[FFmpeg-devel] [PATCH] RoQ video encoder (take 4)

[Vitor]

Hi

Eric Lasota wrote:
> Michael Niedermayer wrote:
>   
>> this if() does seem unneeded
>> btw, what is the purpose of the numCB4 == 256 special case above this if()?
>>   
>>     
>
> The two codebook counts are stored as a 16-bit value, but the way Quake 
> 3 interprets it is as follows:
>
> if (!roq_flags) {
>     two = four = 256;
> } else {
>     two  = roq_flags>>8;
>     if (!two) two = 256;
>     four = roq_flags&0xff;
> }
>
> The problem with this is that if the result has, for example, 254 2x2 
> entries and 256 4x4 entries, Quake 3 will interpret that as 254 2x2 
> entries and ZERO 4x4 entries.  Third-party decoders typically check the 
> chunk size to see if there are 4x4 entries or not, Quake 3 doesn't.  
> Consequently, the only correct way to store 256 4x4 entries is with 256 
> 2x2 entries.
>
>   

Wouldn't it be better to just encode a maximum of 255 4x4 cb entries? It 
won't broke nor quake 3 nor third party decoders and is pretty 
straightforward to code (and anyway anyone encoding with a decent 
quality won't need so many 4x4 codebooks)...

-Vitor