4d0ec7aacd
Add a function clip_pixel() to clip a pixel value to the [0,255] range
of allowed values, and use this where-ever appropriate (e.g. prediction,
reconstruction). Likewise, consistently use the recently added function
clip_prob(), which calculates a binary probability in the [1,255] range.
If possible, try to use get_prob() or its sister get_binary_prob() to
calculate binary probabilities, for consistency.
Since in some places, this means that binary probability calculations
are changed (we use {255,256}*count0/(total) in a range of places,
and all of these are now changed to use 256*count0+(total>>1)/total),
this changes the encoding result, so this patch warrants some extensive
testing.
Change-Id: Ibeeff8d886496839b8e0c0ace9ccc552351f7628
91 lines
2.7 KiB
C
91 lines
2.7 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 VP9_COMMON_VP9_TREECODER_H_
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#define VP9_COMMON_VP9_TREECODER_H_
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#include "vpx/vpx_integer.h"
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typedef unsigned char vp9_prob;
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#define vp9_prob_half ( (vp9_prob) 128)
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typedef signed char vp9_tree_index;
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struct bool_coder_spec;
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typedef struct bool_coder_spec bool_coder_spec;
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typedef struct bool_writer bool_writer;
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typedef struct bool_reader bool_reader;
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typedef const bool_coder_spec c_bool_coder_spec;
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typedef const bool_writer c_bool_writer;
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typedef const bool_reader c_bool_reader;
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# define vp9_complement( x) (255 - x)
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/* We build coding trees compactly in arrays.
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Each node of the tree is a pair of vp9_tree_indices.
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Array index often references a corresponding probability table.
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Index <= 0 means done encoding/decoding and value = -Index,
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Index > 0 means need another bit, specification at index.
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Nonnegative indices are always even; processing begins at node 0. */
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typedef const vp9_tree_index vp9_tree[], *vp9_tree_p;
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typedef const struct vp9_token_struct {
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int value;
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int Len;
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} vp9_token;
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/* Construct encoding array from tree. */
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void vp9_tokens_from_tree(struct vp9_token_struct *, vp9_tree);
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void vp9_tokens_from_tree_offset(struct vp9_token_struct *, vp9_tree,
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int offset);
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/* Convert array of token occurrence counts into a table of probabilities
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for the associated binary encoding tree. Also writes count of branches
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taken for each node on the tree; this facilitiates decisions as to
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probability updates. */
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void vp9_tree_probs_from_distribution(
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int n, /* n = size of alphabet */
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vp9_token tok [ /* n */ ],
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vp9_tree tree,
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vp9_prob probs [ /* n-1 */ ],
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unsigned int branch_ct [ /* n-1 */ ] [2],
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const unsigned int num_events[ /* n */ ]
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);
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static __inline vp9_prob clip_prob(int p) {
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return (p > 255) ? 255u : (p < 1) ? 1u : p;
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}
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static __inline vp9_prob get_prob(int num, int den) {
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return (den == 0) ? 128u : clip_prob((num * 256 + (den >> 1)) / den);
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}
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static __inline vp9_prob get_binary_prob(int n0, int n1) {
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return get_prob(n0, n0 + n1);
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}
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/* this function assumes prob1 and prob2 are already within [1,255] range */
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static __inline vp9_prob weighted_prob(int prob1, int prob2, int factor) {
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return (prob1 * (256 - factor) + prob2 * factor + 128) >> 8;
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}
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#endif
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