size[0-3] are not initialized (and can get random negative trash

values), so the comparison with vs_total_ac_bits is messed up on the
first couple loop iterations, leading to AC underflows.

the b->prev[] pointers were not being maintained correctly. We
potentially have to update b->prev[] both before and after the area
whose VLC length is getting adjusted.

this also might fix the ppc regression failure?

patch by (Dan Maas <dmaas maasdigital com>)

Originally committed as revision 5064 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/dv.c

@@ -731,7 +731,7 @@ static inline void dv_guess_qnos(EncBlockInfo* blks, int* qnos)
     int i, j, k, a, prev, a2;
     EncBlockInfo* b;
 
-    size[4]= 1<<24;
+    size[0] = size[1] = size[2] = size[3] = size[4] = 1<<24;
     do {
        b = blks;
        for (i=0; i<5; i++) {
@@ -753,11 +753,14 @@ static inline void dv_guess_qnos(EncBlockInfo* blks, int* qnos)
                            prev= k;
                        } 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++);
+                                for(a2=a+1; b->next[k] >= mb_area_start[a2+1]; a2++)
+                                    b->prev[a2] = prev;
                                 assert(a2<4);
                                 assert(b->mb[b->next[k]]);
                                 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]]);
+                                for(; (b->prev[a2]==k) && (a2<4); a2++)
+                                        b->prev[a2] = prev;
                            }
                            b->next[prev] = b->next[k];
                        }

tests/ffmpeg.regression.ref

@@ -133,9 +133,9 @@ stddev: 23.20 PSNR:20.81 bytes:7602176
 3533710 ./data/a-snow53.avi
 799d3db687f6cdd7a837ec156efc171f *./data/out.yuv
 stddev:  0.00 PSNR:99.99 bytes:7602176
-229e5f8d1f386d0cf84f629be7d74955 *./data/a-dv.dv
+a071e3aa523e0f91fce08bdba0d47199 *./data/a-dv.dv
 7200000 ./data/a-dv.dv
-0ac51c62d3c2a4bacf216ea73050485e *./data/out.yuv
+a99de8648a78970065b834219d9fa27a *./data/out.yuv
 stddev:  9.10 PSNR:28.94 bytes:7602176
 bd0db310a36ad94bcd4448abe0a88368 *./data/a-svq1.mov
 1379827 ./data/a-svq1.mov

tests/libav.regression.ref

@@ -28,7 +28,7 @@ e4ed8d635d867e2f5980fd9c73c9cf3d *./data/b-libav.mov
 8bf16d40a2ec19fa36b124a928e47e23 *./data/b-libav.nut
  332358 ./data/b-libav.nut
 ./data/b-libav.nut CRC=0xccab3a27
-973886f2acd79e6785e0f31519d721cf *./data/b-libav.dv
+5a040cc1353f17f6a7305e972c0667d0 *./data/b-libav.dv
 3600000 ./data/b-libav.dv
 ./data/b-libav.dv CRC=0x5e1f4cdc
 9a9da315747599f7718cc9a9a09c21ff *./data/b-libav.pbm