[Mp4-tech] FGS code in microsoft-v2.5-040207-NTU

[ChengHsin Hsu]

Dear All,
I probably overlooked something...I do not understand what does  
rec_value stand for. Looks to me the following code section increases  
the zero-bin by 1 at both positive and negative?
Thanks,
Chenghsin
VoidCVideoObjectDecoder::Recoverbp(Int m, Int *diff, Int *sign,Int  
*DCT_block )
{
...........
         decoded_level = enh_block_data[m].decoded_level;
         rec_value = (decoded_level>2) ? (1<<(decoded_level-3)) :  
0;        for(i=0;i<BLOCK_SQUARE_SIZE;i++){
                 if (diff[i]) diff[i] += rec_value;
         }
---------Original Message------------------
Hi All,
Just started reading the fgs code in microsoft-v2.5-040207-NTU. I
noticed both the encoder/decoder explicitly ignore two of the least
significant bitplanes. Tried to find any comments in txt files, but
failed. There is an in-line comment saying this is a fix of a encoder
bug.
Is there any particular reason of doing this? I did a quick
experimentation, putting these two bps can give me several dB gain in
terms of PSNR.
Any hints are highly appreciated.
Thanks,
Chenghsin