Trying to change .mkv profile without re-encoding

[maldon]

I’m looking for any good software to change for example:

High@L3.1 to High@L4.1
High@L5.1 to High@L4.1

I don’t want to re-encode but I hope not to get a broken .mkv full of errors.

[LoRd_MuldeR]

You are probably talking about H.264 profiles (and levels) here. Even though H.264 streams can be stored in an MKV container, this has nothing to with the MKV container per se!

Anyway, the H.264 profile and level that is stored in the stream header is just a meta information. It indicates to the playback software (decoder) to which H.264 profile and level the particular H.264 stream complies to. That's it.

Even though, technically, it may be possible to change the H.264 profile or level that is stored in the header, this wouldn't "magically" change the properties of the actual stream!

For example: If your original H.264 stream is labeled with "High@L5.1", then that is probably for a reason. It means that this stream complies to H.264 profile "high", but not to the "main" or "baseline" profile; and it means that this stream complies to H.264 level "5.1", but not to any lower level – assuming that the H.264 encoder, which was used to create the stream, has emitted the correct meta information.

Consequently, if you only change the meta information in the header, but do not actually re-encode the stream, then you are pretending that the stream is compatible to a profile and/or level that, in fact, this stream is not compatible to!

So, not a good idea, probably

[maldon]

Ok, thanks a lot, LoRd_MuldeR. Then, I won't use H264LevelEditor.

[Asmodian]

There are devices that will reject streams correctly labeled High@L5.1 but then play the same stream perfectly if lied to. I believe this is usually when the device does not have enough bandwidth to decode High@L5.1 at max rates and the file uses other features that requires 5.1 but is well below the max bitrate for level 5.1.

If you can test on the device you are trying to fool editing the metadata can work well but it is risky. One file can be fine and another not, it depends on if the stream actually uses whatever aspect of the level the decoder cannot handle. If you actually want to change the video then, as MuldeR explained, editing the file to lie about what is in it is pointless.

Changing 3.1 to 4.1 will (almost) always work, of course I don't know why you would want to since anything that can play level 4.1 should also accept 3.1?