MKV files are a container format for Video, Audio, Subtitles, and other content. The ScreenPlay Pro HD knows how to unpackage these files. But when most people talk about MKV files, they are referring to ones that contain H.264 encoded high definition media files.

The ScreenPlay Pro HD does not natively support H.264 encoded MKV files. In order to view these, you need to place them on your PC in a shared network directory and run the transcode server that comes with the install CD. However, unless you have a very high powered PC, the transcoding will be slow and will cause buffer delays while watching the video until the transcoding is completed. It is not a good solution, and due to the hardware used inside the player, is not likely to ever support H.264 natively.

Iomega support recommended to re-encode the video stream to a format that is natively supported by the ScreenPlay Pro HD.

Manufacturer Response:

The ScreenPlay Pro supports the following video codecs: MPEG-1, MPEG-2 (HL/ML), .MPEG-4 (part 2), ASP, DivX (3.11, 4.x, 5.x, 6.x, HD), Xvid, MP4. AVI, MOV, MKV, VOB, and ISO are container formats. Specifically, AVI, MOV and MKV contain file playback information as well as the formats used for audio and video streams. Because the H.264 codec is not natively supported. It is required to use the included transcoding server software to stream the video into a format that the ScreenPlay Pro HD can natively play back. Our recommendation, in this specific situation, would be to re-encode the video stream of the file into a format that is natively supported by the ScreenPlay Pro HD. This will make sure that the file can be played directly from the device without needing to be connected to a network.
High Definition MKV files DivX HD does work on the player and can be packaged in the MKV format and played natively from the player.

Actually, no matter what the Manufacturer says, mkv files mostly do not play, as well as mp4 files. To clarify: the same mkv file that did not play when remuxed to avi plays perfectly (therefore not a matter of codec, nor a matter of compressed headers because they were not compressed in the mkv file). mp4 files mostly do not play, although they should (h263+aac)?!

Besides that, old avi files made with divX 3.11 do not play as well...

While looking promising, and basically a decent product for its time, this player is one of the less liked, while Iomega is among the most hated manufacturers :( Sadly so.

Subtitles and Chapters Using AutoGK, I created an XVid video from a VOB source. Then I created the subtitle .SRT file. Using AVI-Mux, I created an MKV file from the XVid plus the .SRT file. I manually added my own chapters. The subtitles appeared when I pressed the subtitle button on the remote. The chapters also worked, but not in the way I expected them to. I expected to be able to press the >>| button to go to the next chapter. Instead, it went to the next file in the directory. However, pressing the Goto button brought up an index and I could then select a chapter to play. This was with the MKV on the device, not transcoding it through PC.