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

Carl Eugen Hoyos cehoyos at ag.or.at
Sat Dec 8 00:06:12 CET 2012

René J.V. Bertin <rjvbertin at ...> writes:

> >> What I mean is the size of the files I get on my sample videos.
> >> Guess I should have made that clearer. And of course I never 
> >> meant to say it depends on the framerate only, evidently it 
> >> depends on how much the images vary between frames.

("Guess" is probably the right word since it is not easy for me 
to understand above.)
Allow me to repeat:
mpeg-4 asp is (at least) one generation ahead of jpeg encoding, 
I strongly suspect it has advantages when encoding still images 
(although I don't know of any tests), the two encoders certainly 
cannot be compared for encoding of a real-world video stream (no 
matter the framerate) because mpeg-4 will always win a quality / 
size comparison by a large margin.
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 
$ ffmpeg -i input -vcodec xxx out.avi
This is certainly correct, the reason is that ffmpeg defaults 
to -vb 200k, so all codecs try to reach the same filesize 
(that may or may not be reached for given input etc.), the 
quality will vary significantly because the codecs do not 
have the same quality.
(The order is probably mjpeg->mpeg2video->flv1->mpeg4, with 
snow having great advantage for small bitrates.)

Carl Eugen

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