shithub: libvpx

ref: e8b818b581b9ab7e9c8f7b1becd753dd4efbdf43
dir: /vp8/encoder/treewriter.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 VPX_VP8_ENCODER_TREEWRITER_H_
#define VPX_VP8_ENCODER_TREEWRITER_H_

/* Trees map alphabets into huffman-like codes suitable for an arithmetic
   bit coder.  Timothy S Murphy  11 October 2004 */

#include "./vpx_config.h"
#include "vp8/common/treecoder.h"

#include "boolhuff.h" /* for now */

#ifdef __cplusplus
extern "C" {
#endif

typedef BOOL_CODER vp8_writer;

#define vp8_write vp8_encode_bool
#define vp8_write_literal vp8_encode_value
#define vp8_write_bit(W, V) vp8_write(W, V, vp8_prob_half)

#define vp8bc_write vp8bc_write_bool
#define vp8bc_write_literal vp8bc_write_bits
#define vp8bc_write_bit(W, V) vp8bc_write_bits(W, V, 1)

/* Approximate length of an encoded bool in 256ths of a bit at given prob */

#define vp8_cost_zero(x) (vp8_prob_cost[x])
#define vp8_cost_one(x) vp8_cost_zero(vp8_complement(x))

#define vp8_cost_bit(x, b) vp8_cost_zero((b) ? vp8_complement(x) : (x))

/* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */

/* Both of these return bits, not scaled bits. */

static INLINE unsigned int vp8_cost_branch(const unsigned int ct[2],
                                           vp8_prob p) {
  /* Imitate existing calculation */

  return ((ct[0] * vp8_cost_zero(p)) + (ct[1] * vp8_cost_one(p))) >> 8;
}

/* Small functions to write explicit values and tokens, as well as
   estimate their lengths. */

static void vp8_treed_write(vp8_writer *const w, vp8_tree t,
                            const vp8_prob *const p, int v,
                            int n) { /* number of bits in v, assumed nonzero */
  vp8_tree_index i = 0;

  do {
    const int b = (v >> --n) & 1;
    vp8_write(w, b, p[i >> 1]);
    i = t[i + b];
  } while (n);
}
static INLINE void vp8_write_token(vp8_writer *const w, vp8_tree t,
                                   const vp8_prob *const p,
                                   vp8_token *const x) {
  vp8_treed_write(w, t, p, x->value, x->Len);
}

static int vp8_treed_cost(vp8_tree t, const vp8_prob *const p, int v,
                          int n) { /* number of bits in v, assumed nonzero */
  int c = 0;
  vp8_tree_index i = 0;

  do {
    const int b = (v >> --n) & 1;
    c += vp8_cost_bit(p[i >> 1], b);
    i = t[i + b];
  } while (n);

  return c;
}
static INLINE int vp8_cost_token(vp8_tree t, const vp8_prob *const p,
                                 vp8_token *const x) {
  return vp8_treed_cost(t, p, x->value, x->Len);
}

/* Fill array of costs for all possible token values. */

void vp8_cost_tokens(int *c, const vp8_prob *, vp8_tree);

void vp8_cost_tokens2(int *c, const vp8_prob *, vp8_tree, int);

#ifdef __cplusplus
}  // extern "C"
#endif

#endif  // VPX_VP8_ENCODER_TREEWRITER_H_