[Bug 784258] qtmoovrecover can't recover video

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=784258

--- Comment #19 from Thiago Sousa Santos <thiagossantos at gmail.com> ---
unfortunately I couldn't reproduce it by going back to 1.8.3. Also I don't have
nxenc or an ARM64 platform to test. Let me put some information here in case it
helps you on anyone else debugging this further.

The recovery element takes 2 inputs, one is the .mov and another is the .mrf.
In the .mov there is only the stream data, just a massive blob. It starts with
a "ftyp" and maybe some minor atoms and then there should be the 'mdat' atom
that has all the data inside it. A quick read on the quicktime format spec
should give a basic idea of how these files are structured.

To recover this file, the .mrf file actually stores header information, which
is the size, position and timing information for every sample that was stored
to the .mov file. By combining those two it is possible to create a full
mov/mp4 file that has the full headers and the data.

In your case, the mdat file seems to be longer than what the mrf headers have
stored and it will cause some extra random binary data to be placed at the end
of the file. There is one way to improve this by limiting the mdat output to
only write to disk what is actually in the mrf headers but that would only hide
the real problem that is why that extra data is in the end on the first place.
Maybe by adding some extra debgugging to your setup you can figure out where
does that come from and why there isn't headers in the mrf for that data.

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