FFmpeg
vp89_rac.h
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1 /*
2  * Copyright (C) 2006 Aurelien Jacobs <aurel@gnuage.org>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * Range decoder functions common to VP8 and VP9
24  */
25 
26 #ifndef AVCODEC_VP89_RAC_H
27 #define AVCODEC_VP89_RAC_H
28 
29 #include <stdint.h>
30 
31 #include "libavutil/attributes.h"
32 
33 #include "vpx_rac.h"
34 
35 // rounding is different than vpx_rac_get, is vpx_rac_get wrong?
37 {
38  return vpx_rac_get_prob(c, 128);
39 }
40 
42 {
43  int value = 0;
44 
45  while (bits--) {
46  value = (value << 1) | vp89_rac_get(c);
47  }
48 
49  return value;
50 }
51 
52 // how probabilities are associated with decisions is different I think
53 // well, the new scheme fits in the old but this way has one fewer branches per decision
54 static av_always_inline int vp89_rac_get_tree(VPXRangeCoder *c, const int8_t (*tree)[2],
55  const uint8_t *probs)
56 {
57  int i = 0;
58 
59  do {
60  i = tree[i][vpx_rac_get_prob(c, probs[i])];
61  } while (i > 0);
62 
63  return -i;
64 }
65 
66 #endif /* AVCODEC_VP89_RAC_H */
av_unused
#define av_unused
Definition: attributes.h:131
VPXRangeCoder
Definition: vpx_rac.h:35
bits
uint8_t bits
Definition: vp3data.h:141
vp89_rac_get_uint
static av_unused int vp89_rac_get_uint(VPXRangeCoder *c, int bits)
Definition: vp89_rac.h:41
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
attributes.h
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
vpx_rac.h
av_always_inline
#define av_always_inline
Definition: attributes.h:49
value
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default value
Definition: writing_filters.txt:86
vp89_rac_get_tree
static av_always_inline int vp89_rac_get_tree(VPXRangeCoder *c, const int8_t(*tree)[2], const uint8_t *probs)
Definition: vp89_rac.h:54
vp89_rac_get
static av_always_inline int vp89_rac_get(VPXRangeCoder *c)
Definition: vp89_rac.h:36
vpx_rac_get_prob
#define vpx_rac_get_prob
Definition: vpx_rac.h:82