[mythtv] Re: ALSA "fixes" actually break stuff in CVS?

[Terry Barnaby]

Hi,

Some more info on this.
With the "soundcard_buffer_size = info.bytes;" line in the code,
which looks correct to me, my system exhibits bi-stable
behaviour.

Sometimes MythTv runs fine without juddering and sometimes
it starts this juddering. It seems that there is an unstable
timing control issue in "AudioOutputBase::OutputAudioLoop".
This would be affected by other timings, hence others may
not see the problem ...

When juddering the CPU usage goes from about 18% to 95%.
One little point, which may not be related, I am running MythTv
as root. This means that some threads are running as real-time
threads. I believe that a small usleep() in a real-time thread
is implemented as a CPU loop ...

I will further delve into this issue as time permits.

Terry

Terry Barnaby wrote:
> Hi,
> 
> I have narrowed down the problem to the changes from MythTv
> CVS 2004-11-29 to 2004-11-30.
> 
> I have further narrowed this down to the file:
> 
> libs/libmyth/audiooutputoss.cpp, Line: 112
> 
> "soundcard_buffer_size = info.bytes;"
> 
> This line was added in 2004-11-30. On my system this sets
> soundcard_buffer_size from 0 to 65536.
> 
> If I remove this line the "juddering" goes away ....
> 
> Note that my system is currenly using the OSS driver, although
> I had the same problem with the ALSA driver.
> 
> Terry
> 
> Ed Wildgoose wrote:
> 
>>
>>> The other other one on that same day at a different time was
>>> mythtv/libs/libmyth/audiooutputbase.cpp .
>>
>>
>>
>>
>> Thanks, yes I saw that when I was editing the audio code.  I had to 
>> get my calculator out and have a think if it was sensible or not and 
>> nearly reversed it actually.  Doesn't cause me any problems though.  
>> In retrospect, at least in theory, the audio loop changes seemed quite 
>> sensible and reasonable even in the case of my funny pro audio card, 
>> but hey just occured to me that it might be related to the jerky 
>> output reports...
>>
>> Any of you folks having trouble actually tried this yet?
>>
>>
>>
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> 
> 
> 
> 
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