[FFmpeg-devel] [PATCH] Fraps fix

[Roine Gustafsson]

Fraps sometimes glitches with current SVN because symbols with zero  
count is not added to the huffman tree despite Kostya's stern  
warning: <http://wiki.multimedia.cx/index.php?title=Fraps>
It seems VP6 and Fraps differ in this regard (both share the huffman  
tree build code)
None of the current Fraps samples on mplayerhq seem to exhibit this  
bug; here is a sample that does: <http://www.mediafire.com/?e4dqezhxcm2>

Suggested patch attached. This correctly plays the broken one, all  
Fraps samples on mplayerhq and all VP6 samples that worked before.


   /Roine


Index: libavcodec/huffman.c
===================================================================
--- libavcodec/huffman.c	(revision 12184)
+++ libavcodec/huffman.c	(working copy)
@@ -28,12 +28,14 @@
  #define HNODE -1


-static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t  
*xlat, Node *nodes, int node, uint32_t pfx, int pl, int *pos)
+static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t  
*xlat,
+                           Node *nodes, int node, uint32_t pfx, int pl,
+                           int *pos, int include_zero_count)
  {
      int s;

      s = nodes[node].sym;
-    if(s != HNODE || !nodes[node].count){
+    if(s != HNODE || (!include_zero_count && !nodes[node].count)){
          bits[*pos] = pfx;
          lens[*pos] = pl;
          xlat[*pos] = s;
@@ -41,20 +43,20 @@
      }else{
          pfx <<= 1;
          pl++;
-        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx,  
pl, pos);
+        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx,  
pl, pos, include_zero_count);
          pfx |= 1;
-        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1,  
pfx, pl, pos);
+        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1,  
pfx, pl, pos, include_zero_count);
      }
  }

-static int build_huff_tree(VLC *vlc, Node *nodes, int head)
+static int build_huff_tree(VLC *vlc, Node *nodes, int head, int  
include_zero_count)
  {
      uint32_t bits[256];
      int16_t lens[256];
      uint8_t xlat[256];
      int pos = 0;

-    get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos);
+    get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos,  
include_zero_count);
      return init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4,  
xlat, 1, 1, 0);
  }

@@ -62,9 +64,11 @@
  /**
   * nodes size must be 2*nb_codes
   * first nb_codes nodes.count must be set
+ * @param include_zero_count boolean; set to include zero symbol counts
   */
  int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
-                       Node *nodes, huff_cmp_t cmp, int hnode_first)
+                       Node *nodes, huff_cmp_t cmp, int hnode_first,
+                       int include_zero_count)
  {
      int i, j;
      int cur_node;
@@ -97,7 +101,7 @@
          }
          cur_node++;
      }
-    if(build_huff_tree(vlc, nodes, nb_codes*2-2) < 0){
+    if(build_huff_tree(vlc, nodes, nb_codes*2-2, include_zero_count)  
< 0){
          av_log(avctx, AV_LOG_ERROR, "Error building tree\n");
          return -1;
      }
Index: libavcodec/huffman.h
===================================================================
--- libavcodec/huffman.h	(revision 12184)
+++ libavcodec/huffman.h	(working copy)
@@ -34,6 +34,7 @@

  typedef int (*huff_cmp_t)(const void *va, const void *vb);
  int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
-                       Node *nodes, huff_cmp_t cmp, int hnode_first);
+                       Node *nodes, huff_cmp_t cmp, int hnode_first,
+                       int include_zero_count);

  #endif /* FFMPEG_HUFFMAN_H */
Index: libavcodec/fraps.c
===================================================================
--- libavcodec/fraps.c	(revision 12184)
+++ libavcodec/fraps.c	(working copy)
@@ -94,7 +94,7 @@
      for(i = 0; i < 256; i++)
          nodes[i].count = bytestream_get_le32(&src);
      size -= 1024;
-    if (ff_huff_build_tree(s->avctx, &vlc, 256, nodes, huff_cmp, 0)  
< 0)
+    if (ff_huff_build_tree(s->avctx, &vlc, 256, nodes, huff_cmp, 0,  
1) < 0)
          return -1;
      /* we have built Huffman table and are ready to decode plane */

Index: libavcodec/vp6.c
===================================================================
--- libavcodec/vp6.c	(revision 12184)
+++ libavcodec/vp6.c	(working copy)
@@ -225,7 +225,7 @@
      }

      /* then build the huffman tree accodring to probabilities */
-    ff_huff_build_tree(s->avctx, vlc, size, nodes, vp6_huff_cmp, 1);
+    ff_huff_build_tree(s->avctx, vlc, size, nodes, vp6_huff_cmp, 1, 0);
  }

  static void vp6_parse_coeff_models(vp56_context_t *s)



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