[FFmpeg-devel] jframe

Benjamin Larsson banan
Thu Jun 7 12:01:11 CEST 2007


Reimar D?ffinger skrev:
> Hello,
> On Wed, May 30, 2007 at 10:59:54PM +0200, matthieu castet wrote:
>>> On Wed, May 30, 2007 at 05:30:57PM +0300, Ivan Kalvachev wrote:
>>>> 2007/5/30, Michael Niedermayer <michaelni at gmx.at>:
>>>>>> A google search
>>>>>> comes up with nothing. How do you know that j-type frames are called 'j-type
>>>>>> frames'?
>>>>> we dont, and they are also almost certainly not called j frames by MS
>>>> They call them X8 (or intra X8).
>>>> Kostya also said they refer to them in this way in the vc1 advanced profile.
>> There also a callgraph of the MS codec : 
>> http://multimedia.cx/eggs/images/dcng-frame18-callgraph.png
> Does someone know details about the (Local?)Huffman stuff that X8 uses?
> Is this in use in some other places as well? Is there maybe even already
> some code somewhere?
> I hate huffman so I don't really want to play with that *g*
> Greetings,
> Reimar D?ffinger

I have meant to write some of my research on this but I haven't had the 
time yet. The libwmv8.so that contain X8 frame decoding can be found in 
Linspires Freespire distribution. 
http://wiki.freespire.org/index.php/Download_Freespire to download the 
iso. (Use the cloop utils to extract the live image or just burn the cd 
and boot to get the so's.) The libwma8.so isn't stripped so it is very 
easy to identify the code that is used to decode the X8 frames. With 
this said I'm not actively trying to RE the code I'm just describing one 
way to do it. Regarding your question, I do think the X8 huffman stuff 
would be able to use the FFmpeg vlc stuff. At least for the vlctable 
building and stream decoding.

Benjamin Larsson

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