[Ffmpeg-devel] Re: [RFC] mpeg2 422 encoding.

[Michael Niedermayer]

Hi

On Sat, Apr 01, 2006 at 03:03:37AM +0200, Baptiste COUDURIER wrote:
[...]
> @@ -616,8 +636,12 @@ void mpeg1_encode_mb(MpegEncContext *s,
>                  }
>                  s->mv_bits+= get_bits_diff(s);
>              }
> -            if(cbp)
> -                put_bits(&s->pb, mbPatTable[cbp][1], mbPatTable[cbp][0]);
> +            if(cbp) {
> +                put_bits(&s->pb, mbPatTable[cbp & 0x3f][1], mbPatTable[cbp & 0x3f][0]);
> +                if (!s->chroma_y_shift) {
> +                    put_bits(&s->pb, 2, (cbp >> 6) & 3);
> +                }
> +            }
>              s->f_count++;
>          } else{
>              static const int mb_type_len[4]={0,3,4,2}; //bak,for,bi
> @@ -695,11 +719,15 @@ void mpeg1_encode_mb(MpegEncContext *s,
>                  }
>              }
>              s->mv_bits += get_bits_diff(s);
> -            if(cbp)
> -                put_bits(&s->pb, mbPatTable[cbp][1], mbPatTable[cbp][0]);
> +            if(cbp) {
> +                put_bits(&s->pb, mbPatTable[cbp & 0x3f][1], mbPatTable[cbp & 0x3f][0]);
> +                if (!s->chroma_y_shift) {
> +                    put_bits(&s->pb, 2, (cbp >> 6) & 3);
> +                }
> +            }

these are wrong, the following is correct

if (!s->chroma_y_shift) {
    put_bits(&s->pb, mbPatTable[cbp>>2][1], mbPatTable[cbp>>2][0]);
    put_bits(&s->pb, 2, cbp & 3);
}else
    put_bits(&s->pb, mbPatTable[cbp][1], mbPatTable[cbp][0]);


also note that the whole 422 encoding support must not slow the much more
common 420 down by a "meassureable" amount

[...]

-- 
Michael