[Libav-user] Seeking, timestamps, AVFrame, AVStream

[cyril apan]

>Okay, that's helpful. But then how and where and by what program is 

>timebase calculated?  Do the ffmpeg tools calculate it?  I don't see 
>how they can. 
 They'd have to look at every frame in the video and
>that could take a very long time.

You should know that video formats reserve some space for metadata. And a portion is dedicated to describe track properties like VBR/CBR, total time length and so on.
FFmpeg relies on those metadata to initiate everything but then can recompute some on the fly, some other tools allows to actually calculate those track metrics directly from track content, it's safer but slower of course.

Cheers,

Cyril APAN.
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