Muxing, can't sync track

[Azubro]

Hello everybody, hope you can help me with this. This is my first time doing this so i will be very detailed and specific

What i have:

Movie1 (lenght 01:26:49)
video 24.00 fps - original frame rate 23.976 (24000/1001) don't really know what it means
track 1 ita 93.750 fps
track 2 jpn


Movie2 (lenght 01:26:47)
video 23.976 (24000/1001) fps
track 1 jpn 46.875 fps - delay relative to video 20ms



Movie1 is in sd, so i wanna extract both the audio tracks and put them in movie2 that's in hd. Problem is that no matter the delay i put in mkvtoolnix they are always out of sync. If the tracks are synced at the beginning towards the end the audio is late, viceversa if the end is synced the audio at the beginning come too soon. Any idea how to fix it?

[Bernix]

Because it has diferent lenght, change speed in Audacity, from movie 1 - 1:26:49 to movie 2 - 1:26:47. And then it should be o.k.

[Azubro]

So i need to speed up the tracks from movie1 right? Doesn't this compromise the fidelity of the sound making it faster than the original?

[Bernix]

very very minimal. you can use change tempo and it will not cause pitch change. The speed change will be hardly noticable. it is something like 0,9999 change

Bernix

[Azubro]

Wouldn't be better to simply cut two seconds from the track (choosing a spot with no sound)? Also i've found another problem, the tracks i wanna merge are DTS files so i'm not sure if i can edit them and audacity does not open them. Any advice?

[johns0]

Nope,since the files are different length they need to be speeded up or down,cutting out 2 seconds means it will got out of sync anyways.

[Bernix]

I have found software that can read/write DTS format. It is Ocean audio. But it cant speedup slowdown audio. You can here convert DTS f.e. to AC3, Flac or any other format, that Audacity understand. And then convert it back to DTS here. I know, it is weird way, but only one I can see.

If you install ffmpeg for Audacity, you can be able to import dts throught ffmpeg. I have not any dts file, so I cannot test it. But I try to export to dts without succes

You can download ffmpeg for audacity here http://lame.buanzo.org/

Then you can drag drop to audacity the DTS. And work with it. The problem is I didnt find how to export as DTS. So I exported it as AC3. And I hope I will be able to convert it in ocean audio back to DTS.
And I suggest you to read this https://shkspr.mobi/blog/2015/07/exporting-multitrack-surround-files-in-audacity/
Then you can recode AC3 to DTS in ocean audio with no problem. But I think is better to keep it in AC3. It is your choice.

Bernix

[Azubro]

Ok, now i'm really confused

I installed ffmpeg to audacity, imported track 1 (dts) of movie1 and changed the tempo from 5209.21 to 5205.40 seconds (the lenght of the track of movie2) with a percent change of 0.073 and exported as ac3, but when i mux it on movie2 now it seems even more out of sync than before. Any idea what i did wrong? The only weird thing i saw is that if i open again the track in audacity it says 5205.41 instead of 5205.40

[johns0]

The length of the audio doesn't always match the video length,you will need to adjust the audio in mpc-hc near the end to match the video sync,then take that adjust to calculate the needed time.

[Bernix]

and changed the tempo from 5209.21 to 5205.40 seconds

I thought that lenght of the second movie is about 5207.something... from your first post
Maybe little mistake

Bernix

[mazinz]

Just throwing it out there-- are you absolutely positive both films are exactly the same? Different formats usually mean different film transfers and it is very possible the HD source may have an extra 2 seconds somewhere that the (assuming older) SD version does not have

[johns0]

Also in scene changes sometimes one version has more delay and after a few scene changes then it will be very tough to match the sync.

[Azubro]

I'm still having problems


for example with -980ms in mphc the original dts track is in sync at the minutes 2.33(first dialogue) and 27.14 but way late at 55.05 and near the end at 1.16.19.

-2000ms to sync it at 1.16.19

so -2000+980 and i cut the result in change tempo

now the track is perfectly synced at 2.33 and 1.16.19 but way out of sync near the middle. At the minute 27.14 is half a second too soon and extremely late at minute 55.05

this is really weird

I made various adjustments changing the tempo by little perceantages but the track keeps being out of synch no matter what

[johns0]

It's not weird,as i already said there's good chance the audio track has different scene changing length than the other one so it wont match by stretching or shrinking the audio,you will have to go the each scene change and see how long it takes to get to a new scene,this can happen every 8 minutes,then you need to either cut or extend the scene changes as needed.