posting the following as there are some knowledgeable people around here. I want to remux the video from one source with the audio from another (same film, one disc has better audio, the other has better video).
The preferred video source has less blank screen run-in time than the video in the file with the preferred audio source. In other words, a plain remux results in a file with very delayed audio. I’ve had a look at I-frame thumbnails to give me a sense of how much delay I should put on the video track in mkvtoolnixgui, but I haven’t pinned down the delay exactly yet, and it occurs to me it should be possible to do so if I can identify the exact difference between the sources in time of audio start.
I’ve been round the block a few times with copilot trying variations of ffmpeg and ffprobe commands, without success.
Grateful for any suggestions.
Not sure what the best tool would be for this - you might need to cut audio in to separate files for each break
on further examination, I see that my sources are running at different video framerates. I was pleased to track down an Italian DV release of John Wick 2 (JW 1 in DV likely to arrive later this week). Curiously, the DV release clocks at 24.0 fps, whereas my UK HDR10-only release is the usual 23.976 fps. ffprobe is showing a difference in run-time that is consistent with speed up from 23.976 to 24.0, so I might need to reset the video framerate to 23.976 via mkvtoolnixgui to have any chance of syncing the TrueHD Atmos track from the UK release as an alternative to the DTS-HD 5.1 that comes with the DV version.
in case helpful for anyone looking for a solution, the amazing Dovi_Scripts package by RESET_9999 on the makemkv forum has some utility functions of likely interest to anyone who remuxes mkv’s. The 9-1 workflow gave me what I needed, auto detection of the likely time difference in the first frame.