Convert Video to MKV Matroska

While MP4 and MKV can both hold H.264 and H.265 video, they differ significantly in capability:

• Audio tracks: MP4 supports limited multi-track audio; MKV supports unlimited tracks including DTS-HD, Dolby Atmos, and TrueHD.
• Subtitles: MP4 supports limited subtitle formats; MKV supports SRT, ASS, PGS, and many more simultaneously.
• Error recovery: MKV has superior error recovery — partial files can often still be played.
• Chapters: Both support chapters, but MKV's implementation is richer and more commonly used.

Plex and Kodi both natively support MKV with H.264 and H.265 for direct play — meaning the file streams to your TV or client without any server-side transcoding. Transcoding burns CPU, introduces lag, and downgrades quality. Keeping your library in MKV format avoids this entirely.

Plex recommends MKV with H.264 or H.265 and AAC or AC3 audio for the broadest client compatibility across Smart TVs, Rokus, and Fire Sticks.

If your MP4 already uses H.264 or H.265 video, converting to MKV can be done as a remux — the video data is moved to the MKV container without touching a single frame. This is lossless, instant, and the correct choice in nearly all cases.

Re-encoding is only needed when you want to change the codec (e.g., H.264 → H.265) or when the source audio uses a format incompatible with MKV (rare).

One of MKV's most valued features is soft-subtitle embedding — storing subtitle text inside the container so media players can toggle them on/off at will. SRT, ASS, and VTT subtitle tracks can all coexist inside a single MKV file.

This is a major advantage over MP4, which has limited support for embedded subtitles. For workflows requiring subtitle embedding alongside video conversion, MKV is the professional choice.

4K HDR video requires a container that can carry HDR metadata (HDR10, HDR10+, Dolby Vision) alongside the video stream. MKV fully supports all HDR formats, making it the standard container for 4K Blu-ray rips and HDR home theatre files.

For HDR content, always use MKV with H.265/HEVC — it's the only combination that preserves the full HDR colour grading and dynamic range intended by the filmmakers.