FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/mpegvideo_parser.c
Date: 2025-07-28 20:30:09
Exec Total Coverage
Lines: 155 162 95.7%
Functions: 4 4 100.0%
Branches: 108 131 82.4%
Line Branch Exec Source
1 /*
2 * MPEG-1 / MPEG-2 video parser
3 * Copyright (c) 2000,2001 Fabrice Bellard
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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 #include "libavutil/avassert.h"
24 #include "decode.h"
25 #include "parser.h"
26 #include "mpeg12.h"
27 #include "mpeg12data.h"
28 #include "startcode.h"
29
30 struct MpvParseContext {
31 ParseContext pc;
32 AVRational frame_rate;
33 int progressive_sequence;
34 int width, height;
35 };
36
37 /**
38 * Find the end of the current frame in the bitstream.
39 * @return the position of the first byte of the next frame, or -1
40 */
41 54549 static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
42 int buf_size, AVCodecParserContext *s)
43 {
44 int i;
45 54549 uint32_t state = pc->state;
46
47 /* EOF considered as end of frame */
48
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 54549 if (buf_size == 0)
49 347 return 0;
50
51 /*
52 0 frame start -> 1/4
53 1 first_SEQEXT -> 0/2
54 2 first field start -> 3/0
55 3 second_SEQEXT -> 2/0
56 4 searching end
57 */
58
59
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 309104 for (i = 0; i < buf_size; i++) {
60 av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
61
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 261492 if (pc->frame_start_found & 1) {
62
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 26746 if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
63 2719 pc->frame_start_found--;
64
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 24027 else if (state == EXT_START_CODE + 2) {
65
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 8009 if ((buf[i] & 3) == 3)
66 4145 pc->frame_start_found = 0;
67 else
68 3864 pc->frame_start_found = (pc->frame_start_found + 1) & 3;
69 }
70 26746 state++;
71 } else {
72 234746 i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
73
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 234746 if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
74 7036 i++;
75 7036 pc->frame_start_found = 4;
76 }
77
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 234746 if (state == SEQ_END_CODE) {
78 11 pc->frame_start_found = 0;
79 11 pc->state = -1;
80 11 return i + 1;
81 }
82
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 234735 if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
83 ✗ pc->frame_start_found = 0;
84
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 234735 if (pc->frame_start_found < 4 && state == EXT_START_CODE)
85 10728 pc->frame_start_found++;
86
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 234735 if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
87
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 136849 if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
88 6579 pc->frame_start_found = 0;
89 6579 pc->state = -1;
90 6579 return i - 3;
91 }
92 }
93
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 228156 if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
94 7013 ff_fetch_timestamp(s, i - 3, 1, i > 3);
95 }
96 }
97 }
98 47612 pc->state = state;
99 47612 return END_NOT_FOUND;
100 }
101
102 9644 static void mpegvideo_extract_headers(AVCodecParserContext *s,
103 AVCodecContext *avctx,
104 const uint8_t *buf, int buf_size)
105 {
106 9644 struct MpvParseContext *pc = s->priv_data;
107 9644 const uint8_t *buf_end = buf + buf_size;
108 int bytes_left;
109 9644 int did_set_size=0;
110 9644 int set_dim_ret = 0;
111 9644 int bit_rate = 0;
112 9644 int vbv_delay = 0;
113 9644 enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
114
115 // number of picture coding extensions (i.e. MPEG2 pictures)
116 // in this packet - should be 1 or 2
117 9644 int nb_pic_ext = 0;
118 // when there are two pictures in the packet this indicates
119 // which field is in the first of them
120 9644 int first_field = AV_FIELD_UNKNOWN;
121
122 //FIXME replace the crap with get_bits()
123
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 35690 while (buf < buf_end) {
124 35417 uint32_t start_code = -1;
125 35417 buf= avpriv_find_start_code(buf, buf_end, &start_code);
126 35417 bytes_left = buf_end - buf;
127
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 35417 switch(start_code) {
128 9344 case PICTURE_START_CODE:
129
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 9344 if (bytes_left >= 2) {
130 9344 s->pict_type = (buf[1] >> 3) & 7;
131
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 9344 if (bytes_left >= 4)
132 9344 vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
133 }
134 9344 break;
135 1980 case SEQ_START_CODE:
136
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 1980 if (bytes_left >= 7) {
137 int frame_rate_index;
138
139 1980 pc->width = (buf[0] << 4) | (buf[1] >> 4);
140 1980 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
141
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 1980 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
142 282 set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
143 282 did_set_size=1;
144 }
145 1980 pix_fmt = AV_PIX_FMT_YUV420P;
146 1980 frame_rate_index = buf[3] & 0xf;
147 1980 pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
148 1980 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
149 1980 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
150 }
151 1980 break;
152 11423 case EXT_START_CODE:
153
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 11423 if (bytes_left >= 1) {
154
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 11423 switch (buf[0] >> 4) { // ext_type
155 1841 case 0x1: /* sequence extension */
156
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 1841 if (bytes_left >= 6) {
157 1841 int horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
158 1841 int vert_size_ext = (buf[2] >> 5) & 3;
159 1841 int bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
160 1841 int frame_rate_ext_n = (buf[5] >> 5) & 3;
161 1841 int frame_rate_ext_d = (buf[5] & 0x1f);
162 1841 pc->progressive_sequence = buf[1] & (1 << 3);
163 1841 avctx->has_b_frames= !(buf[5] >> 7);
164
165
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 1841 switch ((buf[1] >> 1) & 3) { // chroma_format
166 786 case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
167 1055 case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
168 ✗ case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
169 }
170
171 1841 pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
172 1841 pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
173 1841 bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
174
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 1841 if(did_set_size)
175 263 set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
176 1841 avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
177 1841 avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
178 1841 avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
179 }
180 1841 break;
181 8472 case 0x8: /* picture coding extension */
182
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 8472 if (bytes_left >= 5) {
183 8472 int top_field_first = buf[3] & (1 << 7);
184 8472 int repeat_first_field = buf[3] & (1 << 1);
185 8472 int progressive_frame = buf[4] & (1 << 7);
186
187 /* check if we must repeat the frame */
188 8472 s->repeat_pict = 1;
189
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 8472 if (repeat_first_field) {
190
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 9 if (pc->progressive_sequence) {
191 ✗ if (top_field_first)
192 ✗ s->repeat_pict = 5;
193 else
194 ✗ s->repeat_pict = 3;
195
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 9 } else if (progressive_frame) {
196 9 s->repeat_pict = 2;
197 }
198 }
199
200
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 8472 if (!pc->progressive_sequence && !progressive_frame) {
201
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 5385 if (top_field_first)
202 1873 s->field_order = AV_FIELD_TT;
203 else
204 3512 s->field_order = AV_FIELD_BB;
205 } else
206 3087 s->field_order = AV_FIELD_PROGRESSIVE;
207
208 8472 s->picture_structure = buf[2] & 3;
209
210
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 8472 if (!nb_pic_ext) {
211 // remember parity of the first field for the case
212 // when there are 2 fields in packet
213
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 8472 switch (s->picture_structure) {
214 1939 case AV_PICTURE_STRUCTURE_BOTTOM_FIELD: first_field = AV_FIELD_BB; break;
215 6 case AV_PICTURE_STRUCTURE_TOP_FIELD: first_field = AV_FIELD_TT; break;
216 }
217 }
218
219 8472 nb_pic_ext++;
220 }
221 8472 break;
222 }
223 }
224 11423 break;
225 ✗ case -1:
226 9371 goto the_end;
227 12670 default:
228 /* we stop parsing when we encounter a slice. It ensures
229 that this function takes a negligible amount of time */
230
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 12670 if (start_code >= SLICE_MIN_START_CODE &&
231
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 12670 start_code <= SLICE_MAX_START_CODE)
232 9371 goto the_end;
233 3299 break;
234 }
235 }
236 273 the_end:
237
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 9644 if (set_dim_ret < 0)
238 ✗ av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
239
240
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 9644 if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate && bit_rate != 0x3FFFF) {
241 1163 avctx->rc_max_rate = 400LL*bit_rate;
242 }
243
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 9644 if (bit_rate &&
244
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 1980 ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
245 1065 avctx->bit_rate = 400LL*bit_rate;
246 }
247
248
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 9644 if (pix_fmt != AV_PIX_FMT_NONE) {
249 1980 s->format = pix_fmt;
250 1980 s->width = pc->width;
251 1980 s->height = pc->height;
252 1980 s->coded_width = FFALIGN(pc->width, 16);
253 1980 s->coded_height = FFALIGN(pc->height, 16);
254 }
255
256
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 9644 if (avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO || nb_pic_ext > 1) {
257 902 s->repeat_pict = 1;
258 902 s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
259
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 902 s->field_order = nb_pic_ext > 1 ? first_field : AV_FIELD_PROGRESSIVE;
260 }
261 9644 }
262
263 57256 static int mpegvideo_parse(AVCodecParserContext *s,
264 AVCodecContext *avctx,
265 const uint8_t **poutbuf, int *poutbuf_size,
266 const uint8_t *buf, int buf_size)
267 {
268 57256 struct MpvParseContext *pc1 = s->priv_data;
269 57256 ParseContext *pc= &pc1->pc;
270 int next;
271
272
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 57256 if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
273 2707 next= buf_size;
274 }else{
275 54549 next = mpeg1_find_frame_end(pc, buf, buf_size, s);
276
277
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 54549 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
278 47612 *poutbuf = NULL;
279 47612 *poutbuf_size = 0;
280 47612 return buf_size;
281 }
282
283 }
284 /* we have a full frame : we just parse the first few MPEG headers
285 to have the full timing information. The time take by this
286 function should be negligible for uncorrupted streams */
287 9644 mpegvideo_extract_headers(s, avctx, buf, buf_size);
288 ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
289 s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
290
291 9644 *poutbuf = buf;
292 9644 *poutbuf_size = buf_size;
293 9644 return next;
294 }
295
296 679 static int mpegvideo_parse_init(AVCodecParserContext *s)
297 {
298 679 s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
299 679 return 0;
300 }
301
302 const AVCodecParser ff_mpegvideo_parser = {
303 .codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
304 .priv_data_size = sizeof(struct MpvParseContext),
305 .parser_init = mpegvideo_parse_init,
306 .parser_parse = mpegvideo_parse,
307 .parser_close = ff_parse_close,
308 };
309