Prob with Avatar audio progressive out-of-sync

[JimmyBarnes]

At least I think it's progressive. Not noticeable in the first half of the movie, but certainly in the 2nd half where dialogue is not that common as it's mostly action. Very noticeable if you compare the same sections in the original m2ts.

Encoded 00002.m2ts to x264/MKV and muxed using mkvmerge with AC3 448 audio created using eac3to, latest versions of everything...

Done on a core2duo E8400 3+GHz PC with 4GB RAM.

Anyone had the same problem? (can't seem to Find)

[nm]

Sounds like the difference between 23.976 fps and 24000/1001 fps video framerates. If you use 23.976 fps instead of an exact rate, video will be 86 ms behind audio after an hour of playback and 173 ms after two hours. That's definitely noticeable.

[Groucho2004]

Sounds like the difference between 23.976 fps and 24000/1001 fps video framerates. If you use 23.976 fps instead of an exact rate, video will be 86 ms behind audio after an hour of playback and 173 ms after two hours. That's definitely noticeable.

Hm, my calculator thinks that the difference after 1 hour is 3.6 ms.

[nurbs]

It's 3.6 ms per hour. nm calculated how many frames per hour the difference is.

[nm]

Hm, my calculator thinks that the difference after 1 hour is 3.6 ms.

Ah, right, I missed a division by the rate. Should've used the units to see what comes out.

Beats me then. It's probably not the difference between 24 fps and 24000/1001 fps either because that would be noticeable pretty soon.

Edit: A single glitch somewhere in the source video or the audio stream may have caused the sync issue during encoding or muxing. That's more probable than a linear drift if the rates seem correct in the MKV.

[Lam3rD]

Hm, my calculator thinks that the difference after 1 hour is 3.6 ms.
My calculator says, that these are 3.6 seconds per hour (3600s/1001), which is quite a lot. I can notice the difference between 24 and 24/1.001 in the middle of of 3-4 min long video, so with a (3 hour) movie things would be beyond obvious. (around 10 seconds in the end)

[Groucho2004]

My calculator says, that these are 3.6 seconds per hour (3600s/1001), which is quite a lot. I can notice the difference between 24 and 24/1.001 in the middle of of 3-4 min long video, so with a (3 hour) movie things would be beyond obvious. (around 10 seconds in the end)

Well, your calculator works but your problem is that you don't read the posts you're replying to.

[JimmyBarnes]

Is there a util which can adjust framerate for MKVs like AVIfrate can do for AVIs?

[LoRd_MuldeR]

Is there a util which can adjust framerate for MKVs like AVIfrate can do for AVIs?

You can re-mux the MKV file with MKVMergeGUI from MKVToolnix and specify the desired frame-rate there...

[JimmyBarnes]

You can re-mux the MKV file with MKVMergeGUI from MKVToolnix and specify the desired frame-rate there...

OK, setting 23.975 (rather than the expected 23.976) restores AV sync throughout.

Why should this problem be, I have not had to make this sort of adjustment for any other BD?

Anyway to tell what the original M2TS framerate is?

:thanks:

[nm]

OK, setting 23.975 (rather than the expected 23.976) restores AV sync throughout.

Very strange, but a quick search on the net reveals that there are others that have had to do the same with Avatar Blu-ray.

Anyway to tell what the original M2TS framerate is?

I don't know a tool that could analyze all the timestamps easily, but what does FFmpeg say about the stream (ffmpeg -i video.m2ts)?