[mythtv-users] mythtv audio stuttering on 720p material after upgrade to Fedora 9

[Don Lewis]

Yesterday I upgraded my myth box from 0.21 and Fedora 7 to the latest
0.21+fixes and Fedora 9 using the rpms from atrpms.net.  My hardware is
an Athlon 64 X2 4000+ on an Abit AN-M2HD motherboard with 1GB of RAM.
I'm using the onboard GeForce 7050 graphics and driving my TV in 720P
mode through HDMI output.  Sound output is via the motherboard S/PDIF
output.  The video driver is the latest from Nvidia.  I'm using ffmpeg +
XVideo.  I've got UseEvents set to "true" in xorg.conf.

Before the upgrade, the only playback problem that I had was occasional
tearing that was mostly visible during horizontal pans, probably because
I haven't been able to enable OpenGL vertical sync.

Almost everything works fine since the upgrade.  The exception is
playback of previously recorded 720P material.  SD material works fine,
as does 1080i material, as long as I don't use an overly expensive
deinterlace mode.

When I try to play a recording that was broadcast in 720P, the audio
stutters every few seconds and the video seems to alternate between
running at full speed and at about half speed with the same rhythm as
the audio problems.  When the audio drops out, my receiver shows that
the digital audio signal has has been lost.  The problem is much worse
if I disable the extra audio buffering.  Then I only get brief snippets
of sound, and the video appears to be running slow all the time. I've
tried twiddling a bunch of the playback knobs and nothing seems to help.
CPU usage is low, maybe 30%,, and the problem still occurs even if I set
deinterlacing to none.  I can play the same recording using mplayer and
it works just fine.  The log file shuws a bunch of buffer underruns:

2008-09-15 13:07:06.570 [mpeg2video @ 0x52089a0]ac-tex damaged at 7 3
2008-09-15 13:07:06.575 [mpeg2video @ 0x52089a0]Warning MVs not available
2008-09-15 13:07:06.894 TV: Attempting to change from None to WatchingPreRecorded
2008-09-15 13:07:06.899 DPMS Deactivated
2008-09-15 13:07:07.107 AFD: Opened codec 0x8a831c0, id(MPEG2VIDEO) type(Video)
2008-09-15 13:07:07.108 AFD: codec AC3 has 2 channels
2008-09-15 13:07:07.108 AFD: Opened codec 0x8ab2dc0, id(AC3) type(Audio)
2008-09-15 13:07:07.206 [mpeg2video @ 0x52089a0]ac-tex damaged at 7 3
2008-09-15 13:07:07.213 [mpeg2video @ 0x52089a0]Warning MVs not available
2008-09-15 13:07:07.246 [mpeg2video @ 0x52089a0]ac-tex damaged at 7 3
2008-09-15 13:07:07.254 [mpeg2video @ 0x52089a0]Warning MVs not available
2008-09-15 13:07:07.414 AFD: Opened codec 0x8c3fd60, id(MPEG2VIDEO) type(Video)
2008-09-15 13:07:07.415 AFD: codec AC3 has 2 channels
2008-09-15 13:07:07.415 AFD: Opened codec 0x8c17150, id(AC3) type(Audio)
2008-09-15 13:07:07.420 Opening audio device 'spdif'. ch 2(2) sr 48000
2008-09-15 13:07:07.420 Opening ALSA audio device 'iec958:{ AES0 0x02 }'.
2008-09-15 13:07:07.572 Opening audio device 'spdif'. ch 2(2) sr 48000
2008-09-15 13:07:07.572 Opening ALSA audio device 'iec958:{ AES0 0x02 }'.
2008-09-15 13:07:08.693 VideoOutputXv: XVideo Adaptor Name: 'NV17 Video Texture'
2008-09-15 13:07:08.771 OSD Theme Dimensions W: 640 H: 480
2008-09-15 13:07:09.715 TV: Changing from None to WatchingPreRecorded
2008-09-15 13:07:09.718 Realtime priority would require SUID as root.
2008-09-15 13:07:09.721 [mpeg2video @ 0x52089a0]ac-tex damaged at 7 3
2008-09-15 13:07:09.725 [mpeg2video @ 0x52089a0]Warning MVs not available
2008-09-15 13:07:09.819 OpenGLVideoSync()
2008-09-15 13:07:09.851 Video timing method: SGI OpenGL
2008-09-15 13:07:11.455 WriteAudio: buffer underrun
2008-09-15 13:07:11.465 WriteAudio: buffer underrun
2008-09-15 13:07:11.467 WriteAudio: buffer underrun
2008-09-15 13:07:11.471 WriteAudio: buffer underrun
2008-09-15 13:07:11.473 WriteAudio: buffer underrun
2008-09-15 13:07:11.521 NVP: prebuffering pause
2008-09-15 13:07:12.073 WriteAudio: buffer underrun
2008-09-15 13:07:12.081 WriteAudio: buffer underrun
2008-09-15 13:07:12.083 WriteAudio: buffer underrun
2008-09-15 13:07:12.087 WriteAudio: buffer underrun
2008-09-15 13:07:12.091 WriteAudio: buffer underrun
2008-09-15 13:07:12.138 NVP: prebuffering pause
2008-09-15 13:07:12.204 WriteAudio: buffer underrun
2008-09-15 13:07:13.977 WriteAudio: buffer underrun
2008-09-15 13:07:15.245 WriteAudio: buffer underrun
2008-09-15 13:07:15.253 WriteAudio: buffer underrun
2008-09-15 13:07:15.255 WriteAudio: buffer underrun
2008-09-15 13:07:16.146 WriteAudio: buffer underrun
2008-09-15 13:07:16.154 WriteAudio: buffer underrun
[ snip ]