FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/vc1_parser.c
Date: 2026-01-23 19:11:46
Exec Total Coverage
Lines: 117 130 90.0%
Functions: 3 3 100.0%
Branches: 80 104 76.9%
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1 /*
2 * VC-1 and WMV3 parser
3 * Copyright (c) 2006-2007 Konstantin Shishkov
4 * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /**
24 * @file
25 * VC-1 and WMV3 parser
26 */
27
28 #include "libavutil/attributes.h"
29 #include "libavutil/avassert.h"
30 #include "parser.h"
31 #include "parser_internal.h"
32 #include "vc1.h"
33 #include "get_bits.h"
34 #include "vc1dsp.h"
35
36 /** The maximum number of bytes of a sequence, entry point or
37 * frame header whose values we pay any attention to */
38 #define UNESCAPED_THRESHOLD 37
39
40 /** The maximum number of bytes of a sequence, entry point or
41 * frame header which must be valid memory (because they are
42 * used to update the bitstream cache in skip_bits() calls)
43 */
44 #define UNESCAPED_LIMIT 144
45
46 typedef enum {
47 NO_MATCH,
48 ONE_ZERO,
49 TWO_ZEROS,
50 ONE
51 } VC1ParseSearchState;
52
53 typedef struct VC1ParseContext {
54 ParseContext pc;
55 VC1Context v;
56 uint8_t prev_start_code;
57 size_t bytes_to_skip;
58 uint8_t unesc_buffer[UNESCAPED_LIMIT];
59 size_t unesc_index;
60 VC1ParseSearchState search_state;
61 } VC1ParseContext;
62
63 973 static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
64 const uint8_t *buf, int buf_size)
65 {
66 /* Parse the header we just finished unescaping */
67 973 VC1ParseContext *vpc = s->priv_data;
68 GetBitContext gb;
69 int ret;
70 973 vpc->v.s.avctx = avctx;
71 973 ret = init_get_bits8(&gb, buf, buf_size);
72 av_assert1(ret >= 0); // buf_size is bounded by UNESCAPED_THRESHOLD
73
74
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 973 switch (vpc->prev_start_code) {
75 9 case VC1_CODE_SEQHDR & 0xFF:
76 9 ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
77 9 break;
78 14 case VC1_CODE_ENTRYPOINT & 0xFF:
79 14 ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
80 14 break;
81 305 case VC1_CODE_FRAME & 0xFF:
82
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 305 if(vpc->v.profile < PROFILE_ADVANCED)
83 ✗ ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
84 else
85 305 ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
86
87
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 305 if (ret < 0)
88 ✗ break;
89
90 /* keep AV_PICTURE_TYPE_BI internal to VC1 */
91
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 305 if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
92 ✗ s->pict_type = AV_PICTURE_TYPE_B;
93 else
94 305 s->pict_type = vpc->v.s.pict_type;
95
96
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 305 if (vpc->v.broadcast){
97 // process pulldown flags
98 305 s->repeat_pict = 1;
99 // Pulldown flags are only valid when 'broadcast' has been set.
100
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 305 if (vpc->v.rff){
101 // repeat field
102 ✗ s->repeat_pict = 2;
103
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 305 }else if (vpc->v.rptfrm){
104 // repeat frames
105 ✗ s->repeat_pict = vpc->v.rptfrm * 2 + 1;
106 }
107 }else{
108 ✗ s->repeat_pict = 0;
109 }
110
111
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 305 if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
112
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 44 s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
113 else
114 261 s->field_order = AV_FIELD_PROGRESSIVE;
115
116 305 break;
117 }
118 1946 s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P
119
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 973 : AV_PIX_FMT_NONE;
120
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 973 if (avctx->width && avctx->height) {
121 961 s->width = avctx->width;
122 961 s->height = avctx->height;
123 961 s->coded_width = FFALIGN(avctx->coded_width, 16);
124 961 s->coded_height = FFALIGN(avctx->coded_height, 16);
125 }
126 973 }
127
128 4745 static int vc1_parse(AVCodecParserContext *s,
129 AVCodecContext *avctx,
130 const uint8_t **poutbuf, int *poutbuf_size,
131 const uint8_t *buf, int buf_size)
132 {
133 /* Here we do the searching for frame boundaries and headers at
134 * the same time. Only a minimal amount at the start of each
135 * header is unescaped. */
136 4745 VC1ParseContext *vpc = s->priv_data;
137 4745 int pic_found = vpc->pc.frame_start_found;
138 4745 uint8_t *unesc_buffer = vpc->unesc_buffer;
139 4745 size_t unesc_index = vpc->unesc_index;
140 4745 VC1ParseSearchState search_state = vpc->search_state;
141 4745 int start_code_found = 0;
142 4745 int next = END_NOT_FOUND;
143 4745 int i = vpc->bytes_to_skip;
144
145
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 4745 if (pic_found && buf_size == 0) {
146 /* EOF considered as end of frame */
147 16 memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
148 16 vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
149 16 next = 0;
150 }
151
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 9846 while (i < buf_size) {
152 uint8_t b;
153 5393 start_code_found = 0;
154
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 38288 while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
155 32986 b = buf[i++];
156 32986 unesc_buffer[unesc_index++] = b;
157
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 32986 if (search_state <= ONE_ZERO)
158
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 32765 search_state = b ? NO_MATCH : search_state + 1;
159
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 221 else if (search_state == TWO_ZEROS) {
160
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 130 if (b == 1)
161 91 search_state = ONE;
162
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 39 else if (b > 1) {
163
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 39 if (b == 3)
164 22 unesc_index--; // swallow emulation prevention byte
165 39 search_state = NO_MATCH;
166 }
167 }
168 else { // search_state == ONE
169 // Header unescaping terminates early due to detection of next start code
170 91 search_state = NO_MATCH;
171 91 start_code_found = 1;
172 91 break;
173 }
174 }
175
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 5393 if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
176 ✗ unesc_index >= UNESCAPED_THRESHOLD &&
177 ✗ vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
178 {
179 // No need to keep scanning the rest of the buffer for
180 // start codes if we know it contains a complete frame and
181 // we've already unescaped all we need of the frame header
182 ✗ vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
183 ✗ unesc_index = 0;
184 ✗ break;
185 }
186
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 5393 if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
187
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 57273 while (i < buf_size) {
188
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 52860 if (search_state == NO_MATCH) {
189 27593 i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
190
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 27593 if (i < buf_size) {
191 23222 search_state = ONE_ZERO;
192 }
193 27593 i++;
194 } else {
195 25267 b = buf[i++];
196
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 25267 if (search_state == ONE_ZERO)
197
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 23231 search_state = b ? NO_MATCH : TWO_ZEROS;
198
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 2036 else if (search_state == TWO_ZEROS) {
199
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 1170 if (b >= 1)
200
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 1170 search_state = b == 1 ? ONE : NO_MATCH;
201 }
202 else { // search_state == ONE
203 866 search_state = NO_MATCH;
204 866 start_code_found = 1;
205 866 break;
206 }
207 }
208 }
209 }
210
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 5393 if (start_code_found) {
211 957 vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
212
213 957 vpc->prev_start_code = b;
214 957 unesc_index = 0;
215
216
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 957 if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
217
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 957 if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
218 9 pic_found = 1;
219 }
220
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 948 else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)
221
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 293 && b != (VC1_CODE_ENDOFSEQ & 0xFF)) {
222 292 next = i - 4;
223 292 pic_found = b == (VC1_CODE_FRAME & 0xFF);
224 292 break;
225 }
226 }
227 }
228 }
229
230 4745 vpc->pc.frame_start_found = pic_found;
231 4745 vpc->unesc_index = unesc_index;
232 4745 vpc->search_state = search_state;
233
234
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 4745 if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
235 ✗ next = buf_size;
236 } else {
237
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 4745 if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
238 4437 vpc->bytes_to_skip = 0;
239 4437 *poutbuf = NULL;
240 4437 *poutbuf_size = 0;
241 4437 return buf_size;
242 }
243 }
244
245 /* If we return with a valid pointer to a combined frame buffer
246 * then on the next call then we'll have been unhelpfully rewound
247 * by up to 4 bytes (depending upon whether the start code
248 * overlapped the input buffer, and if so by how much). We don't
249 * want this: it will either cause spurious second detections of
250 * the start code we've already seen, or cause extra bytes to be
251 * inserted at the start of the unescaped buffer. */
252 308 vpc->bytes_to_skip = 4;
253
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 308 if (next < 0 && next != END_NOT_FOUND)
254 ✗ vpc->bytes_to_skip += next;
255
256 308 *poutbuf = buf;
257 308 *poutbuf_size = buf_size;
258 308 return next;
259 }
260
261 8 static av_cold int vc1_parse_init(AVCodecParserContext *s)
262 {
263 8 VC1ParseContext *vpc = s->priv_data;
264 8 vpc->v.s.slice_context_count = 1;
265 8 vpc->v.first_pic_header_flag = 1;
266 8 vpc->v.parse_only = 1;
267 8 vpc->prev_start_code = 0;
268 8 vpc->bytes_to_skip = 0;
269 8 vpc->unesc_index = 0;
270 8 vpc->search_state = NO_MATCH;
271 8 ff_vc1dsp_init(&vpc->v.vc1dsp); /* startcode_find_candidate */
272 8 return 0;
273 }
274
275 const FFCodecParser ff_vc1_parser = {
276 PARSER_CODEC_LIST(AV_CODEC_ID_VC1),
277 .priv_data_size = sizeof(VC1ParseContext),
278 .init = vc1_parse_init,
279 .parse = vc1_parse,
280 .close = ff_parse_close,
281 };
282