127 строки
2.8 KiB
C
127 строки
2.8 KiB
C
/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef __INC_TREEWRITER_H
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#define __INC_TREEWRITER_H
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/* Trees map alphabets into huffman-like codes suitable for an arithmetic
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bit coder. Timothy S Murphy 11 October 2004 */
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#include "vp8/common/treecoder.h"
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#include "boolhuff.h" /* for now */
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typedef BOOL_CODER vp8_writer;
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#define vp8_write vp8_encode_bool
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#define vp8_write_literal vp8_encode_value
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#define vp8_write_bit( W, V) vp8_write( W, V, vp8_prob_half)
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#define vp8bc_write vp8bc_write_bool
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#define vp8bc_write_literal vp8bc_write_bits
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#define vp8bc_write_bit( W, V) vp8bc_write_bits( W, V, 1)
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/* Approximate length of an encoded bool in 256ths of a bit at given prob */
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#define vp8_cost_zero( x) ( vp8_prob_cost[x])
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#define vp8_cost_one( x) vp8_cost_zero( vp8_complement(x))
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#define vp8_cost_bit( x, b) vp8_cost_zero( (b)? vp8_complement(x) : (x) )
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/* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
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/* Both of these return bits, not scaled bits. */
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static unsigned int vp8_cost_branch(const unsigned int ct[2], vp8_prob p)
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{
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/* Imitate existing calculation */
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return ((ct[0] * vp8_cost_zero(p))
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+ (ct[1] * vp8_cost_one(p))) >> 8;
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}
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/* Small functions to write explicit values and tokens, as well as
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estimate their lengths. */
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static void vp8_treed_write
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(
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vp8_writer *const w,
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vp8_tree t,
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const vp8_prob *const p,
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int v,
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int n /* number of bits in v, assumed nonzero */
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)
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{
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vp8_tree_index i = 0;
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do
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{
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const int b = (v >> --n) & 1;
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vp8_write(w, b, p[i>>1]);
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i = t[i+b];
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}
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while (n);
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}
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static void vp8_write_token
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(
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vp8_writer *const w,
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vp8_tree t,
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const vp8_prob *const p,
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vp8_token *const x
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)
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{
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vp8_treed_write(w, t, p, x->value, x->Len);
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}
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static int vp8_treed_cost(
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vp8_tree t,
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const vp8_prob *const p,
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int v,
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int n /* number of bits in v, assumed nonzero */
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)
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{
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int c = 0;
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vp8_tree_index i = 0;
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do
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{
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const int b = (v >> --n) & 1;
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c += vp8_cost_bit(p[i>>1], b);
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i = t[i+b];
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}
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while (n);
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return c;
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}
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static int vp8_cost_token
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(
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vp8_tree t,
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const vp8_prob *const p,
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vp8_token *const x
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)
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{
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return vp8_treed_cost(t, p, x->value, x->Len);
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}
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/* Fill array of costs for all possible token values. */
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void vp8_cost_tokens(
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int *Costs, const vp8_prob *, vp8_tree
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);
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void vp8_cost_tokens2(
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int *Costs, const vp8_prob *, vp8_tree, int
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);
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#endif
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