Losslessly convert folder of MKV files from OBS to MP4 files

readme.md

OBS and other tools produce video files that are h.264 video and AAC audio in an MKV container. This is useful for a lot of tools, but there are also a lot of things that only work with an MP4 container.

This script will convert a folder of MKV files to MP4 files without doing any transcoding, which makes this LOSSLESS (and quite fast). It also is smart enough not to repeat a conversion that's already complete, meaning you can run it after adding more MKV files and it will not perform rework.

Requirements

• zsh (default on macOS, common on Linux)
• ffmpeg - tested with brew install ffmpeg version on macOS

Tested on macOS, but should work on any *nix with above requirements.

mkv2mp4.zsh

#!env zsh
## if `env` is not in your path, change the above to point to 
##   the absolute path of `env` on your system; often `/usr/bin/env`
for mkv in *.mkv ; do
    mp4="${mkv%.mkv}.mp4"
    echo -n "'$mkv' => '$mp4'"
    if [[ -f "$mp4" ]]; then
        echo " [SKIPPED] (MP4 already exists)"
        continue
    fi
    bytes=$(stat "$mkv" | cut -d ' ' -f 8)
    printf " (%.1fMiB)" $(( $bytes / 1048576 ))
    if (ffmpeg -i "$mkv" -codec copy -loglevel error "$mp4"); then
        printf " [OK]\n"
        ## Uncomment the line below if you want to remove the original MKV file after successful conversion
        # rm "$mkv"
    else
        printf "\nWARNING: exit code $? while encoding '$mkv', check for errors above\n"
        rm "$mp4" 
        continue
    fi
done