[mythtv-users] A/V Sync problem?
tom at compton.nu
Fri Dec 31 13:14:38 UTC 2004
I'm experiencing a number of strange timing related problems that
may or may not be related to audio and/or video sync issues. The
main symptom is that if a recording has been playing for a while
then hitting pause tends to cause it to jump back a way before
pausing. The longer it has been playing the further it seems to
A similar symptom occurs when fast forwarding - when returning to
play mode the video stream jumps back a way before returing to play
With verbose playback logging enabled the following messages appear
when starting to view a recording:
2004-12-31 08:59:06 Changing from None to WatchingPreRecorded
2004-12-31 08:59:06 nVidiaVideoSync: VBlank ioctl did not work, unimplemented in this driver?
2004-12-31 08:59:06 DRMVideoSync: Could not open device /dev/dri/card0, No such file or directory
2004-12-31 08:59:06 Using audio as timebase
2004-12-31 08:59:06 Video timing method: RTC
2004-12-31 08:59:06 Refresh rate: 40000, frame interval: 40000
That is then followed by a number of messages along these lines:
2004-12-31 08:59:06 A/V diverged by 4.71562 frames, extending frame to keep audio in sync
2004-12-31 08:59:07 A/V diverged by 6.1242 frames, extending frame to keep audio in sync
2004-12-31 08:59:07 A/V diverged by 6.93065 frames, extending frame to keep audio in sync
After some seconds those stop and we just get a stream of messages
'video_output' mean = '39995.01', std. dev. = '296.20', fps = '25.00'
avsync_delay: -30, avsync_avg: -29, warpfactor: 0.9, warpfactor_avg: 0.0178806
'video_output' mean = '39996.45', std. dev. = '266.68', fps = '25.00'
avsync_delay: -30, avsync_avg: -30, warpfactor: 0.9, warpfactor_avg: 0.023742
'video_output' mean = '39994.79', std. dev. = '273.46', fps = '25.00'
avsync_delay: -31, avsync_avg: -30, warpfactor: 0.9, warpfactor_avg: 0.0295645
Nothing special seems to appear when the recording is paused except
that the sequence restarts when playback is resumed.
Any suggestions as to how to resolve this, or where to look for more
clues as to the cause would be gratefully received.
Tom Hughes (tom at compton.nu)
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