1/*
2 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file
24 * Context Adaptive Binary Arithmetic Coder.
25 */
26
27#include <string.h>
28
29#include "libavutil/common.h"
30#include "get_bits.h"
31#include "cabac.h"
32#include "cabac_functions.h"
33
34static const uint8_t lps_range[64][4]= {
35{128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
36{116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
37{ 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
38{ 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
39{ 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
40{ 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
41{ 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
42{ 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
43{ 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
44{ 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
45{ 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
46{ 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
47{ 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
48{ 10, 12, 14, 16}, {  9, 11, 13, 15}, {  9, 11, 12, 14}, {  8, 10, 12, 14},
49{  8,  9, 11, 13}, {  7,  9, 11, 12}, {  7,  9, 10, 12}, {  7,  8, 10, 11},
50{  6,  8,  9, 11}, {  6,  7,  9, 10}, {  6,  7,  8,  9}, {  2,  2,  2,  2},
51};
52
53uint8_t ff_h264_mlps_state[4*64];
54uint8_t ff_h264_lps_range[4*2*64];
55static uint8_t h264_mps_state[2 * 64];
56
57static const uint8_t mps_state[64]= {
58  1, 2, 3, 4, 5, 6, 7, 8,
59  9,10,11,12,13,14,15,16,
60 17,18,19,20,21,22,23,24,
61 25,26,27,28,29,30,31,32,
62 33,34,35,36,37,38,39,40,
63 41,42,43,44,45,46,47,48,
64 49,50,51,52,53,54,55,56,
65 57,58,59,60,61,62,62,63,
66};
67
68static const uint8_t lps_state[64]= {
69  0, 0, 1, 2, 2, 4, 4, 5,
70  6, 7, 8, 9, 9,11,11,12,
71 13,13,15,15,16,16,18,18,
72 19,19,21,21,22,22,23,24,
73 24,25,26,26,27,27,28,29,
74 29,30,30,30,31,32,32,33,
75 33,33,34,34,35,35,35,36,
76 36,36,37,37,37,38,38,63,
77};
78
79const uint8_t ff_h264_norm_shift[512]= {
80 9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
81 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
82 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
83 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
84 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
85 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
86 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
87 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
88 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
89 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
90 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
91 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
92 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
93 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
94 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
95 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
96 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
97 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
98 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
99 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
100};
101
102/**
103 *
104 * @param buf_size size of buf in bits
105 */
106void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
107    init_put_bits(&c->pb, buf, buf_size);
108
109    c->low= 0;
110    c->range= 0x1FE;
111    c->outstanding_count= 0;
112    c->pb.bit_left++; //avoids firstBitFlag
113}
114
115/**
116 *
117 * @param buf_size size of buf in bits
118 */
119void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
120    c->bytestream_start=
121    c->bytestream= buf;
122    c->bytestream_end= buf + buf_size;
123
124#if CABAC_BITS == 16
125    c->low =  (*c->bytestream++)<<18;
126    c->low+=  (*c->bytestream++)<<10;
127#else
128    c->low =  (*c->bytestream++)<<10;
129#endif
130    c->low+= ((*c->bytestream++)<<2) + 2;
131    c->range= 0x1FE;
132}
133
134void ff_init_cabac_states(CABACContext *c){
135    int i, j;
136
137    for(i=0; i<64; i++){
138        for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
139            ff_h264_lps_range[j*2*64+2*i+0]=
140            ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
141        }
142
143        ff_h264_mlps_state[128+2*i+0]=
144        h264_mps_state[2 * i + 0] = 2 * mps_state[i] + 0;
145        ff_h264_mlps_state[128+2*i+1]=
146        h264_mps_state[2 * i + 1] = 2 * mps_state[i] + 1;
147
148        if( i ){
149            ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
150            ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
151        }else{
152            ff_h264_mlps_state[128-2*i-1]= 1;
153            ff_h264_mlps_state[128-2*i-2]= 0;
154        }
155    }
156}
157
158#ifdef TEST
159#define SIZE 10240
160
161#include "libavutil/lfg.h"
162#include "avcodec.h"
163#include "cabac.h"
164
165static inline void put_cabac_bit(CABACContext *c, int b){
166    put_bits(&c->pb, 1, b);
167    for(;c->outstanding_count; c->outstanding_count--){
168        put_bits(&c->pb, 1, 1-b);
169    }
170}
171
172static inline void renorm_cabac_encoder(CABACContext *c){
173    while(c->range < 0x100){
174        //FIXME optimize
175        if(c->low<0x100){
176            put_cabac_bit(c, 0);
177        }else if(c->low<0x200){
178            c->outstanding_count++;
179            c->low -= 0x100;
180        }else{
181            put_cabac_bit(c, 1);
182            c->low -= 0x200;
183        }
184
185        c->range+= c->range;
186        c->low += c->low;
187    }
188}
189
190static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
191    int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + *state];
192
193    if(bit == ((*state)&1)){
194        c->range -= RangeLPS;
195        *state    = h264_mps_state[*state];
196    }else{
197        c->low += c->range - RangeLPS;
198        c->range = RangeLPS;
199    }
200
201    renorm_cabac_encoder(c);
202}
203
204/**
205 * @param bit 0 -> write zero bit, !=0 write one bit
206 */
207static void put_cabac_bypass(CABACContext *c, int bit){
208    c->low += c->low;
209
210    if(bit){
211        c->low += c->range;
212    }
213//FIXME optimize
214    if(c->low<0x200){
215        put_cabac_bit(c, 0);
216    }else if(c->low<0x400){
217        c->outstanding_count++;
218        c->low -= 0x200;
219    }else{
220        put_cabac_bit(c, 1);
221        c->low -= 0x400;
222    }
223}
224
225/**
226 *
227 * @return the number of bytes written
228 */
229static int put_cabac_terminate(CABACContext *c, int bit){
230    c->range -= 2;
231
232    if(!bit){
233        renorm_cabac_encoder(c);
234    }else{
235        c->low += c->range;
236        c->range= 2;
237
238        renorm_cabac_encoder(c);
239
240        assert(c->low <= 0x1FF);
241        put_cabac_bit(c, c->low>>9);
242        put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
243
244        flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
245    }
246
247    return (put_bits_count(&c->pb)+7)>>3;
248}
249
250int main(void){
251    CABACContext c;
252    uint8_t b[9*SIZE];
253    uint8_t r[9*SIZE];
254    int i;
255    uint8_t state[10]= {0};
256    AVLFG prng;
257
258    av_lfg_init(&prng, 1);
259    ff_init_cabac_encoder(&c, b, SIZE);
260    ff_init_cabac_states(&c);
261
262    for(i=0; i<SIZE; i++){
263        r[i] = av_lfg_get(&prng) % 7;
264    }
265
266    for(i=0; i<SIZE; i++){
267START_TIMER
268        put_cabac_bypass(&c, r[i]&1);
269STOP_TIMER("put_cabac_bypass")
270    }
271
272    for(i=0; i<SIZE; i++){
273START_TIMER
274        put_cabac(&c, state, r[i]&1);
275STOP_TIMER("put_cabac")
276    }
277
278    put_cabac_terminate(&c, 1);
279
280    ff_init_cabac_decoder(&c, b, SIZE);
281
282    memset(state, 0, sizeof(state));
283
284    for(i=0; i<SIZE; i++){
285START_TIMER
286        if( (r[i]&1) != get_cabac_bypass(&c) )
287            av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
288STOP_TIMER("get_cabac_bypass")
289    }
290
291    for(i=0; i<SIZE; i++){
292START_TIMER
293        if( (r[i]&1) != get_cabac(&c, state) )
294            av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
295STOP_TIMER("get_cabac")
296    }
297    if(!get_cabac_terminate(&c))
298        av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
299
300    return 0;
301}
302
303#endif /* TEST */
304