[FFmpeg-soc] SOC Qualifiction tasks

[Michael Niedermayer]

On Sat, Mar 15, 2008 at 08:30:40PM +0100, Bartlomiej Wolowiec wrote:
> On sobota, 15 marca 2008, Justin Ruggles wrote:
[...]
> > 7. Error conclealment. Simple error concealment is fairly trivial. For
> > more robust detection and concealment, Michael made some great
> > suggestions for guidelines.  It would require some reworking of the AC3
> > parser.
> 
> Can you give me some more explanations on this topic, because I think I don't 
> understand what do you mean properly

Now if i would remember what i said in that mail or could find that mail ...

Anyway
E-AC3 says:
E3.2 Error Detection and Concealment
Enhanced AC-3 decoders are required to implement error detection based on the bit stream CRC
word. Enhanced AC-3 bit streams contain only one CRC word, which covers the entire frame.
When decoding bit streams that use the Enhanced AC-3 bit stream syntax, Enhanced AC-3
decoders must verify the CRC word prior to decoding any of the blocks in the frame.
    If the CRC word for an Enhanced AC-3 bit stream is found to be invalid, all blocks in the
frame must be substituted with an appropriate error concealment signal. For most applications,
this can be easily accomplished by simply repeating the last known-good block (before the
overlap-add window process).
----

And thats a good goal ...
Besides this it would be nice if we could detect errors faster than checking
crcs (wrong vlc, too long/ short bitstream), but i do not know if this can be
done. If not forget about it and just implement error concealment per CRCs.
Thats IMHO as i dont remember what i said about E-AC3 EC and maybe justin has
some comments as well, i just replied as it seems justin didnt exactly reply.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Breaking DRM is a little like attempting to break through a door even
though the window is wide open and the only thing in the house is a bunch
of things you dont want and which you would get tomorrow for free anyway
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