How to edit video without transcoding?

Question

Video

When transcoding a video, the quality of the image usually suffers greatly, or the size increases greatly.
I would like to do only primitive operations: crop, modification of audio tracks.
How to edit video without transcoding?
Or how to reduce quality loss at the same size?

Answer 1

For the case when the video does not change, the changes concern only the sound - you can use ffmpeg with encoding in the copy mode:
Video in this mode will not be compressed.
The same applies to primitive assembly.
With crop, the situation is worse - it will not be possible to do without transcoding, because for crop you need to restore full frames.