[libav-bugs] [Bug 431] The Lagarith decoder included in libav is faulty. It removes some intentional black frames, so it does not reproduce frame for frame the content provided.

bugzilla-daemon at aruru.libav.org bugzilla-daemon at aruru.libav.org
Tue Jan 22 03:10:13 CET 2013


https://bugzilla.libav.org/show_bug.cgi?id=431

Cosmin Gurau <cosmingurau at gmail.com> changed:

           What    |Removed                     |Added
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                URL|                            |http://we.tl/k2Ewf4slZS

--- Comment #1 from Cosmin Gurau <cosmingurau at gmail.com> 2013-01-22 03:10:13 CET ---
http://we.tl/k2Ewf4slZS The attatchment option doesn't work, so please use this
link.

I have noticed this bug while using Handbrake's nightly build. 

I was converting my short film from the Lagarith format using the nightly
version (using pretty basic settings), when I noticed that some artistically
intentional quick black flashes from a certain scene had been completely
removed... So the footage was "cleaned" of the black flashes. They were black
frames, actually. And they were just removed. 

I converted it again, different settings, to the same effect.

The folks at Handbrake did the same, using a sample video I sent them, that I
am sending to you too, and concluded that it was a Lagarith decoding specific
issue(thus libav), as any other situation kept the flashes intact, when the
original Lagarith file was encoded with VirtualDub, to various formats, and
THEN to h.264 using Handbrake. In conclusion, only the combination Lagarith -
Handbrake yielded the bug, the removal of the sudden black frames. 

So, the only possible conclusion is that libav's implementation of Lagarith
Lossless Codec is faulty.

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