How I would do it: ffmpeg -i input.mkv -vn -c:a libmp3lame -ar 48000 -ac 2 -b:a 192k output.mp3. If you want, you can crank the audio bitrate up to 320k to try to lose as little quality as possible, just know that it'll be almost double the size.
Hereβs how: Open the VLC media player and click Tools > Preferences. Click All at the bottom left corner. Click on the Input / Codecs tab, click Video codecs, and choose Demuxers > Matroska. Deselect Preload MKV files in the same directory on the right side, and click Save. Many video conversion tools, including VideoLAN VLC media player, HandBrake, and Wondershare Video Converter Pro, can convert MKV files to other video formats. For example, VLC can convert MKV videos to:.MP4 - MPEG-4 Video.WEBM - WebM Video.TS - Video Transport Stream.ASF - Advanced Systems Format X4cq.