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Some .mkv files have been created with header compression, which prevents their playback on devices that do not support that feature. Unfortunately the list of such devices is long. Removing the header compression will allow those videos to play on those devices. If you receive a message that the “File format is not supported” when playing back a .mkv file, first run MediaInfo which will indicate if the file has header compression and if so use this process to remove it.
Remuxing does not recode the video file, it just recombines and reorganizes the existing video file digital information, changing only the way the digital information is arranged in the file. The bits and bytes that make up the video and audio part of the file are not changed and therefore are not degraded in any way - quality of the remuxed file is identical to the original.
The demuxing/remuxing process takes less than 30 seconds of computer time per Gigabyte (depending on the speed of your computer). Only slightly longer than the amount of time it takes to make a copy of the original video file.
Download and install MKVToolNix:
mkvToolnix - mkvmerge ( http://www.bunkus.org/videotools/mkvtoolnix/ )
Run mkvmerge GUI
Add the MKV file by Drag 'n Dropping into the “Input files” section or by using the “add” button.
a. Open the “Extra options” tab.
b. Highlight each Track.
c. Change the “Compression” dropdown to “none”.
d. Repeat steps b & c until all tracks are set to “none” (see Notes)
Note1: Some tracks do not use this setting and will not allow it to be changed.
Note2: All video, audio, subtitles (subtitles are actually video tracks), and any other track that will allow “Compression” to be changed, must be changed to “none” to insure that the video will play properly.
a.) In the “Output Location” box enter the path and file name for the final MKV file, use the browse button to save to a different folder or use the default location and file name (do not attempt to overwrite the original file).
b.) Click “Start muxing” to remux and save the new MKV file.
When muxing completes, close mkvMerge and play the file with your favorite media player or standalone device. The original file may be deleted when the new file is tested and deemed proper.