Fixing inconsistent A/V desync in old video

[Ygramul]

Source video

Direct download

I know the quality is absolute garbage, but I'm a fan of that bassist, so please help me out.

The synchronisation is all over the place and I don't know what to do about it. The video is at variable ~15 fps and simply adjusting audio delay in MPC-BE doesn't do anything. I'm not sure if the fact that a frame freezes for the last 5 seconds makes the issure worse, so please skip to the end to see for yourself.

I tried resampling FPS in Avidemux (codec: x264 -> Filters -> Transform -> Resample FPS -> Mode: 29,97; Interpolation: Blend). Still can't sync the two tracks.

[LigH.de]

There are some filters in video scripting engines like Avisynth or VapourSynth like source filters which force sync to a fixed frame rate while reading the video stream from the source (e.g. DirectShowSource or FFMS2 with fps related parameters) while keeping a constant speed reading the audio stream (Avisynth: EnsureVBRMP3Sync()). But still, there is no guarantee that it helps in an automatic workflow. Some sources cannot be fixed automatically anymore because YouTube already has processed them in a way that "cements" the mistakes.

[Sharc]

In Avisynth you may try timestretch for the audio, something like

v=LWLibavVideoSource("Emeth.mp4",fpsnum=25000,fpsden=1000).trim(0,4380) #make 25fps CFR by inserting (repeating) frames
a=LWLibavAudioSource("Emeth.mp4")
s=timestretch(a,tempo=102) #adjust the tempo in %
Audiodub(s,v)

https://avisynthplus.readthedocs.io/en/latest/avisynthdoc/corefilters/timestretch.html

Or you can do similar in the timeline of an NLE.

[ProWo]

The source video is also asynchronous.
It is very difficult to find sync points for this video.
The videostream is still image only after frame 2699.