Cutting Video with MKVmerge?

[DanDare1983]

Hi,

Every once in a while I'll make a remux which has coloured bars or excess padding at the start or end of the movie which really annoys me so I was wondering if anyone could direct or point me to a step by step guide which could help me cut the coloured bars or padding away. I keep seeing cut to iframe etc but am still new to this but do know all the basics. Also I'm using the latest mkvmerge. Any help would be appreciated.

[Asmodian]

Cutting at specific frames and cutting at I frames are very different operations. With the current consumer video formats it is actually impossible to cut at a specific frame without losing quality, at least in a few frames near the cut.

Because frames are dependent on the previous frames, you need all the frames up to the last I frame in order to decode a later frame. This is why you sometimes see digital video go into that blocky smeary mess when the connection is poor. The decoder lost the I frame or a previous P frame and is decoding P or B frames without the original reference blocks.

This means frame accurate cutting of video requires decoding and re-encoding of the entire video or only those frames missing reference blocks, which is sometimes called "Smart Rendering".
How to cut video frame accurate without encoding? (https://forum.doom9.org/showthread.php?t=182026)

[hubblec4]

My opinion:

Never ever cut or join/append mkv's, because there is a Matroska design issue which often appears.

The best way is to use ordered chapters. Only with this method/feature you can virtually cut frame accurate!

[karbre]

Never ever cut or join/append mkv's, because there is a Matroska design issue which often appears.

Can you elaborate about this design issue? I often use MKVToolNix to cut at keyframes and never had a problem yet.

[hello_hello]

I'd be keen to know what the issue is too, as I use MKVToolNixGUI to cut and/or join MKVs regularly without any problem.

DanDare1983,
If you open an MKV with MPC-HC and navigate with the keyboard left and right arrow keys while holding down the shift key, you'll jump between keyframes.
When you're at the appropriate keyframe, use the Navigate/GoTo menu (CTRL+G) to get the frame number. Use it when cutting with MKVToolNix (split after frame number). Of course there's no guarantee there'll be a keyframe where you want to cut. Sometimes there is, sometimes not.