[mythtv] Prebuffering pause / Broadcasting free space avail / audio waiting for buffer to fill

Gee, David david at allpowerfuldave.com
Tue Jun 27 20:48:36 UTC 2006


Hi all

I've posted on this subject before but not got very far, and I am keen
to get to the bottom of this as it's a headache to watch TV at the
moment. Last time I assumed that the problems I was having were an
artifact of running dual-head, which I have now eliminated as a
possibility by testing in single-head mode. The problem I have is that
when either watching live TV or viewing recordings, I get about a second
or so's video and audio (correctly in sync), then a silent gap of a
couple of seconds (with a frozen picture), then the next second or so of
video and audio. So whenever it plays, it's in sync, and the stuff it
plays is correct, there's just these irritating two second (or so) gaps
every three seconds or so.

Digging some further, this is the sort of output I get from mythfrontend
-v all:

2006-06-27 21:32:11.952 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.953 Broadcasting free space avail
2006-06-27 21:32:11.959 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.959 Broadcasting free space avail
2006-06-27 21:32:11.963 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.963 Broadcasting free space avail
2006-06-27 21:32:11.967 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.967 Broadcasting free space avail
2006-06-27 21:32:11.973 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.973 Broadcasting free space avail
2006-06-27 21:32:11.979 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.979 Broadcasting free space avail
2006-06-27 21:32:11.983 audio waiting for buffer to fill: have 3072 want
4096
2006-06-27 21:32:11.983 Broadcasting free space avail

with various other messages such as

2006-06-27 21:31:51.917 NVP: Audio is 3.81795 frames ahead of video,
                        doubling video frame interval.
2006-06-27 21:31:51.918 NVP: Audio is 4.6072 frames ahead of video,
                        doubling video frame interval.

and

2006-06-27 20:31:12.752 NVP: Waiting for prebuffer.. 1
UuAAAAAAAAAAAAAAAAAAAAAAUUuUULA
2006-06-27 20:31:12.918 NVP: Waiting for prebuffer.. 2
UULAAAAAAAAAAAAAAAAAAAAAUUUUUuA
2006-06-27 20:31:16.318 NVP: prebuffering pause
2006-06-27 20:31:16.318 NVP: Waiting for prebuffer.. 0
AAAAAAAAAAAAAALAALAAAAUAAAAAAAA
2006-06-27 20:31:29.297 NVP: prebuffering pause
2006-06-27 20:31:29.297 NVP: Waiting for prebuffer.. 0
AAAAAAAAAAAAAAuAALAAAAAAAAAAAAA
2006-06-27 20:31:39.016 NVP: prebuffering pause
2006-06-27 20:31:39.016 NVP: Waiting for prebuffer.. 0
AAAALAAAAAAAAAAAAAAAAAAAAaLAAAU
2006-06-27 20:31:42.298 NVP: prebuffering pause
2006-06-27 20:31:42.298 NVP: Waiting for prebuffer.. 0
AAAAAAAAAAAAAALAALAAAAAAAAAAUAA
2006-06-27 20:31:48.723 NVP: prebuffering pause
2006-06-27 20:31:48.723 NVP: Waiting for prebuffer.. 0
AAaAALAAAAAAAAAAAAAAAuAAAAAAAAA
2006-06-27 20:31:51.984 NVP: prebuffering pause
2006-06-27 20:31:51.984 NVP: Waiting for prebuffer.. 0
AAALAAAAAUAAAAAAAaALAAAAAAAAAAA

I've tried all the various decoders (Std, Std XvMc, VIA XvMC, libmpeg2),
and also tried fiddling with all the obvious options (aggressive audio
buffering, realtime threads, interlacing, and so on), all to no avail.
The only thing that makes some sense was one comment I got back that it
was maybe some incompatibility with the X.org radeon driver (I have an
ATI Radeon 9200SE using the standard radeon driver), although given that
MythTV *used* to work without these problems on this exact same hardware
about a year ago under FC4 (I'm now running FC5), I'd be surprised if
that was it.

I'm confident that it's not a driver problem (ivtv), for two reasons:
playing /dev/video0 with mplayer directly is perfect, and playing mpg
files recorded by myth in an external program such as xine is also
perfect. So mythtv is getting the video data correctly, it's somewhere
between there and the screen that things go awry.

My setup:

AMD XP 2700
1GB RAM
120GB WDC HD
ATI Radeon 9200 SE graphics card with VGA+DVI out, running dual-head at
a combined resolution of 2704x1050
Hauppauge WinTV PVR 150 PAL retail
Fedora Core 5, updated with all RPMS from Redhat, freshrpms and atrpms
repositories
Kernel 2.6.16-1.2133_FC5.i686
mythtv-suite 0.19-59.at
ivtv 0.6.2


Suggestions anyone?

Thanks in advance,
David


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