[FFmpeg-user] trouble with -vcodec copy
Arlo Leach
lists at arlomedia.com
Thu Nov 10 18:00:57 CET 2011
Hello,
> Could you upload a sample to http://www.datafilehost.com/ and post the download
> link here?
>
> You may have found a new feature that allows libavcodec not to output initial
> H264 frames that cannot be decoded (because the stream does not start at gop
> boundary), but that cannot be the problem you have seen with the old FFmpeg
> version.
I just put them on my site because one of the files is larger than 100 MB.
I also did some more tests and found that the ability to extract good a sample clip depends on the video source and is not affected by my first command that reformats the video.
1a) This is a video I encoded using Handbrake:
http://www.arlomedia.com/projects/ffmpeg/band.mp4
1b) This is the same clip reformatted with ffmpeg:
http://www.arlomedia.com/projects/ffmpeg/band_formatted.mp4
1c) And a shorter clip extracted from that (missing first six seconds):
http://www.arlomedia.com/projects/ffmpeg/band_formatted_sample.mp4
1d) However, I also lose some of the video if I extract from the original clip, so apparently my reformatting is not causing the problem:
http://www.arlomedia.com/projects/ffmpeg/band_sample.mp4
2a) As another test, this is a trailer downloaded from apple.com/trailers:
http://www.arlomedia.com/projects/ffmpeg/trailer.mov
2b) I can extract a sample clip from that with no problems:
http://www.arlomedia.com/projects/ffmpeg/trailer_sample.mp4
2c) Or reformat it and then extract a sample clip with no problems:
http://www.arlomedia.com/projects/ffmpeg/trailer_formatted_sample.mp4
So now the questions are, what is it about the first clip that causes some of its video to be lost when extracting a sample, and can I fix that when I reformat the original clip?
Thanks,
-Arlo
_______________________________
Arlo Leach
http://arlomedia.com
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