FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavcodec/dirac_arith.h
Date: 2021-09-16 08:47:15
Exec Total Coverage
Lines: 50 54 92.6%
Branches: 14 16 87.5%

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1 /*
2 * Copyright (C) 2007 Marco Gerards <marco@gnu.org>
3 * Copyright (C) 2009 David Conrad
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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 * Arithmetic decoder for Dirac
25 * @author Marco Gerards <marco@gnu.org>
26 */
27
28 #ifndef AVCODEC_DIRAC_ARITH_H
29 #define AVCODEC_DIRAC_ARITH_H
30
31 #include "libavutil/x86/asm.h"
32 #include "bytestream.h"
33 #include "get_bits.h"
34
35 enum dirac_arith_contexts {
36 CTX_ZPZN_F1,
37 CTX_ZPNN_F1,
38 CTX_NPZN_F1,
39 CTX_NPNN_F1,
40 CTX_ZP_F2,
41 CTX_ZP_F3,
42 CTX_ZP_F4,
43 CTX_ZP_F5,
44 CTX_ZP_F6,
45 CTX_NP_F2,
46 CTX_NP_F3,
47 CTX_NP_F4,
48 CTX_NP_F5,
49 CTX_NP_F6,
50 CTX_COEFF_DATA,
51 CTX_SIGN_NEG,
52 CTX_SIGN_ZERO,
53 CTX_SIGN_POS,
54 CTX_ZERO_BLOCK,
55 CTX_DELTA_Q_F,
56 CTX_DELTA_Q_DATA,
57 CTX_DELTA_Q_SIGN,
58
59 DIRAC_CTX_COUNT
60 };
61
62 // Dirac resets the arith decoder between decoding various types of data,
63 // so many contexts are never used simultaneously. Thus, we can reduce
64 // the number of contexts needed by reusing them.
65 #define CTX_SB_F1 CTX_ZP_F5
66 #define CTX_SB_DATA 0
67 #define CTX_PMODE_REF1 0
68 #define CTX_PMODE_REF2 1
69 #define CTX_GLOBAL_BLOCK 2
70 #define CTX_MV_F1 CTX_ZP_F2
71 #define CTX_MV_DATA 0
72 #define CTX_DC_F1 CTX_ZP_F5
73 #define CTX_DC_DATA 0
74
75 typedef struct {
76 unsigned low;
77 uint16_t range;
78 int16_t counter;
79
80 const uint8_t *bytestream;
81 const uint8_t *bytestream_end;
82
83 uint16_t contexts[DIRAC_CTX_COUNT];
84 int error;
85 int overread;
86 } DiracArith;
87
88 extern const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT];
89 extern int16_t ff_dirac_prob_branchless[256][2];
90
91 1024041 static inline void renorm(DiracArith *c)
92 {
93 #if HAVE_FAST_CLZ
94 1024041 int shift = 14 - av_log2_16bit(c->range-1) + ((c->range-1)>>15);
95
96 1024041 c->low <<= shift;
97 1024041 c->range <<= shift;
98 1024041 c->counter += shift;
99 #else
100 while (c->range <= 0x4000) {
101 c->low <<= 1;
102 c->range <<= 1;
103 c->counter++;
104 }
105 #endif
106 1024041 }
107
108 1024041 static inline void refill(DiracArith *c)
109 {
110 1024041 int counter = c->counter;
111
112
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1024041 if (counter >= 0) {
113 46510 int new = bytestream_get_be16(&c->bytestream);
114
115 // the spec defines overread bits to be 1, and streams rely on this
116
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46510 if (c->bytestream > c->bytestream_end) {
117 495 new |= 0xff;
118
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495 if (c->bytestream > c->bytestream_end+1)
119 91 new |= 0xff00;
120
121 495 c->bytestream = c->bytestream_end;
122 495 c->overread ++;
123
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495 if (c->overread > 4)
124 c->error = AVERROR_INVALIDDATA;
125 }
126
127 46510 c->low += new << counter;
128 46510 counter -= 16;
129 }
130 1024041 c->counter = counter;
131 1024041 }
132
133 1024041 static inline int dirac_get_arith_bit(DiracArith *c, int ctx)
134 {
135 1024041 int prob_zero = c->contexts[ctx];
136 int range_times_prob, bit;
137 1024041 unsigned low = c->low;
138 1024041 int range = c->range;
139
140 1024041 range_times_prob = (c->range * prob_zero) >> 16;
141
142 #if ARCH_X86 && HAVE_FAST_CMOV && HAVE_INLINE_ASM && HAVE_6REGS
143 1024041 low -= range_times_prob << 16;
144 1024041 range -= range_times_prob;
145 1024041 bit = 0;
146 1024041 __asm__(
147 "cmpl %5, %4 \n\t"
148 "setae %b0 \n\t"
149 "cmovb %3, %2 \n\t"
150 "cmovb %5, %1 \n\t"
151 : "+q"(bit), "+r"(range), "+r"(low)
152 1024041 : "r"(c->low), "r"(c->low>>16),
153 "r"(range_times_prob)
154 );
155 #else
156 bit = (low >> 16) >= range_times_prob;
157 if (bit) {
158 low -= range_times_prob << 16;
159 range -= range_times_prob;
160 } else {
161 range = range_times_prob;
162 }
163 #endif
164
165 1024041 c->contexts[ctx] += ff_dirac_prob_branchless[prob_zero>>8][bit];
166 1024041 c->low = low;
167 1024041 c->range = range;
168
169 1024041 renorm(c);
170 1024041 refill(c);
171 1024041 return bit;
172 }
173
174 353584 static inline int dirac_get_arith_uint(DiracArith *c, int follow_ctx, int data_ctx)
175 {
176 353584 int ret = 1;
177
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573506 while (!dirac_get_arith_bit(c, follow_ctx)) {
178
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219922 if (ret >= 0x40000000) {
179 av_log(NULL, AV_LOG_ERROR, "dirac_get_arith_uint overflow\n");
180 c->error = AVERROR_INVALIDDATA;
181 return -1;
182 }
183 219922 ret <<= 1;
184 219922 ret += dirac_get_arith_bit(c, data_ctx);
185 219922 follow_ctx = ff_dirac_next_ctx[follow_ctx];
186 }
187 353584 return ret-1;
188 }
189
190 14164 static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ctx)
191 {
192 14164 int ret = dirac_get_arith_uint(c, follow_ctx, data_ctx);
193
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14164 if (ret && dirac_get_arith_bit(c, data_ctx+1))
194 1346 ret = -ret;
195 14164 return ret;
196 }
197
198 void ff_dirac_init_arith_tables(void);
199 void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length);
200
201 #endif /* AVCODEC_DIRAC_ARITH_H */
202