MKV to MP4
Repackage a Matroska MKV into MP4 with no decode and no re-encode. A subtitle or attachment track MP4 has no room for is dropped and named, the video and audio packets are copied across untouched.
MKV to MP4 moves a Matroska file into an MP4 wrapper by copying its video and audio packets straight across, nothing decoded. A subtitle or attachment stream MP4 cannot hold gets left out and named in the result rather than lost quietly. Node, the CLI, or MCP handle this exactly like a browser tab does.
Questions
Does everything in my MKV make it into the MP4?
The video and audio packets do, copied across with no decode. A subtitle track or file attachment MKV can carry has nowhere to go in the MP4 structure, so those are dropped and named in the result rather than discarded silently.
Is there any quality loss?
No, for the tracks that carry across. This is a packet copy, not a re-encode, so the video and audio are bit for bit what the MKV held, aside from any track MP4 cannot store.
Which engine handles this, and where can it run?
A packet-copy remux tool copies data through mediabunny with no decode step, so this runs in Node, on the command line and through MCP as well as the browser, unlike a WebCodecs-based transcode.
What size should I expect?
Close to the source MKV size, since the video and audio packets are unchanged; dropping a subtitle track or attachment can make the MP4 slightly smaller.
What is the reverse page?
There is none. Nothing on this site writes MKV.