[mythtv-users] A/V diverged by -3 frames

Christian Hack christianh at edmi.com.au
Mon Dec 27 12:10:54 UTC 2004


Using the libav option on mythfrontend (very recent CVS), I'm getting jerky
playback on one channel (SBS for the Australians) which seems related to
these error messages. It also seems that the pitch of the sound is off by
small fraction - slightly deeper. Using video as timebase results in exactly
the same result.

Note it mentions -3 frames and a frame rate of ~22fps.

Other channels work fine and only report the A/V diverged initially but sync
quickly and report 25fps from then on.

2004-12-27 21:50:03.829 Image size. imgx 0, imgy: 0, imgw: 720, imgh: 576
2004-12-27 21:50:03.829 positionMap[ 0 ] == 0.
2004-12-27 21:50:04.041 Position map filled from DB to: 45291
2004-12-27 21:50:04.042 SyncPositionMap prerecorded, from DB: 3829 entries
2004-12-27 21:50:04.042 detectInterlace(Ignore Scan, Interlaced Scan, 25,
576) ->Interlaced Scan
2004-12-27 21:50:04.042 Interlaced: Interlaced Scan  video_height: 576  fps:
-1
Input #0, mpeg, from
'/mnt/store/recorded/1028_20041227203000_20041227210000.nuv':
  Stream #0.0: Video: mpeg2video, 720x576, 25.00 fps
  Stream #0.1: Audio: mp2, 48000 Hz, stereo, 192 kb/s
2004-12-27 21:50:04.044 Position map found
2004-12-27 21:50:04.047 Opening audio device '/dev/dsp'.
2004-12-27 21:50:04.047 Opening OSS audio device '/dev/dsp'.
2004-12-27 21:50:04.055 Over/underscan. V: 0, H: 0, XOff: 0, YOff: 2
2004-12-27 21:50:04.060 Using XV port 103
2004-12-27 21:50:04.063 Image size. dispxoff 0, dispyoff: 96, dispwoff:
1024, disphoff: 576
2004-12-27 21:50:04.064 Image size. imgx 0, imgy: 0, imgw: 720, imgh: 576
2004-12-27 21:50:04.813 Realtime priority would require SUID as root.
2004-12-27 21:50:04.814 Changing from None to WatchingPreRecorded
2004-12-27 21:50:04.915 nVidiaVideoSync: VBlank ioctl did not work,
unimplemented in this driver?
2004-12-27 21:50:04.915 DRMVideoSync: Could not open device /dev/dri/card0,
Permission denied
2004-12-27 21:50:04.916 Using audio as timebase
2004-12-27 21:50:04.916 Video timing method: RTC
2004-12-27 21:50:04.916 Refresh rate: 16665, frame interval: 40000
2004-12-27 21:50:04.916 waiting for prebuffer...
...
2004-12-27 21:50:27.073 A/V diverged by -3.12928 frames, dropping frame to
keep audio in sync
2004-12-27 21:50:27.161 A/V diverged by -3.35083 frames, dropping frame to
keep audio in sync
'video_output' mean = '44006.10', std. dev. = '38828.64', fps = '22.72'
2004-12-27 21:50:27.164 A/V diverged by -3.0256 frames, dropping frame to
keep audio in sync

Using other channels I get the +3 frames and associated jerkiness _when_ I
select video as the timebase. Without using the video timebase option they
run as good as possible and report a pretty solid 25.0x fps.

2004-12-27 21:56:25.741 A/V diverged by 3.0109 frames, extending frame to
keep audio in sync
2004-12-27 21:56:26.228 positionMap[ 126 ] == 4320818.
2004-12-27 21:56:26.380 A/V diverged by 3.16602 frames, extending frame to
keep audio in sync
'video_output' mean = '43939.18', std. dev. = '12173.37', fps = '22.76'

Any ideas what's wrong? Could the latest libavcodec sync have buggered
things? This used to work before.



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