I am quite new in the area of audio/video manipulation so apologies if the question is obvious. I did not manage to find an answer online, though.
I have a MKV file with several tracks: video (MPEG4), audio (DTS EN), audio (AC3 FR) and subtitles. I wanted to extract the video and French audio, then merge them back into an MKV file. I did this via mkvextract and mkvmerge (without any specific options). The MKV file I got is playable but the audio is shifted (by 10 or so seconds). The audio in the original file is fine for both languages (ie. it is correctly synchronized with the picture).
I guess that there should be a way to align the video and audio, though I do not really understand why they are shifted since I did not do any manipulations on the extracted files.
I would be grateful for any hints. Thank you