Changing playing speed of MKV file

[djdj]

For convenience, here mkv file means mkv without any audio or subtitle. (only video)

Is it possible to chainge the playing speed of the MKV file, only chainging just a few bytes of MKV header ?

I tried to change playing speed of MKV with many tools, and compared input.mkv and output.mkv.

In any case, input.mkv and output.mkv were globally different.... (the different spots were spreaded over whole file content when viewed in hex editor)

There is a helpful article, https://github.com/mbunkus/mkvtoolnix/wiki/Wrong-frame-rate-displayed

(I couldn't understand it perfectly..)

In short, my real question is
Q)Is it possible to chainge the playing speed of the MKV file, only chainging just a few bytes of MKV header ?

[Baldrick]

You can change the fps with mkvmergegui, open the mkv, select the video track, change the fps under format specific options. Start muxing. And it will play faster/slower.

[djdj]

Of course I tried with mkvmerge, and found input.mkv and output.mkv were globally different in hex editor.

You might think mkvmerge replaced only a few bytes, but it is NOT.

[djdj]

As you see, there are many different spots even in the middle of two files.

Note that there are abundant different spots especially in the end of file contents.

[Baldrick]

I guess the remuxing causes this. mkvpropedit can change some stuff directly on a mkv but not the fps.

[Cornucopia]

It shouldn't matter if the file has different ordering, packet grouping, etc., so long as the (VIDEO) file/stream does not get recompressed, and with mkvmerge it does not.

Scott

[El Heggunte]

For convenience, here mkv file means mkv without any audio or subtitle. (only video)

Is it possible to chainge the playing speed of the MKV file, only chainging just a few bytes of MKV header ?

Not possible. The playback of Matroska files uses frame timestamps.
When you change the video playback rate of an MKV file from (let's say) 25fps to 24fps,
you actually change all the timestamps for the video stream, not just "a few bytes" in the global header.

[djdj]

Thank you guys! I feel comfortable after knowing it is not possible!
Mastroka is very flexible but a little untidy.