libvpx: Add VP9 decoder.

source/libvpx/vp9/encoder/vp9_boolhuff.h

+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+
+/****************************************************************************
+*
+*   Module Title :     vp9_boolhuff.h
+*
+*   Description  :     Bool Coder header file.
+*
+****************************************************************************/
+#ifndef VP9_ENCODER_VP9_BOOLHUFF_H_
+#define VP9_ENCODER_VP9_BOOLHUFF_H_
+
+#include "vpx_ports/mem.h"
+
+typedef struct {
+  unsigned int lowvalue;
+  unsigned int range;
+  unsigned int value;
+  int count;
+  unsigned int pos;
+  unsigned char *buffer;
+
+  // Variables used to track bit costs without outputing to the bitstream
+  unsigned int  measure_cost;
+  unsigned long bit_counter;
+} BOOL_CODER;
+
+extern void vp9_start_encode(BOOL_CODER *bc, unsigned char *buffer);
+
+extern void vp9_encode_value(BOOL_CODER *br, int data, int bits);
+extern void vp9_encode_unsigned_max(BOOL_CODER *br, int data, int max);
+extern void vp9_stop_encode(BOOL_CODER *bc);
+extern const unsigned int vp9_prob_cost[256];
+
+extern void vp9_encode_uniform(BOOL_CODER *bc, int v, int n);
+extern void vp9_encode_term_subexp(BOOL_CODER *bc, int v, int k, int n);
+extern int vp9_count_uniform(int v, int n);
+extern int vp9_count_term_subexp(int v, int k, int n);
+extern int vp9_recenter_nonneg(int v, int m);
+
+DECLARE_ALIGNED(16, extern const unsigned char, vp9_norm[256]);
+
+
+static void encode_bool(BOOL_CODER *br, int bit, int probability) {
+  unsigned int split;
+  int count = br->count;
+  unsigned int range = br->range;
+  unsigned int lowvalue = br->lowvalue;
+  register unsigned int shift;
+
+#ifdef ENTROPY_STATS
+#if defined(SECTIONBITS_OUTPUT)
+
+  if (bit)
+    Sectionbits[active_section] += vp9_prob_cost[255 - probability];
+  else
+    Sectionbits[active_section] += vp9_prob_cost[probability];
+
+#endif
+#endif
+
+  split = 1 + (((range - 1) * probability) >> 8);
+
+  range = split;
+
+  if (bit) {
+    lowvalue += split;
+    range = br->range - split;
+  }
+
+  shift = vp9_norm[range];
+
+  range <<= shift;
+  count += shift;
+
+  if (count >= 0) {
+    int offset = shift - count;
+
+    if ((lowvalue << (offset - 1)) & 0x80000000) {
+      int x = br->pos - 1;
+
+      while (x >= 0 && br->buffer[x] == 0xff) {
+        br->buffer[x] = (unsigned char)0;
+        x--;
+      }
+
+      br->buffer[x] += 1;
+    }
+
+    br->buffer[br->pos++] = (lowvalue >> (24 - offset));
+    lowvalue <<= offset;
+    shift = count;
+    lowvalue &= 0xffffff;
+    count -= 8;
+  }
+
+  lowvalue <<= shift;
+  br->count = count;
+  br->lowvalue = lowvalue;
+  br->range = range;
+}
+
+#endif