Changeset 296 for libmpc/trunk/libmpcdec/mpc_bits_reader.h

Timestamp:

04/24/07 15:07:19 (17 years ago)

Author:

r2d

Message:

Improved sv8 huffman decoding using canonical property of the huffman tables. It reduces memory usage for the tables and improves speed (mainly with small LUT size).

File:

• libmpc/trunk/libmpcdec/mpc_bits_reader.h (modified) (2 diffs)

libmpc/trunk/libmpcdec/mpc_bits_reader.h

@@ -76 +76 @@
 }
 
+static mpc_inline mpc_int32_t mpc_bits_can_dec(mpc_bits_reader * r, const mpc_can_data *can)
+{
+        mpc_uint16_t code;
+        mpc_huff_lut tmp;
+        const mpc_huffman * Table;
+        code = ((r->buff[0] << 16) | (r->buff[1] << 8) | r->buff[2]) >> r->count;
+
+        tmp = can->lut[code >> (16 - LUT_DEPTH)];
+        if (tmp.Length != 0) {
+                r->buff -= (int)(r->count - tmp.Length) >> 3;
+                r->count = (r->count - tmp.Length) & 0x07;
+                return tmp.Value;
+        }
+
+        Table = can->table + (unsigned char)tmp.Value;
+        while (code < Table->Code) Table++;
+
+        r->buff -= (int)(r->count - Table->Length) >> 3;
+        r->count = (r->count - Table->Length) & 0x07;
+
+        return can->sym[(Table->Value - (code >> (16 - Table->Length))) & 0xFF] ;
+}
+
 // LUT-based huffman decoding routine
 // works with maximum lengths up to 16
@@ -93 +116 @@
 
         Table = lut->table + (unsigned char)tmp.Value;
-
         while (code < Table->Code) Table++;