Changeset 290 for libmpc/branches/r2d/libmpcdec/mpc_bits_reader.h

Timestamp:

04/23/07 16:47:30 (17 years ago)

Author:

r2d

Message:

improved decoder speed using LUT for huffman decoding. profiling/bench needed (see LUT_DEPTH parameter in huffman.h)

File:

• libmpc/branches/r2d/libmpcdec/mpc_bits_reader.h (modified) (2 diffs)

libmpc/branches/r2d/libmpcdec/mpc_bits_reader.h

@@ -61 +61 @@
 }
 
-// FIXME : this must be implemented with a lookup table
 // basic huffman decoding routine
 // works with maximum lengths up to 16
@@ -68 +67 @@
         mpc_uint16_t code;
         code = ((r->buff[0] << 16) | (r->buff[1] << 8) | r->buff[2]) >> r->count;
+
+        while (code < Table->Code) Table++;
+
+        r->buff -= (int)(r->count - Table->Length) >> 3;
+        r->count = (r->count - Table->Length) & 0x07;
+
+        return Table->Value;
+}
+
+// LUT-based huffman decoding routine
+// works with maximum lengths up to 16
+static mpc_inline mpc_int32_t mpc_bits_huff_lut(mpc_bits_reader * r, const mpc_lut_data *lut)
+{
+        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 = lut->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 = lut->table + (unsigned char)tmp.Value;
 
         while (code < Table->Code) Table++;