Audio Commentary Sync Problem

[Randy801]

Hi Everyone, help please!

Over the months, I have been slowly converting my media library to MKV format, painstakingly ripping, muxing and merging. I'm familiar with mkvmerge and use it frequently to edit audio, subtitle tracks delay, etc.

Today I ran into an issue and after hours of trying to figure it out, I'm at my wit's end.

I have a 1080p MKV movie file (23.976fps) and a 480p MKV movie file (29.970fps), the latter contains 2 x audio commentary tracks which I am trying to merge into the former 1080p MKV. I can merge fine, but the audio of the commentaries don't sync with the video.

When I timestamp delay the audio I can get it perfect for the first few minutes, but by the end of the film it's out of sync again.

I assumed it was from the fps being different. But wouldn't that affect the video only? Not the audio?

Any specs or files that would be helpful to you I will gladly submit. It's driving me crazy.

[KarMa]

Older PAL versions of movies will often be 25fps, which is done by speeding up the movie and the audio from 24fps to 25fps. For NTSC movies they are often just slowed slightly to 23.976fps from 24fps. If you are mixing PAL and NTSC audio or video you are going to get this problem.

[Randy801]

Hi, I don't think it's a PAL / NTSC thing? The movie is American, from 1996, my 480p DVD is a Region 1.

[aedipuss]

the source of the 1080p version may be different than your dvd. as in a different version/cut.

[KarMa]

Ok, I didn't see you listed the frame.rates until now.

"I have a 1080p MKV movie file (23.976fps) and a 480p MKV movie file (29.970fps)"

Yeah those should be just NTSC framerates. The 29.970 version should just have an extra frame for ever 4 frames on the 23.976 version. A 4:5 ratio (23.976/29.970). With that extra frame usually being a duplicate or telecined frame of the normal 4 frames. The audio should be interchangable between the two. Does the commentary work fine on the 480p version?

[Randy801]

Yes, the 480p MKV is a direct rip from my original DVD using MakeMKV. It's bang on.

Good to know about the fps thing, I was going down that rabbit hole for nothing. That also explains why I've done this before and never had any issues.

Well, if it's not the FPS timing, I wonder if aedipuss is on to something and I need to watch this 1080p version VERY carefully and see if the slightest edit has been made. This will be painstaking, if so. The sync is only off by a few seconds, but enough to distract.

The movie is relatively unknown, but one of my faves. Night Falls on Manhattan (1996, Andy Garcia, Richard Dreyfuss, directed by Sidney Lumet). It's never been released on anything but Region 1 DVD and I doubt will ever make it to Bluray... thus my eagerness to get this right.