According to the manual for JVC’s first Blu-ray player to hit the United States, the XV-PB1 supports the  MKV multimedia format. It’s manual states it to support MPEG-4/AVC content up to 1080p (from file on USB, or streamed), making the MKV format support even better. MKV is a very flexible multimedia format that is used widely for High-definition content (also a very widely used format for pirated movies etc.).  Interesting stuff, sadly DivX seem unsupported which seem both strange and sad.