[FFmpeg-user] Is there any good reason why FFmpeg doesn't do "-vcodec copy" automatically.

Phil Rhodes phil_rhodes at rocketmail.com
Sat Sep 30 23:38:09 EEST 2023

 > is there a good reason to throw a video file through ffmpeg when you> don't want to touch it?
I guess you might want to touch the audio but not the video, maybe?
In general, I suspect the reason it's not easy to implement the requested feature is that it isn't often trivial, or even possible, to know even quite roughly what settings were used to encode a video. As far as I know it'd be perfectly valid to have a video in certain codecs that might contain an enormous string of millions of I-frames, followed after hours, days or weeks with a single B-frame, and there wouldn't be any way to anticipate that other than just examining the whole file. You can't, as far as I know, know what the requested bitrate was when encoding the file. You can only know what the bitrate is. Different encoders use different techniques in different ways; there is no standard H.264 encoder, only a reference decoder, so there's not even a standard collection of settings to use as a basis.
As far as I know it's not actually possible to do what the OP seems to want to do, regardless.

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