10l trocadero: ZMBV encoder used zero score to detect whether block should be

XORed with source one or not, which went wrong with new block comparing code.
So track this condition explicitly.

Originally committed as revision 20558 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/zmbvenc.c

@@ -61,15 +61,19 @@ static int score_tab[256];
  * XXX should be optimized and moved to DSPContext
  * TODO handle out of edge ME
  */
-static inline int block_cmp(uint8_t *src, int stride, uint8_t *src2, int stride2, int bw, int bh)
+static inline int block_cmp(uint8_t *src, int stride, uint8_t *src2, int stride2, int bw, int bh, int *xored)
 {
     int sum = 0;
     int i, j;
     uint8_t histogram[256]={0};
 
+    *xored = 0;
     for(j = 0; j < bh; j++){
-        for(i = 0; i < bw; i++)
-            histogram[src[i] ^ src2[i]]++;
+        for(i = 0; i < bw; i++){
+            int t = src[i] ^ src2[i];
+            histogram[t]++;
+            *xored |= t;
+        }
         src += stride;
         src2 += stride2;
     }
@@ -84,21 +88,21 @@ static inline int block_cmp(uint8_t *src, int stride, uint8_t *src2, int stride2
  * TODO make better ME decisions
  */
 static int zmbv_me(ZmbvEncContext *c, uint8_t *src, int sstride, uint8_t *prev, int pstride,
-                    int x, int y, int *mx, int *my)
+                    int x, int y, int *mx, int *my, int *xored)
 {
     int dx, dy, tx, ty, tv, bv, bw, bh;
 
     *mx = *my = 0;
     bw = FFMIN(ZMBV_BLOCK, c->avctx->width - x);
     bh = FFMIN(ZMBV_BLOCK, c->avctx->height - y);
-    bv = block_cmp(src, sstride, prev, pstride, bw, bh);
+    bv = block_cmp(src, sstride, prev, pstride, bw, bh, xored);
     if(!bv) return 0;
     for(ty = FFMAX(y - c->range, 0); ty < FFMIN(y + c->range, c->avctx->height - bh); ty++){
         for(tx = FFMAX(x - c->range, 0); tx < FFMIN(x + c->range, c->avctx->width - bw); tx++){
             if(tx == x && ty == y) continue; // we already tested this block
             dx = tx - x;
             dy = ty - y;
-            tv = block_cmp(src, sstride, prev + dx + dy*pstride, pstride, bw, bh);
+            tv = block_cmp(src, sstride, prev + dx + dy*pstride, pstride, bw, bh, xored);
             if(tv < bv){
                  bv = tv;
                  *mx = dx;
@@ -173,7 +177,7 @@ static int encode_frame(AVCodecContext *avctx, uint8_t *buf, int buf_size, void
             work_size += avctx->width;
         }
     }else{
-        int x, y, bh2, bw2;
+        int x, y, bh2, bw2, xored;
         uint8_t *tsrc, *tprev;
         uint8_t *mv;
         int mx, my, bv;
@@ -192,11 +196,11 @@ static int encode_frame(AVCodecContext *avctx, uint8_t *buf, int buf_size, void
                 tsrc = src + x;
                 tprev = prev + x;
 
-                bv = zmbv_me(c, tsrc, p->linesize[0], tprev, c->pstride, x, y, &mx, &my);
-                mv[0] = (mx << 1) | !!bv;
+                bv = zmbv_me(c, tsrc, p->linesize[0], tprev, c->pstride, x, y, &mx, &my, &xored);
+                mv[0] = (mx << 1) | !!xored;
                 mv[1] = my << 1;
                 tprev += mx + my * c->pstride;
-                if(bv){
+                if(xored){
                     for(j = 0; j < bh2; j++){
                         for(i = 0; i < bw2; i++)
                             c->work_buf[work_size++] = tsrc[i] ^ tprev[i];