Audio in sync in editing but not in remux

[Filippo]

Hello,
In Premiere I have a japanese audio + video tracks, I've added an english audio track and edited to match the JP length one, because the timings and fps of the two tracks are different. If I play the video in Premiere both audio are in sync with the video.
I export the english track in .AAC and in MKVToolnik I open the .mp4 JP video used in premiere and add the .AAC file.
I export the video. When playing, the audio starts at 0:00 as it should but there is about one second of black video, then it starts but the audio is no longer in sync. It's not that the first video frame are playing black, the video has a delayed start.
If I select the japanese audio track in VLC the audio is in sync and the video starts without delay.

I have set no delay option but I have no idea what could cause this.

[ProWo]

There is not enough information.
Open the muxed mkv file in clever FFmpeg-GUI, click main page, click multiplex.
Take a screenshot and post it here.

[Filippo]

There is not enough information.
Open the muxed mkv file in clever FFmpeg-GUI, click main page, click multiplex.
Take a screenshot and post it here.

Here's the screenshot, it's italian, not english, but still not in sync.


[Attachment 86758 - Click to enlarge]

[johns0]

Most likely the english version has different scene lengths when changing so it will be a big job getting it to match.

[Filippo]

Most likely the english version has different scene lengths when changing so it will be a big job getting it to match.

The problem is that they are in syc in Premiere, if I play the video the audio matches the scene as I have already changed the speed of every audio clip to match each scene duration. It's just the remux that does not.


[Attachment 86760 - Click to enlarge]

[davexnet]

Have you tried delaying (positive or negative) the audio in mkvtoolnix?

[ProWo]

Here's the screenshot, it's italian, not english, but still not in sync.

The Italian audio stream has a delay of -21ms,
just like the Japanese one. This is so little that it cannot be heard.
Is the Japanese stream synchronous?
If so, then the Italian stream is not correct.
What we need to know is the frame rate of the Japanese video and the frame rate of the video from which the Italian audio stream originates