gecko/media/liboggz/key_frame_seek.patch

diff --git a/media/liboggz/include/oggz/oggz_seek.h b/media/liboggz/include/oggz/oggz_seek.h
--- a/media/liboggz/include/oggz/oggz_seek.h
+++ b/media/liboggz/include/oggz/oggz_seek.h
@@ -489,9 +489,22 @@ int oggz_set_data_start (OGGZ * oggz, og
  * \retval -1 on failure (unit_target is not within range)
  */
 ogg_int64_t
 oggz_bounded_seek_set (OGGZ * oggz,
                        ogg_int64_t unit_target,
                        ogg_int64_t offset_begin,
                        ogg_int64_t offset_end);
 
+/**
+ * Seeks to the first key frame before unit_target, in the range
+ * [offset_begin, offset_end]. serial_nos contains an array of size serial_nos
+ * of serialnos of the streams which need to be seeked.
+ */
+ogg_int64_t
+oggz_keyframe_seek_set(OGGZ * oggz,
+                       long* serial_nos,
+                       int num_serialno,
+                       ogg_int64_t unit_target,
+                       ogg_int64_t offset_begin,
+                       ogg_int64_t offset_end);
+
 #endif /* __OGGZ_SEEK_H__ */
diff --git a/media/liboggz/src/liboggz/oggz_seek.c b/media/liboggz/src/liboggz/oggz_seek.c
--- a/media/liboggz/src/liboggz/oggz_seek.c
+++ b/media/liboggz/src/liboggz/oggz_seek.c
@@ -931,8 +931,131 @@ oggz_seek_byorder (OGGZ * oggz, void * t
 
 long
 oggz_seek_packets (OGGZ * oggz, long serialno, long packets, int whence)
 {
   return OGGZ_ERR_DISABLED;
 }
 
 #endif
+
+// Returns 1 if any of the elements of array |a|, which is of length |n|,
+// contain the value |val|. Otherwise returns 0.
+static int
+is_any(ogg_int64_t* a, int n, ogg_int64_t val)
+{
+  int i;
+  for (i=0; i<n; i++) {
+    if (a[i] == val) {
+      return 1;
+    }
+  }
+  return 0;    
+}
+
+// Returns the index of the element in array |a|, which is of length |n|,
+// which contains the value |val|, or -1 of it's not present.
+static int
+find(long* a, int n, ogg_int64_t val)
+{
+  int i;
+  for (i=0; i<n; i++) {
+    if (a[i] == val) {
+      return i;
+    }
+  }
+  return -1;    
+}
+
+// Returns the element with the smallest value in array |a|, which is
+// of length |n|.
+static ogg_int64_t
+minimum(ogg_int64_t* a, int n) {
+  ogg_int64_t m = 0x7FFFFFFFFFFFFFFF;
+  int i;
+  for (i=0; i<n; i++) {
+    if (a[i] < m) {
+      m = a[i];
+    }
+  }
+  return m;
+}
+
+ogg_int64_t
+oggz_keyframe_seek_set(OGGZ * oggz,
+                       long* serial_nos,
+                       int num_serialno,
+                       ogg_int64_t unit_target,
+                       ogg_int64_t offset_begin,
+                       ogg_int64_t offset_end)
+{
+  oggz_off_t offset_at;
+  oggz_off_t offset_next;
+  ogg_int64_t granule_at;
+  ogg_int64_t unit_at;
+  ogg_int64_t key_granule_at, key_unit_at;
+  long serialno;
+  ogg_page * og;
+  int granule_shift = 0, idx;
+  ogg_int64_t* key_frames = 0;
+  
+  unit_at = oggz_bounded_seek_set(oggz,
+                                  unit_target,
+                                  offset_begin,
+                                  offset_end);
+  // Time isn't in the specified offset range, fail.
+  if (unit_at == -1)
+    return -1;
+
+  // We've seeked to beginning, we're at a key frame.
+  if (unit_at == 0)
+    return 0; 
+
+  // Backup this, in case we need to fail.
+  offset_at = oggz->offset;
+
+  key_frames = oggz_malloc(sizeof(ogg_int64_t) * num_serialno);
+  if (!key_frames) {
+    // Malloc failure. We can still exit with the seek finishing at a non
+    // key frame.
+    return unit_at;
+  }
+  memset(key_frames, -1, sizeof(ogg_int64_t) * num_serialno);
+
+  // Find the key frame offset for every stream.
+  og = &oggz->current_page;
+  while (is_any(key_frames, num_serialno, -1)) {
+    do {
+      offset_next = oggz_get_prev_start_page (oggz, og, &granule_at, &serialno);
+      if (offset_next <= 0 || granule_at == 0) {
+        // At beginning of file, or some other failure. Return with
+        // non-key frame seek if possible.
+        oggz_free(key_frames);
+        offset_at = oggz_reset (oggz, offset_at, unit_at, SEEK_SET);
+        return (offset_at == -1) ? -1 : unit_at;
+      }
+    } while (granule_at < 0);
+
+    idx = find(serial_nos, num_serialno, serialno);
+    if (idx == -1 || key_frames[idx] != -1)
+      continue;
+
+    granule_shift = oggz_get_granuleshift(oggz, serialno);
+    key_granule_at = (granule_at >> granule_shift) << granule_shift;
+    key_unit_at = oggz_get_unit(oggz, serialno, key_granule_at);
+
+    if (key_unit_at < unit_target)
+      key_frames[idx] = key_unit_at;
+  }
+
+  // Seek to 100ms before the earliest of all the streams' key frames.
+  // This is so that after the seek, the decoder will defintately return frames
+  // at or before get the key frame. Without this, some decoders will return
+  // frames which start after the specified time - after the key frame.
+  key_unit_at = minimum(key_frames, num_serialno);
+  unit_at = oggz_bounded_seek_set(oggz,
+                                  MAX((key_unit_at - 100), 0),
+                                  offset_begin,
+                                  offset_end);
+  oggz_free(key_frames);
+
+  return unit_at;
+}