1- MKV does not work with many editors, as you know. MKV is a container, like a “folder” in very simple terms. Inside this “folder” is an h264 AVC video track most likely, which is very common, and fits in MP4s too, which DO work in editors. You need to either use ffmpeg to convert the mkv to mp4 (which will be quick and will not lose quality), or re-encode it while also switching the container (like using handbrake) but this will take longer and can slightly reduce quality.
Look up how to use ffmpeg on a mac, put your movie in the folder, and use this command
ffmpeg -i title.mkv -codec copy title.mp4
This will copy over everything into an mp4. BUT, the audio might not work, as you’ve said.
Regardless, you can still do the easy way with handbrake, just make sure to go to the audio tab and delete every audio channel except the one you want (usually the best quality one), set it to AC3 and make sure it’s all maxed out for quality etc
Or, here’s what I do without having to convert things and re-encode.
2- If we go back in time, before you do the mkv->mp4, we can work with it to extract the audio first. The audio is most likely DTS, or some other type used in blu-ray releases. You should convert to it to 24 bit 48kz wav so that you can work with it.
There’s a couple options. First off, it’d just be MUCH easier if you didnt need them attached. You can have the movie & audio tracks be seperate, you just load them in, and then make sure they both start at 00:00 and are lined up.
Youll want to find a program that will let you remove ALL the audio tracks except the main English 5.1 audio. If you load it into handbrake… it should show you them and you can X them all out, or you can use ffmpeg.
Im on windows, but my method is:
-Rip blu ray, I have mkv
-Remove all random audio tracks/subtitles using MKVToolNix (Idk if its on mac)
-Or, you can use MediaInfo (view->text) to see all audio tracks and see which ones you need to remove, and then use ffmpeg to remove audio tracks, youll need to google how
-I now have an mkv with 1 audio and 1 video
-I convert the mkv to mp4 using ffmpeg, so it can be loaded into programs, the audio can be lost here, idc
-Then I load that mkv into Audacity and it’ll automatically load in the 6 mono channels of audio and obviously ignore the video since its an audio program, I then export each as mono wavs, and then I set up 5.1 in my editing program manually
To do things perfectly, it’s gonna be a couple hour process, but I assure you everything can be done to get it work