There are some mkv files i'm getting now whre the audio is in sync in the beginning and gradually goes out of sync towards the end. At the end it's about -100 to -150 off.

As I'm using mkvmerge GUI to remux these files, I wonder how can I stretch it there. In "Format Specifications" you can alter delay and stretch, but I don't know how to use the later.

Can anyone tell me how?

Thanks!