[vigneshv_psg]

i understand that this is the fastest way to extract frames, but it is limited by key frame availability in the original file (i.e.) you can only start the output from a keyframe.

in this case, it is important to be aware that the times you specify may not be extracted exactly. it will be off by a few frames based on keyframe availability. the only way to extract exact frames is to re-encode. :)

[nickjj]

This is true. Do you have a use case where being off by a few frames might be a deal breaker?

Personally I've created dozens of clips using this method and it always turns out ok. It gives you about ~1 second precision on where you want to make your cuts. After I create the clips I can play things back normally, complete with an ability to seek to specific points successfully.

[angrais]

>> Do you have a use case where being off by a few frames might be a deal breaker?

Yes, in action recognition tasks (machine learning), e.g., if you have a large video with temporal annotations (start/end times where an action occurs) you may want to extract clips to sense-check the annotations. Being exact is important.

[vigneshv_psg]

yeah it probably doesn't matter in practice. you may run into some audio sync issues.

but the ~1 second precision that you see is by accident where the source file happens to have a keyframe every 1 second. that may not be the case always. :)

[scottlamb]

Fundamentally (ignoring ffmpeg incantations), I think there are four options:

1. re-encode the whole thing

2. re-encode just the first GOP

3. start a bit early or late

4. include the full first GOP but use an edit list to instruct the player to skip to the timestamp of interest

[vigneshv_psg]

yeah these are pretty much the options. i believe the ffmpeg command that OP suggested would do option 3.