[FFmpeg-devel] [PATCH] H.264: cleanup decode_residual()

[Michael Niedermayer]

On Mon, Mar 02, 2009 at 09:11:24PM -0500, Alex Converse wrote:
> easier to follow and a very very minor speedup on gcc-4.3.2

> diff --git a/libavcodec/h264.c b/libavcodec/h264.c
> index 91f20c9..560f964 100644
> --- a/libavcodec/h264.c
> +++ b/libavcodec/h264.c
> @@ -4187,17 +4187,16 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
>              //first coefficient has suffix_length equal to 0 or 1
>              if(prefix<14){ //FIXME try to build a large unified VLC table for all this
>                  if(suffix_length)
> -                    level_code= (prefix<<suffix_length) + get_bits(gb, suffix_length); //part
> +                    level_code= (prefix<<1) + get_bits(gb, 1); //part
>                  else
> -                    level_code= (prefix<<suffix_length); //part
> +                    level_code= prefix; //part
>              }else if(prefix==14){
>                  if(suffix_length)
> -                    level_code= (prefix<<suffix_length) + get_bits(gb, suffix_length); //part
> +                    level_code= (prefix<<1) + get_bits(gb, 1); //part
>                  else
>                      level_code= prefix + get_bits(gb, 4); //part

above is ok


>              }else{
> -                level_code= (15<<suffix_length) + get_bits(gb, prefix-3); //part
> -                if(suffix_length==0) level_code+=15; //FIXME doesn't make (much)sense
> +                level_code= 30 + get_bits(gb, prefix-3); //part
>                  if(prefix>=16)
>                      level_code += (1<<(prefix-3))-4096;
>              }

can you explain why suffix_length here has to be 1 ?

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

Many things microsoft did are stupid, but not doing something just because
microsoft did it is even more stupid. If everything ms did were stupid they
would be bankrupt already.
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