View Single Post
Old 10th July 2018, 18:56   #5243  |  Link
Mosu
MKVToolNix author
 
Mosu's Avatar
 
Join Date: Sep 2002
Location: Braunschweig, Germany
Posts: 4,278
If they know the codec type and order of tracks, they could create a second file with the same track types and track order. Then use a hex editor and combine the track headers (everything before the first cluster) from the second file with the clusters from the encrypted file.

One problem will be CodecPrivate content. This won't be 100% identical in the second file you've created. However, you might get away with additional steps:
  1. Extract the video track from the combined file with "--raw"
  2. Remux that extracted data with mkvmerge

This might work if it's h.264 or h.265 and the SPS/PPS are part of the bitstream as mkvmerge will then be able to re-create the CodecPrivate from the bitstream.

Things get somewhat more complicated with AAC and CodecPrivate. In that case I'd try hard to simply get an audio track to mux with the same stream parameters (number of channels, sample rate, profile) and use the resulting track headers.

After all, they should start making regular backups — the best insurance against data loss of any kind, including crypto ransomware.
__________________
Latest MKVToolNix is v83.0

If I ever ask you to upload something, please use my file server.
Mosu is offline