avi-->mpeg audio/video sync problems

[Mike**Rodgers]

Hiya,
I am emailing looking for some help with audio/video sync issues.

I am converting avi--->DVD(either ffmpeg/mencoder). I use the ffmpegx/sizzle
combo to create dvds, so I am only interested in the converted .mpg file.

Converting ntsc files works brilliantly, but recently I have been trying to convert
PAL files and the sync is completely out of whack, with the audio 2/3secs ahead of the video.
I have tried encoding to PAL and NTSC, just to check if the file was showing an error, but no matter how I convert, its always out of sync.

According to ffmpegx and VLC player the file definately is PAL and 25fps.

Do you know what could be causing the sync problems, or have any suggestions about what I could do to fix it?

Thanks in advance for your help,

Mike.

[major]

Difficult to say, I should need to look the process output (blue "i" icon in the Progress window) and/or to test with your file, in order to help.

[Mike**Rodgers]

Ello major, thanks for replying, below is what comes out in the diagnostics window. I took out the pgcs encoding data to save space!!:
-----------------------------------
Encoding started on Mon Nov 13 23:20:09 GMT 2006
FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
Mac OSX universal build for ffmpegX
libavutil version: 49.0.0
libavcodec version: 51.9.0
libavformat version: 50.4.0
Input #0, avi, from '/Users/mikerodgers/Desktop/The Departed.avi':
Duration: 02:20:11.5, start: 0.000000, bitrate: 679 kb/s
Stream #0.0, 25.00 fps(r): Video: mpeg4, yuv420p, 640x272
Stream #0.1: Audio: mp3, 24000 Hz, stereo, 56 kb/s
Output #0, dvd, to '/Users/mikerodgers/Desktop/The Departed.avi.ff.mpg':
Stream #0.0, 25.00 fps(c): Video: mpeg2video, yuv420p, 720x576, q=2-20, 4000 kb/s
Stream #0.1: Audio: ac3, 48000 Hz, 5:1, 448 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
bench: utime=8525.654s
video:2878240kB audio:459862kB global headers:0kB muxing overhead 2.849949%
STAT: Picking VTS 01
STAT: Processing /Users/mikerodgers/Desktop/The Departed.avi.ff.mpg...
STAT: VOBU 16 at 1MB, 1 PGCS
----
STAT: VOBU 16976 at 3351MB, 1 PGCS
INFO: Video pts = 0.500 .. 8412.060
INFO: Audio[0] pts = 0.500 .. 8409.396
STAT: VOBU 16986 at 3352MB, 1 PGCS
INFO: Generating VTS with the following video attributes:
INFO: MPEG version: mpeg2
INFO: TV standard: pal
INFO: Aspect ratio: 4:3
INFO: Resolution: 720x576
INFO: Audio ch 0 format: ac3/6ch, 48khz drc
STAT: fixing VOBU at 1MB (17/16986, 0%)
-----
STAT: fixing VOBU at 3351MB (16977/16986, 99%)
STAT: fixed 16986 VOBUS
INFO: Scanning /Users/mikerodgers/Desktop/The Departed.avi.ff.mpg.DVD/VIDEO_TS/VTS_01_0.IFO
Encoding completed on Tue Nov 14 03:04:30 GMT 2006
-----------------------------

Hope this helps,
Mike.

[Mike**Rodgers]

*bump*

[major]

Possibly it is because the sound source has a sampling of 24000Hz. Try using mp2 sound in the DVD instead of AC3 to see if it makes any difference. Otherwise, you should convert the sound separately in some way and try to mux back with the .m2v video stream.

[tomlee59]

If you still don't get good sync, even after trying Major's suggestion, you might want to consider using Audacity (or similar audio processing tool; Audacity works great for me, and it's freeware) to adjust the duration of the audio track to match that of the video. Use the Adjust Tempo tool in the Effects menu. Lengthen or shorten the duration as needed to get things in sync (use VLC to get a precise value for the sync error at the beginning and end). Output as wav, then use ffmpegX to transcode into MPG audio. Audacity will help only if the rate of sync drift is constant (ie, the time difference grows linearly with time). That, plus the fixed offset correction you can apply in ffmpegX's muxing tool, usually gives you enough degrees of freedom to get the job done.

I get poor sync much more often than good (particularly from error-filled vidcaps, such as from VHS tape). Audacity has kept me from going (more) insane many a time. Good luck!