Hi,
Trying to isolate the source of a 'sync' problem, I tried re-importing
my rendered project back into Cinelerra, and founc significant timing
changes. This is distressing, and I don't know what to make of it or
how to fix it.
Here are my steps:
1. Render the multi-track project (say, 'project.xml ') in Cinelerra, in
the 'documented' way:
audio to 'project.ac3' (448 kbps)
video to 'project.m2v' (piped to ' ffmpeg -f yuv4mpegpipe -i - -y
-target ntsc-dvd -f mpeg2video %')
2. Mux in ffmpeg:
$ffmpeg -i project.ac3 -i project.m2v -target ntsc-dvd project.mpg
Upon viewing 'project.mpg', I find noticeable loss of sync between sound
and picture.
3. So, I imported my rendered files back into the Cinelerra project on
new tracks as...
(V1) project.m2v
(V2) project.mpg
(A1) project.ac3
(A2) project.mpg
and compared the timing of these tracks to the edits in the original
audio & video tracks.
4. I find that the audio-only track (.ac3) appears 'perfectly' in-sync,
but ALL the video versions are shifted with respect to the original
edits.
In the worst case, at 3 minutes on the timeline, 'project.m2v' seems to
have dropped more than 2 seconds (60 frames). Surprisingly, the .mpg
file -- which was made FROM the .m2v -- has 'only' dropped about 10
frames. By the end of this 13-minute project, the .m2v has lost 3
seconds of video and the .mpg is off by about 10-15 frames.
So, it looks as if - even when I've carefully fixed sync in Cinelerra -
my final .mpg is likely not to be in sync.
Any suggestions on what I should do differently?
Thanks!
For what it's worth, my Cinelerra is ....
Cinelerra 2.1CV
Build date: Sat Mar 28 08:14:39 EDT 2009
Quicktime version 2.2.0 (Internal ffmpeg)
Libmpeg3 version 1.7.0
