Do the following if your player doesn?t play a .MKV file. * If you downloaded the .MKV file from the Internet, download it again from another site * If you created the .MKV file, make sure that the files inside the .MKV file use the following standard. If they don?t, create the file again > .MKV movie files must comply with the h.264 profile specification > Files must use the Main Profile or High Profile Main Profile (MP) is for SD digital TV broadcasts that use MPEG4. High Profile (HiP) is the primary profile for broadcast and disc storage applications. It is used for HD TV. The HiP format is used for Blu-ray discs DVB HDTV broadcasts. * Make sure that your files do not exceed the following level standards. > 3.2 for Main Profile files > 4.1 for High Profile files with a maximum bit rate of 20 MBit/second * If you see juddering or artifacts, encode your files again with fewer reference frames. For information about reference frames, see the end of this FAQ. For information about encoding, see the documentation provided with your video conversion software. * Make sure that you don?t use too many reference frames in a movie file: > Use up to 4 reference frames for 19201080 pixel resolution > Use up to 9 reference frames for 1280720 pixel resolution > Use up to 11 reference frames for 720576 pixel resolution or lower * Make sure that .MKA files embedded into a .MKV movie file have one of the following formats: > mp2 > mp3 > ac-3 > dts Information about reference frames The h.264 codec uses a compression technique called �reference frames� (also called reframes). The maximum number of reference frames supported by h.264 is 16. A larger number of reference frames can increase the compression quality, but they require more processor power and memory during the encoding process. When you play back an h.264 encoded video, there is a limitation on the number of reference frames. Because of the hardware limitations in the encoding and the playback stage, most people who encode video use 3-5 reference frames.