[FFmpeg-user] What does ffmpeg do when packs switch?

Carl Eugen Hoyos ceffmpeg at gmail.com
Thu Feb 6 17:05:47 EET 2020

> Am 06.02.2020 um 13:14 schrieb Mark Filipak <markfilipak.windows+ffmpeg at gmail.com>:
> What does ffmpeg do when packs switch from hard-telecine to soft-telecine right in the middle of a GOP?

It doesn’t “do” anything because it doesn’t know the concepts of hard- and soft-telecine.
It doesn’t “just” take what the decoders output, it assigns proper timestamps to the frames (as it does with all frames coming out of a decoder). If the input was soft-telecined, FFmpeg only sees progressive content, often 24000/1001 frames. Hard-telecined means 30000/1001 frames, the telecine effect can be undone if done properly.
If the input contains both soft- and hard-teleconference content, FFmpeg sees variable framerate input (which it actually is).

Carl Eugen

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