What you should know
MKV to MP4 makes a multi-track video compatible with living-room devices. MKV excels at archiving several languages and subtitles, but few TVs and hardware players can open it.
Conversion selects one video track, usually copying it if already H.264, and one audio track to convert to AAC. Other tracks and subtitles do not follow automatically.
Strengths
- Makes the video readable on TVs, consoles and set-top players
- The H.264 video track can be copied without re-encoding
- Lets you choose the language and drop useless tracks
- Reduces size by discarding duplicate audio
Limitations to know
- Unselected tracks are lost
- Subtitles do not always follow
- Audio almost always needs re-encoding (DTS, AC3 to AAC)
- An MKV with an exotic video codec requires a full re-encode
When to use it
Convert to watch on a TV, console or player that does not accept MKV, carefully choosing which audio track to keep. Keep the MKV for archiving with all its languages.
Quality, size and compatibility
If the video is H.264, track copying preserves quality exactly. Re-encoding audio to AAC is a negligible loss in practice, except for very demanding soundtracks.
Frequently asked questions
- Why does my MKV conversion lose languages?
- Because MP4 and most consumer players handle multiple tracks poorly. Conversion keeps one: choose the right one before starting.
- Is the video re-encoded?
- Not necessarily. If it is already H.264, it can be copied as-is into the MP4 container, which preserves quality and speeds up conversion.