FFmpeg
cabac.c
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1 /*
2  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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 #include "libavcodec/cabac.c"
22 
23 #define SIZE 10240
24 
25 #include "libavutil/lfg.h"
26 #include "libavcodec/avcodec.h"
27 #include "libavcodec/put_bits.h"
28 
29 typedef struct CABACTestContext {
34 
35 static inline void put_cabac_bit(CABACTestContext *c, int b)
36 {
37  put_bits(&c->pb, 1, b);
38  for(;c->outstanding_count; c->outstanding_count--){
39  put_bits(&c->pb, 1, 1-b);
40  }
41 }
42 
44 {
45  while (c->dec.range < 0x100) {
46  //FIXME optimize
47  if (c->dec.low < 0x100) {
48  put_cabac_bit(c, 0);
49  } else if (c->dec.low < 0x200) {
50  c->outstanding_count++;
51  c->dec.low -= 0x100;
52  }else{
53  put_cabac_bit(c, 1);
54  c->dec.low -= 0x200;
55  }
56 
57  c->dec.range += c->dec.range;
58  c->dec.low += c->dec.low;
59  }
60 }
61 
62 static void put_cabac(CABACTestContext *c, uint8_t * const state, int bit)
63 {
64  int RangeLPS = ff_h264_lps_range[2 * (c->dec.range & 0xC0) + *state];
65 
66  if(bit == ((*state)&1)){
67  c->dec.range -= RangeLPS;
68  *state = ff_h264_mlps_state[128 + *state];
69  }else{
70  c->dec.low += c->dec.range - RangeLPS;
71  c->dec.range = RangeLPS;
72  *state= ff_h264_mlps_state[127 - *state];
73  }
74 
76 }
77 
78 /**
79  * @param bit 0 -> write zero bit, !=0 write one bit
80  */
82 {
83  c->dec.low += c->dec.low;
84 
85  if(bit){
86  c->dec.low += c->dec.range;
87  }
88 //FIXME optimize
89  if (c->dec.low < 0x200) {
90  put_cabac_bit(c, 0);
91  } else if (c->dec.low < 0x400) {
92  c->outstanding_count++;
93  c->dec.low -= 0x200;
94  }else{
95  put_cabac_bit(c, 1);
96  c->dec.low -= 0x400;
97  }
98 }
99 
100 /**
101  *
102  * @return the number of bytes written
103  */
105 {
106  c->dec.range -= 2;
107 
108  if(!bit){
110  }else{
111  c->dec.low += c->dec.range;
112  c->dec.range = 2;
113 
115 
116  av_assert0(c->dec.low <= 0x1FF);
117  put_cabac_bit(c, c->dec.low >> 9);
118  put_bits(&c->pb, 2, ((c->dec.low >> 7) & 3) | 1);
119 
120  flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
121  }
122 
123  return put_bytes_count(&c->pb, 1);
124 }
125 
126 /**
127  * @param buf_size size of buf in bits
128  */
129 static void init_cabac_encoder(CABACTestContext *c, uint8_t *buf, int buf_size)
130 {
131  init_put_bits(&c->pb, buf, buf_size);
132 
133  c->dec.low = 0;
134  c->dec.range = 0x1FE;
135  c->outstanding_count = 0;
136  c->pb.bit_left++; //avoids firstBitFlag
137 }
138 
139 int main(void){
141  uint8_t b[9*SIZE];
142  uint8_t r[9*SIZE];
143  int i, ret = 0;
144  uint8_t state[10]= {0};
145  AVLFG prng;
146 
147  av_lfg_init(&prng, 1);
148  init_cabac_encoder(&c, b, SIZE);
149 
150  for(i=0; i<SIZE; i++){
151  if(2*i<SIZE) r[i] = av_lfg_get(&prng) % 7;
152  else r[i] = (i>>8)&1;
153  }
154 
155  for(i=0; i<SIZE; i++){
156  put_cabac_bypass(&c, r[i]&1);
157  }
158 
159  for(i=0; i<SIZE; i++){
160  put_cabac(&c, state, r[i]&1);
161  }
162 
163  i= put_cabac_terminate(&c, 1);
164  b[i++] = av_lfg_get(&prng);
165  b[i ] = av_lfg_get(&prng);
166 
167  ff_init_cabac_decoder(&c.dec, b, SIZE);
168 
169  memset(state, 0, sizeof(state));
170 
171  for(i=0; i<SIZE; i++){
172  if ((r[i] & 1) != get_cabac_bypass(&c.dec)) {
173  av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
174  ret = 1;
175  }
176  }
177 
178  for(i=0; i<SIZE; i++){
179  if ((r[i] & 1) != get_cabac_noinline(&c.dec, state)) {
180  av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
181  ret = 1;
182  }
183  }
184  if (!get_cabac_terminate(&c.dec)) {
185  av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
186  ret = 1;
187  }
188 
189  return ret;
190 }
Context structure for the Lagged Fibonacci PRNG.
Definition: lfg.h:33
#define NULL
Definition: coverity.c:32
static void put_bits(Jpeg2000EncoderContext *s, int val, int n)
put n times val bit
Definition: j2kenc.c:218
CABACContext dec
Definition: cabac.c:30
static int put_bytes_count(const PutBitContext *s, int round_up)
Definition: put_bits.h:104
int outstanding_count
Definition: cabac.c:31
static void renorm_cabac_encoder(CABACTestContext *c)
Definition: cabac.c:43
static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t *const state)
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
PutBitContext pb
Definition: cabac.c:32
int main(void)
Definition: cabac.c:139
uint8_t
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
#define SIZE
Definition: cabac.c:23
static int put_cabac_terminate(CABACTestContext *c, int bit)
Definition: cabac.c:104
static struct @321 state
#define av_log(a,...)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:194
const char * r
Definition: vf_curves.c:116
#define b
Definition: input.c:41
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size)
Definition: cabac.c:165
static void put_cabac_bypass(CABACTestContext *c, int bit)
Definition: cabac.c:81
static int av_unused get_cabac_terminate(CABACContext *c)
static void put_cabac_bit(CABACTestContext *c, int b)
Definition: cabac.c:35
Libavcodec external API header.
int bit_left
Definition: put_bits.h:53
static unsigned int av_lfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using an ALFG.
Definition: lfg.h:53
int range
Definition: cabac.h:43
static void put_cabac(CABACTestContext *c, uint8_t *const state, int bit)
Definition: cabac.c:62
av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
Definition: lfg.c:32
static int av_unused get_cabac_bypass(CABACContext *c)
int low
Definition: cabac.h:42
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:147
#define bit(string, value)
Definition: cbs_mpeg2.c:58
static void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
Initialize the PutBitContext s.
Definition: put_bits.h:66
static const uint8_t *const ff_h264_lps_range
Context Adaptive Binary Arithmetic Coder.
static const uint8_t *const ff_h264_mlps_state
int i
Definition: input.c:407
static void init_cabac_encoder(CABACTestContext *c, uint8_t *buf, int buf_size)
Definition: cabac.c:129
bitstream writer API