Getting an MKV into Compressor

You drag an .mkv onto Compressor and nothing happens. No error, no unsupported-format dialog. The file simply will not add to the batch. Or it appears in a file browser grayed out, which is somehow worse, because it looks like it should work.

Compressor does not read Matroska. It never has. There is no preference to change and no plugin to install.

Why there is no plugin

This is worth stating clearly, because it is the top search result people are hoping for and it does not exist.

macOS 15 introduced Media Extensions, a framework that lets third parties add support for new container formats system-wide. That is genuinely the mechanism that could make Final Cut Pro and Compressor open MKV natively one day.

As of this writing there is no MKV Media Extension available, and Compressor still does not recognize the format. If that changes, the container problem goes away. The timing, audio, and channel-layout problems described across these pages will not, because none of them are caused by the container being MKV. They are caused by what a Matroska file can and cannot describe.

What the file actually needs

Nothing about your video. A Blu-ray or DVD backup is almost always H.264, HEVC, or MPEG-2, and Compressor has handled all three for years. The picture is fine. The box it arrived in is the problem.

Rewrapping into MOV takes the encoded video out and puts it into a container Compressor reads. No frame is decoded, nothing is re-compressed, and the job finishes about as fast as your disk can copy the file.

Why not just transcode it first?

You can. Run it through a transcoder, get a ProRes or H.264 file, and Compressor will take it happily.

You have also just re-encoded your source before handing it to the application whose entire job is encoding. Whatever Compressor produces is now two generations from the original instead of one. If you are making a delivery master, that is a real cost for a container change.

MOV, not MP4, for this

ClipReady writes either, but for a Compressor workflow choose MOV. It is what Compressor and Final Cut Pro expect, and if the picture inside is MPEG-2, as most film DVDs are, MOV is the only container ClipReady will offer, because MP4 can carry MPEG-2 but tools disagree about how.

What ClipReady does about it

Drop the MKV in and you get a MOV with:

• the video bitstream copied across exactly as it was;
• the frame timing repaired, so Compressor reads 23.976 rather than an averaged 23.81;
• audio Apple can decode, with the channel layout named so surround survives the trip;
• chapters and a real timecode track, neither of which an MKV can hand to Compressor.

Every track shows what will happen to it before the job runs, and the finished file is checked back through AVFoundation before it is saved.

Related

• ClipReady — the app this page describes
• Remux MKV to MP4 or MOV on a Mac
• ClipReady vs HandBrake