[Ffmpeg-devel] Re: [Ffmpeg-cvslog] CVS: ffmpeg/libavcodec dv.c, 1.72, 1.73

[Roman Shaposhnick]

On Thu, Feb 23, 2006 at 09:56:55AM +0100, Michael Niedermayer CVS wrote:
> Update of /cvsroot/ffmpeg/ffmpeg/libavcodec
> In directory mail:/var2/tmp/cvs-serv3315/libavcodec
> 
> Modified Files:
> 	dv.c 
> Log Message:
> fixing dv_guess_qnos()
> roman, dont hesitate to reverse this and solve it differntly if you want ...

  I wish I could be as quick :-( Anyway, this looks almost exactly like what I
  had in mind. Thanks for commiting it. A could of questions, though:

>                         } else {
> +                           if(b->next[k] >= mb_area_start[a+1] && b->next[k]<64){
> +                                for(a2=a+1; b->next[k] >= mb_area_start[a2+1]; a2++);
> +                                assert(a2<4);
> +                                assert(b->mb[b->next[k]]);

  Why these particular asserts ? 

> +                                b->bit_size[a2] += dv_rl2vlc_size(b->next[k] - prev - 1, b->mb[b->next[k]])
> +                                                  -dv_rl2vlc_size(b->next[k] -    k - 1, b->mb[b->next[k]]);
> +                           }
>                             b->next[prev] = b->next[k];
>                         }
>                      }
> @@ -760,8 +767,26 @@
>               }
>            }
>         }
> -    } while ((vs_total_ac_bits < size[0] + size[1] + size[2] + size[3] + size[4]) &&
> -             (qnos[0]|qnos[1]|qnos[2]|qnos[3]|qnos[4]));
> +       if(vs_total_ac_bits >= size[0] + size[1] + size[2] + size[3] + size[4])
> +            return;
> +    } while (qnos[0]|qnos[1]|qnos[2]|qnos[3]|qnos[4]);
> +
> +
> +    for(a=2; a==2 || vs_total_ac_bits < size[0]; a+=a){
> +        b = blks;
> +        size[0] = 0;
> +        for (j=0; j<6*5; j++, b++) {
> +            prev= b->prev[0];
> +            for (k= b->next[prev]; k<64; k= b->next[k]) {
> +                if(b->mb[k] < a && b->mb[k] > -a){
> +                    b->next[prev] = b->next[k];
> +                }else{
> +                    size[0] += dv_rl2vlc_size(k - prev - 1, b->mb[k]);
> +                    prev= k;
> +                }
> +            }
> +        }
> +    }

   
   Are you sure that we need this chunk of code ? My concern is -- in case
   where encoder maxes out on all QNOs being 0s -- there's very little we
   can to do salvage the situation anyway. Or did you have another idea 
   when creating this chunk of code ?

Thanks,
Roman.