Native VP8 decoder.

Patch by David Conrad <lessen42 gmail com> and myself.

Originally committed as revision 23719 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 75 insertions, 0 deletions

diff --git a/libavcodec/vp56.h b/libavcodec/vp56.h
index 0b6f2a8..4eb414b 100644
--- a/libavcodec/vp56.h
+++ b/libavcodec/vp56.h
@@ -237,6 +237,12 @@ static inline int vp56_rac_get(VP56RangeCoder *c)
     return bit;
 }
 
+// rounding is different than vp56_rac_get, is vp56_rac_get wrong?
+static inline int vp8_rac_get(VP56RangeCoder *c)
+{
+    return vp56_rac_get_prob(c, 128);
+}
+
 static inline int vp56_rac_gets(VP56RangeCoder *c, int bits)
 {
     int value = 0;
@@ -248,12 +254,46 @@ static inline int vp56_rac_gets(VP56RangeCoder *c, int bits)
     return value;
 }
 
+static inline int vp8_rac_get_uint(VP56RangeCoder *c, int bits)
+{
+    int value = 0;
+
+    while (bits--) {
+        value = (value << 1) | vp8_rac_get(c);
+    }
+
+    return value;
+}
+
+// fixme: add 1 bit to all the calls to this?
+static inline int vp8_rac_get_sint(VP56RangeCoder *c, int bits)
+{
+    int v;
+
+    if (!vp8_rac_get(c))
+        return 0;
+
+    v = vp8_rac_get_uint(c, bits);
+
+    if (vp8_rac_get(c))
+        v = -v;
+
+    return v;
+}
+
+// P(7)
 static inline int vp56_rac_gets_nn(VP56RangeCoder *c, int bits)
 {
     int v = vp56_rac_gets(c, 7) << 1;
     return v + !v;
 }
 
+static inline int vp8_rac_get_nn(VP56RangeCoder *c)
+{
+    int v = vp8_rac_get_uint(c, 7) << 1;
+    return v + !v;
+}
+
 static inline int vp56_rac_get_tree(VP56RangeCoder *c,
                                     const VP56Tree *tree,
                                     const uint8_t *probs)
@@ -267,4 +307,39 @@ static inline int vp56_rac_get_tree(VP56RangeCoder *c,
     return -tree->val;
 }
 
+/**
+ * This is identical to vp8_rac_get_tree except for the possibility of starting
+ * on a node other than the root node, needed for coeff decode where this is
+ * used to save a bit after a 0 token (by disallowing EOB to immediately follow.)
+ */
+static inline int vp8_rac_get_tree_with_offset(VP56RangeCoder *c, const int8_t (*tree)[2],
+                                               const uint8_t *probs, int i)
+{
+    do {
+        i = tree[i][vp56_rac_get_prob(c, probs[i])];
+    } while (i > 0);
+
+    return -i;
+}
+
+// how probabilities are associated with decisions is different I think
+// well, the new scheme fits in the old but this way has one fewer branches per decision
+static inline int vp8_rac_get_tree(VP56RangeCoder *c, const int8_t (*tree)[2],
+                                   const uint8_t *probs)
+{
+    return vp8_rac_get_tree_with_offset(c, tree, probs, 0);
+}
+
+// DCTextra
+static inline int vp8_rac_get_coeff(VP56RangeCoder *c, const uint8_t *prob)
+{
+    int v = 0;
+
+    do {
+        v = (v<<1) + vp56_rac_get_prob(c, *prob++);
+    } while (*prob);
+
+    return v;
+}
+
 #endif /* AVCODEC_VP56_H */