svq3 decoder by anonymous

Originally committed as revision 1845 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 44 insertions, 0 deletions

diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h
index 91c699367c..510d913ae1 100644
--- a/libavcodec/golomb.h
+++ b/libavcodec/golomb.h
@@ -25,6 +25,8 @@
  * @author Michael Niedermayer <michaelni@gmx.at>
  */
 
+#define INVALID_VLC           0x80000000
+
 extern const uint8_t ff_golomb_vlc_len[512];
 extern const uint8_t ff_ue_golomb_vlc_code[512];
 extern const  int8_t ff_se_golomb_vlc_code[512];
@@ -59,6 +61,27 @@ static inline int get_ue_golomb(GetBitContext *gb){
     }
 }
 
+static inline int svq3_get_ue_golomb(GetBitContext *gb){
+    unsigned int buf;
+    int log;
+
+    OPEN_READER(re, gb);
+    UPDATE_CACHE(re, gb);
+    buf=GET_CACHE(re, gb)|1;
+
+    if((buf & 0xAAAAAAAA) == 0)
+        return INVALID_VLC;
+
+    for(log=31; (buf & 0x80000000) == 0; log--){
+        buf = (buf << 2) - ((buf << log) >> (log - 1)) + (buf >> 30);
+    }
+
+    LAST_SKIP_BITS(re, gb, 63 - 2*log);
+    CLOSE_READER(re, gb);
+
+    return ((buf << log) >> log) - 1;
+}
+
 /**
  * read unsigned truncated exp golomb code.
  */
@@ -112,6 +135,27 @@ static inline int get_se_golomb(GetBitContext *gb){
     }
 }
 
+static inline int svq3_get_se_golomb(GetBitContext *gb){
+    unsigned int buf;
+    int log;
+
+    OPEN_READER(re, gb);
+    UPDATE_CACHE(re, gb);
+    buf=GET_CACHE(re, gb)|1;
+
+    if((buf & 0xAAAAAAAA) == 0)
+        return INVALID_VLC;
+
+    for(log=31; (buf & 0x80000000) == 0; log--){
+        buf = (buf << 2) - ((buf << log) >> (log - 1)) + (buf >> 30);
+    }
+
+    LAST_SKIP_BITS(re, gb, 63 - 2*log);
+    CLOSE_READER(re, gb);
+
+    return (signed) (((((buf << log) >> log) - 1) ^ -(buf & 0x1)) + 1) >> 1;
+}
+
 #ifdef TRACE
 
 static inline int get_ue(GetBitContext *s, char *file, char *func, int line){