[umaar]

I battled with this a lot with https://github.com/umaar/video-everyday and still haven't found a better solution.

What I don't understand is, how can professional video editing tools trim accurately (and very quickly)? What are they doing differently to ffmpeg?

If do things the "fast way" with ffmpeg, the exported video has random black frames which I think is related to the keyframe issue you mention. If I do things the "slow way" (e.g. accurately) with ffmpeg, it takes a huge amount of time (at least with large 4k videos). But I don't understand how I can drop that same 4k video into Screenflow, trim 1 second out of it and export it in a matter of seconds.

[chenxiaolong]

All of the proprietary tools I know of for doing frame-perfect cuts (VideoRedo, TMPGEnc, SolveigMM) work by determining (guessing?) the original encoding parameters and then only reencoding the first and last GOP. The rest of the video is just remuxed.

[alternatetwo]

x264 encoded streams have the original encoding parameters included by default.

[fireattack]

Encoding settings metatag can be striped.

Regardless, I don't think these software are "matching" anything. TMPGEnc for example has settings to choose what quality you want for these re-encoded frames.

[_Gyan_]

The parameters being matched would be those that maintain decoder config. Usually, bitrate/quantizer values don't come into that.

[fireattack]

Oh yeah, the level would (should) definitely be kept.