[mythtv-users] WriteAudio: buffer underruns without prebuffering pauses (SOLVED - almost)

Steven Adeff adeffs.mythtv at gmail.com
Thu Feb 22 14:50:28 UTC 2007

On 2/22/07, Tom Greer <trgreer at gmail.com> wrote:
> Last night I had an opportunity to experiment. Here are my results.
> My baseline setup was:
> Extra Audio Buffering: On
> Aggressive Sound Card Buffering: Off
> XVMC: Off
> With this setup, on my test recording (The Closer episode from TNT-HD
> @ 1080i) I incurred a "WriteAudio: buffer underrun" at a rate of just
> under 1 per secord.  The CPU ran at about 93% busy.
> Turning on Extra Audio Buffering resulted in prebuffering pauses at a
> rate of about 2 per second - and the audio buffer underruns
> disappeared.  CPU: 93%
> Turning on the Aggressive Buffering made no difference with or without
> Extra Audio Buffering and with or without XVMC.
> Turning on XVMC dropped the CPU load to about 30%; but the number of
> audio buffer underruns (with extra buffering off) or the number of
> prebuffering pauses (with extra buffering on) was unchanged.
> Next I changed the "NVAGP" option in my xorg.conf file from 2 to 3 to
> force NvAGP to load in place of AGPGART.  Result: no change.
> Next up: I modified the "Enable OpenGL vertical sync for timing"
> option from on to off.  Result: no audio buffer underruns and no
> prebuffer pauses.  CPU load increased to 95+%.
> YES!!!
> One final test.  The Fifth Element recorded @ 1080i always seems to
> work the system harder than any other recording.  Audio stuttering
> returns.
> At least this setup let's us watch most HD recordings.  I'm sure it
> will work well on chick flicks - and only fail on action adventure
> movies...
> I'm mystified as to why XVMC was successful in dropping the CPU load
> but did not make the prebuffering pauses/audio buffer underruns go
> away.  But I am not a fan of XVMC (choppy fast forward/rewind, video
> glitches, other anomolies) anyway, and I am not inclined to spend a
> lot of time trying to make it work.  Of course, if someone has a
> simple fix, I'd love to hear it.
> My next step: Convince wifey to let me move this frontend box to that
> old projection TV in the living room and build a new box with more CPU
> horsepower for the plasma screen.

which nvidia driver are you using?
(p.s. jealous you can record TNT-HD...)

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