vp9_writer.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.
 */

#ifndef VP9_ENCODER_VP9_WRITER_H_
#define VP9_ENCODER_VP9_WRITER_H_

#include "vpx_ports/mem.h"

#include "vp9/common/vp9_prob.h"

#ifdef __cplusplus
extern "C" {
#endif

typedef struct {
  unsigned int lowvalue;
  unsigned int range;
  unsigned int value;
  int count;
  unsigned int pos;
  uint8_t *buffer;

  // Variables used to track bit costs without outputing to the bitstream
  unsigned int  measure_cost;
  uint64_t bit_counter;
} vp9_writer;

void vp9_start_encode(vp9_writer *bc, uint8_t *buffer);
void vp9_stop_encode(vp9_writer *bc);

static void vp9_write(vp9_writer *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;

  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] = 0;
        x--;
      }

      br->buffer[x] += 1;