Muxing with audio delays

[emmanu888]

I'm currently trying to insert the Canadian French audio track from the 3D Blu-Ray version of Coraline onto the MKV i made from my 4K copy because the 4K version has the European French audio track which i dislike.

However my problem now lies in, i put a 1980ms delay on the added audio track which syncs with the movie during the first 30 to 45 minutes of the movie.
Past 45 minutes i found out with VLC that i need to adjust the delay as the movie goes on so that it remains in sync.

What are my choices? Should i rip my 2D Blu-Ray copy of the movie and work with that audio track? I really want to have the 4K version of this movie in my Plex server with the dub that i grew up listening to.

Its definitely making me rage a bit that the delay i add is fine for the beginning of the movie but as it goes on i would have to delay the sound with a negative value as it keeps drifting and drifting out of sync.

I have the feeling this is due to how the 4K rip runs at 24FPS whereas the BD Rip runs at 23.976FPS and makes audio syncing a chore.

[ProWo]

Use clever FFmpeg-GUI.
Load your BD Rip (23.976fps), click main, click encode audiostream, select your audiostream (if there are several), click >>>.
Set the desired audio codec, set the "change length & pitch" settings like in the picture and click encode.
If done, you have your new soundtrack for the 4k movie.


[Attachment 74742 - Click to enlarge]

[emmanu888]

Use clever FFmpeg-GUI.
Load your BD Rip (23.976fps), click main, click encode audiostream, select your audiostream (if there are several), click >>>.
Set the desired audio codec, set the "change length & pitch" settings like in the picture and click encode.
If done, you have your new soundtrack for the 4k movie.


[Attachment 74742 - Click to enlarge]

I have to thank you so much! Doing that along with finding the proper delay synced up the French Canadian dub of the movie with the 4K version!

That was the missing piece of the puzzle! Modifying the audio track so that it lined up with the 24FPS of the 4K version and adding a delay to sync it!

[Ennio]

As another, opposite approach to your issue, you can instead change the framerate of your 24fps 4K video to run at same speed as the 23.976 audio. This can be done by rewriting timestamps of the videotrack. This handling doesn't take any recoding of audio or video. A proper audiodelay still has to be set though during muxing process.
I always rewrite video timestamps with a ffmpeg.exe commandline; undoubtedly ProWo can tell you whether this can be dictated by the GUI.

[ProWo]

I always rewrite video timestamps with a ffmpeg.exe commandline

Could you post an example of such a command line here?

[Ennio]

Sure, here's two I much use.

For rewriting 24fps timestamps:

ffmpeg -i input.hevc -c copy -bsf:v hevc_metadata=tick_rate=24:num_ticks_poc_diff_one=1 output.hevc

For rewriting 23.976fps timestamps:

ffmpeg -i input.hevc -c copy -bsf:v hevc_metadata=tick_rate=(24000/1001):num_ticks_poc_diff_one=1 output.hevc

FYI for Dolby Vision streams changing framerate has no bad influence on RPU. In-stream, the binaries are written as SEI messages. Speed doesn't matter.
When extracted, RPU data is written for (and can be edited using) framenumbers.

[ProWo]

Sure, here's two I much use.

For rewriting 24fps timestamps:

ffmpeg -i input.hevc -c copy -bsf:v hevc_metadata=tick_rate=24:num_ticks_poc_diff_one=1 output.hevc

For rewriting 23.976fps timestamps:

ffmpeg -i input.hevc -c copy -bsf:v hevc_metadata=tick_rate=(24000/1001):num_ticks_poc_diff_one=1 output.hevc

FYI for Dolby Vision streams changing framerate has no bad influence on RPU. In-stream, the binaries are written as SEI messages. Speed doesn't matter.
When extracted, RPU data is written for (and can be edited using) framenumbers.

Thx for your input.