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path: root/libavcodec/vc1_parser.c (plain)
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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 "parser.h"
30#include "vc1.h"
31#include "get_bits.h"
32#include "internal.h"
33
34/** The maximum number of bytes of a sequence, entry point or
35 * frame header whose values we pay any attention to */
36#define UNESCAPED_THRESHOLD 37
37
38/** The maximum number of bytes of a sequence, entry point or
39 * frame header which must be valid memory (because they are
40 * used to update the bitstream cache in skip_bits() calls)
41 */
42#define UNESCAPED_LIMIT 144
43
44typedef enum {
45 NO_MATCH,
46 ONE_ZERO,
47 TWO_ZEROS,
48 ONE
49} VC1ParseSearchState;
50
51typedef struct VC1ParseContext {
52 ParseContext pc;
53 VC1Context v;
54 uint8_t prev_start_code;
55 size_t bytes_to_skip;
56 uint8_t unesc_buffer[UNESCAPED_LIMIT];
57 size_t unesc_index;
58 VC1ParseSearchState search_state;
59} VC1ParseContext;
60
61static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
62 const uint8_t *buf, int buf_size)
63{
64 /* Parse the header we just finished unescaping */
65 VC1ParseContext *vpc = s->priv_data;
66 GetBitContext gb;
67 int ret;
68 vpc->v.s.avctx = avctx;
69 vpc->v.parse_only = 1;
70 init_get_bits(&gb, buf, buf_size * 8);
71 switch (vpc->prev_start_code) {
72 case VC1_CODE_SEQHDR & 0xFF:
73 ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
74 break;
75 case VC1_CODE_ENTRYPOINT & 0xFF:
76 ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
77 break;
78 case VC1_CODE_FRAME & 0xFF:
79 if(vpc->v.profile < PROFILE_ADVANCED)
80 ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
81 else
82 ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
83
84 if (ret < 0)
85 break;
86
87 /* keep AV_PICTURE_TYPE_BI internal to VC1 */
88 if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
89 s->pict_type = AV_PICTURE_TYPE_B;
90 else
91 s->pict_type = vpc->v.s.pict_type;
92
93 if (avctx->ticks_per_frame > 1){
94 // process pulldown flags
95 s->repeat_pict = 1;
96 // Pulldown flags are only valid when 'broadcast' has been set.
97 // So ticks_per_frame will be 2
98 if (vpc->v.rff){
99 // repeat field
100 s->repeat_pict = 2;
101 }else if (vpc->v.rptfrm){
102 // repeat frames
103 s->repeat_pict = vpc->v.rptfrm * 2 + 1;
104 }
105 }else{
106 s->repeat_pict = 0;
107 }
108
109 if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
110 s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
111 else
112 s->field_order = AV_FIELD_PROGRESSIVE;
113
114 break;
115 }
116 if (avctx->framerate.num)
117 avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
118 s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P
119 : AV_PIX_FMT_NONE;
120 if (avctx->width && avctx->height) {
121 s->width = avctx->width;
122 s->height = avctx->height;
123 s->coded_width = FFALIGN(avctx->coded_width, 16);
124 s->coded_height = FFALIGN(avctx->coded_height, 16);
125 }
126}
127
128static 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 VC1ParseContext *vpc = s->priv_data;
137 int pic_found = vpc->pc.frame_start_found;
138 uint8_t *unesc_buffer = vpc->unesc_buffer;
139 size_t unesc_index = vpc->unesc_index;
140 VC1ParseSearchState search_state = vpc->search_state;
141 int start_code_found = 0;
142 int next = END_NOT_FOUND;
143 int i = vpc->bytes_to_skip;
144
145 if (pic_found && buf_size == 0) {
146 /* EOF considered as end of frame */
147 memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
148 vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
149 next = 0;
150 }
151 while (i < buf_size) {
152 uint8_t b;
153 start_code_found = 0;
154 while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
155 b = buf[i++];
156 unesc_buffer[unesc_index++] = b;
157 if (search_state <= ONE_ZERO)
158 search_state = b ? NO_MATCH : search_state + 1;
159 else if (search_state == TWO_ZEROS) {
160 if (b == 1)
161 search_state = ONE;
162 else if (b > 1) {
163 if (b == 3)
164 unesc_index--; // swallow emulation prevention byte
165 search_state = NO_MATCH;
166 }
167 }
168 else { // search_state == ONE
169 // Header unescaping terminates early due to detection of next start code
170 search_state = NO_MATCH;
171 start_code_found = 1;
172 break;
173 }
174 }
175 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 break;
184 }
185 if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
186 while (i < buf_size) {
187 if (search_state == NO_MATCH) {
188 i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
189 if (i < buf_size) {
190 search_state = ONE_ZERO;
191 }
192 i++;
193 } else {
194 b = buf[i++];
195 if (search_state == ONE_ZERO)
196 search_state = b ? NO_MATCH : TWO_ZEROS;
197 else if (search_state == TWO_ZEROS) {
198 if (b >= 1)
199 search_state = b == 1 ? ONE : NO_MATCH;
200 }
201 else { // search_state == ONE
202 search_state = NO_MATCH;
203 start_code_found = 1;
204 break;
205 }
206 }
207 }
208 }
209 if (start_code_found) {
210 vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
211
212 vpc->prev_start_code = b;
213 unesc_index = 0;
214
215 if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
216 if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
217 pic_found = 1;
218 }
219 else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
220 next = i - 4;
221 pic_found = b == (VC1_CODE_FRAME & 0xFF);
222 break;
223 }
224 }
225 }
226 }
227
228 vpc->pc.frame_start_found = pic_found;
229 vpc->unesc_index = unesc_index;
230 vpc->search_state = search_state;
231
232 if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
233 next = buf_size;
234 } else {
235 if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
236 vpc->bytes_to_skip = 0;
237 *poutbuf = NULL;
238 *poutbuf_size = 0;
239 return buf_size;
240 }
241 }
242
243 /* If we return with a valid pointer to a combined frame buffer
244 * then on the next call then we'll have been unhelpfully rewound
245 * by up to 4 bytes (depending upon whether the start code
246 * overlapped the input buffer, and if so by how much). We don't
247 * want this: it will either cause spurious second detections of
248 * the start code we've already seen, or cause extra bytes to be
249 * inserted at the start of the unescaped buffer. */
250 vpc->bytes_to_skip = 4;
251 if (next < 0 && next != END_NOT_FOUND)
252 vpc->bytes_to_skip += next;
253
254 *poutbuf = buf;
255 *poutbuf_size = buf_size;
256 return next;
257}
258
259static int vc1_split(AVCodecContext *avctx,
260 const uint8_t *buf, int buf_size)
261{
262 uint32_t state = -1;
263 int charged = 0;
264 const uint8_t *ptr = buf, *end = buf + buf_size;
265
266 while (ptr < end) {
267 ptr = avpriv_find_start_code(ptr, end, &state);
268 if (state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT) {
269 charged = 1;
270 } else if (charged && IS_MARKER(state))
271 return ptr - 4 - buf;
272 }
273
274 return 0;
275}
276
277static av_cold int vc1_parse_init(AVCodecParserContext *s)
278{
279 VC1ParseContext *vpc = s->priv_data;
280 vpc->v.s.slice_context_count = 1;
281 vpc->v.first_pic_header_flag = 1;
282 vpc->prev_start_code = 0;
283 vpc->bytes_to_skip = 0;
284 vpc->unesc_index = 0;
285 vpc->search_state = NO_MATCH;
286 return ff_vc1_init_common(&vpc->v);
287}
288
289AVCodecParser ff_vc1_parser = {
290 .codec_ids = { AV_CODEC_ID_VC1 },
291 .priv_data_size = sizeof(VC1ParseContext),
292 .parser_init = vc1_parse_init,
293 .parser_parse = vc1_parse,
294 .parser_close = ff_parse_close,
295 .split = vc1_split,
296};
297
generated by cgit at 2024-05-17 05:14:01 (GMT)