[Matroska-devel] CodecSpecs

Moritz Bunkus moritz at bunkus.org
Mon Jan 10 09:22:47 CET 2011


On Monday 10 January 2011 02:24:08 Santiago Jimeno wrote:

> Regarding MLP-TrueHD, I made what you tell me in your e-mail, but without
> success.
> MLP contain in the blocks the whole header beginning with F8726FBB, but
> TrueHd doesn't contain the first 4 bytes of the header (F8726FBA).

My guess is that you don't take header removal compression into account

The code in mkvmerge is the same for MLP and TrueHD. In fact, it's the
same source file with very few conditional code for distinction between

> The samples that I am using are:
> http://samples.mplayerhq.hu/A-codecs/TrueHD/TrueHD%20Sample%201%20(Final%20
> Fantasy%20VII%20Advent%20Children).mkv
> http://samples.mplayerhq.hu/A-codecs/TrueHD/TrueHD%20Sample%202%20(Evangel
> ion%201.11%20You%20Are%20(Not)%20Alone).mkv

Ok those do not use header removal compression. Interesting. Let's see:

[0 mbunkus at ls-bs-ws4 ~/dl] mkvinfo -v -v TrueHD\ Sample\ 1\ \(Final\ Fantasy\ 
VII\ Advent\ Children\).mkv| grep 'track number 2' | head -n 1
| + SimpleBlock (track number 2, 1 frame(s), timecode 0.000s = 00:00:00.000) 
at 154845

So the very first audio track's frame starts at position 154845 in the
file. Using a hex editor the bytes are really not the sync word. This
could be a bug in mkvmerge. I'll try to investigate this sometime this

> I have observed that you with Mkvtool can calculate the duration of
> MLP-TrueHd audio file to make the MKA file.
> It has been impossible for my to calculate the duration with the data
> provided by the original audio file.
> Would you be able to help me in this?

I don't have time to explain (I'm at work), but all the relevant code is
in these two files:


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