vp8/encoder/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 :     boolhuff.h
*
*   Description  :     Bool Coder header file.
*
****************************************************************************/
#ifndef __INC_BOOLHUFF_H
#define __INC_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_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 vp8_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