2021-10-05, 07:05 PM
Let's first state a (not so) obvious fact: audio track from 29.97fps has the same speed of 23.976fps - that's because video has telecine.
Then; audio tracks from 24fps and 23.976fps have NOT the same speed! So, one should be slowed down, or the other should be speed up; which one is up to the user, but I'd always keep the lossy untouched - or slow down/speed up the lossless, that is the same; in case there are two (or more) lossless tracks, I'd go with 24fps to keep theatrical timing.
In any case you have tracks of only one out of two of this given speed, it's better to keep them as they are and change video fps - it will NOT re-encode video, but it's just a flag that says to the player which speed to play video.
So, answers to the questions:
1) first decide which speed the final project (audio+video+subs tracks) you want to get; then you have to change audio speed (if needed) BEFORE any edit; then you can cut/paste/delete/add anything
2) just select video fps in the muxer you use - like tsMuxeR or MKVtoolnix
3) is it possible to have 24fps and 23.976fps tracks of the same video, from different sources, at the same lenght - even if not very often; in that case, one has more (or the other has less) frames, hence audio of one track would be ahead/behind until it reaches the missing/added frames part, then will be behind/ahead. Or, simply, the tracks are a bit (or a lot) out of sync; you will notice it in particular during dialogue - different people hear different out of sync tracks, but usually it started to be noticed around 10/20ms, while is plain evident around 30/40ms for anyone; if it's just few ms, personally I'd not bother - unless you put it on sync at the beginning and it will stay put for the whole track, of course!
2)
Then; audio tracks from 24fps and 23.976fps have NOT the same speed! So, one should be slowed down, or the other should be speed up; which one is up to the user, but I'd always keep the lossy untouched - or slow down/speed up the lossless, that is the same; in case there are two (or more) lossless tracks, I'd go with 24fps to keep theatrical timing.
In any case you have tracks of only one out of two of this given speed, it's better to keep them as they are and change video fps - it will NOT re-encode video, but it's just a flag that says to the player which speed to play video.
So, answers to the questions:
1) first decide which speed the final project (audio+video+subs tracks) you want to get; then you have to change audio speed (if needed) BEFORE any edit; then you can cut/paste/delete/add anything
2) just select video fps in the muxer you use - like tsMuxeR or MKVtoolnix
3) is it possible to have 24fps and 23.976fps tracks of the same video, from different sources, at the same lenght - even if not very often; in that case, one has more (or the other has less) frames, hence audio of one track would be ahead/behind until it reaches the missing/added frames part, then will be behind/ahead. Or, simply, the tracks are a bit (or a lot) out of sync; you will notice it in particular during dialogue - different people hear different out of sync tracks, but usually it started to be noticed around 10/20ms, while is plain evident around 30/40ms for anyone; if it's just few ms, personally I'd not bother - unless you put it on sync at the beginning and it will stay put for the whole track, of course!
2)
