[FFmpeg-user] trouble with -vcodec copy

[Arlo Leach]

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