[FFmpeg-user] fps in March 13 git: -r 29.97 = 2997 tbn ???

Mike Scheutzow mjs973 at optonline.net
Sat Apr 2 13:50:58 CEST 2011

sean darcy wrote:
> Converting to an android playable file, I can't seem to set the fps. 
> The input is 29.97. I tried setting -r to 29.97:
> ...
> Output #0, ipod, to 'OUTPUT1.m4v':
>   Metadata:
>     encoder         : Lavf52.102.0
>     Stream #0.0: Video: libx264, yuv420p, 720x480 [PAR 8:9 DAR 4:3], 
> q=0-69, pass 1, 10000 kb/s, 30k tbn, 29.97 tbc
> tbn is the framerate for the AVStream of the container, as I gather 
> from google. It seems that -r affects tbn of the output. But really 
> oddly.
> How do I set fps of the output?

You misunderstand the meaning of tbn. tbn is not the "framerate" of the 
container, it is the timebase.

A timebase is like a clock, and indicates ticks per second. Generally, 
higher values are better.

Both values of tbn you saw should work fine for your file. You got 
different values because 29.97 is not *exactly* equal to 30000/1001.

Also, be careful believing the tbn / tbc "Output #0" stats - they have 
been broken for months. Use 'ffmpeg -i infile' to get accurate values.

Mike Scheutzow

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