support isn't dropped, just that the instructions
warn people about getting the kernel sorted...

Good luck

Ed W

__________________________________________


What about windows?  I see this message when trying to start mythfrontend in Windows XP.   Myth was built from the 20404 version of trunk.  I am trying to rebuild with the latest version.

Mike


      
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