[Libav-user] ffmpeg ; splitting an input movie into multiple tracks in a single output movie, possible?

"René J.V. Bertin" rjvbertin at gmail.com
Sat Dec 8 02:07:33 CET 2012

On Dec 08, 2012, at 00:06, Carl Eugen Hoyos wrote:
> My guess now is that you argue that for two given codecs (no 
> matter if mjpeg, mpeg-4 asp, mpeg2video, flv1 or snow), the 
> following command line always produces files of nearly identical 
> size:
> $ ffmpeg -i input -vcodec xxx out.avi

No, not always, but for the files I'm working with. When I compare

> ffmpeg -i 4000kbaud.m4v -vcodec copy out1.mov
> ffmpeg -i 4000kbaud.m4v -vcodec mpeg4 -b:v 4000k out2.mov
> ffmpeg -i 4000kbaud.m4v -vcodec mjpeg -b:v 1150k out3.mov

I get 3 output movies that are all at (approximately) 4000kbits/s, and all approximately the same size as the input.
You may not agree, but it my experience that material that has already been compressed with a lossy codec is often hard to compress further - and in this case the input already shows visible blocking artefacts. In fact, 720x576 @ 12Hz, that gives almost 5000k pixels/s, so if I'm not missing something the content is already compressed to less than a bit per pixel ... and I have no idea if that's stretching it or not, in fact.


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