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vc1_parser.c
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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 
33 /** The maximum number of bytes of a sequence, entry point or
34  * frame header whose values we pay any attention to */
35 #define UNESCAPED_THRESHOLD 37
36 
37 /** The maximum number of bytes of a sequence, entry point or
38  * frame header which must be valid memory (because they are
39  * used to update the bitstream cache in skip_bits() calls)
40  */
41 #define UNESCAPED_LIMIT 144
42 
43 typedef enum {
49 
50 typedef struct {
54  size_t bytes_to_skip;
55  uint8_t unesc_buffer[UNESCAPED_LIMIT];
56  size_t unesc_index;
59 
61  const uint8_t *buf, int buf_size)
62 {
63  /* Parse the header we just finished unescaping */
64  VC1ParseContext *vpc = s->priv_data;
65  GetBitContext gb;
66  int ret;
67  vpc->v.s.avctx = avctx;
68  vpc->v.parse_only = 1;
69  init_get_bits(&gb, buf, buf_size * 8);
70  switch (vpc->prev_start_code) {
71  case VC1_CODE_SEQHDR & 0xFF:
72  ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
73  break;
74  case VC1_CODE_ENTRYPOINT & 0xFF:
75  ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
76  break;
77  case VC1_CODE_FRAME & 0xFF:
78  if(vpc->v.profile < PROFILE_ADVANCED)
79  ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
80  else
81  ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
82 
83  if (ret < 0)
84  break;
85 
86  /* keep AV_PICTURE_TYPE_BI internal to VC1 */
87  if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
89  else
90  s->pict_type = vpc->v.s.pict_type;
91 
92  if (avctx->ticks_per_frame > 1){
93  // process pulldown flags
94  s->repeat_pict = 1;
95  // Pulldown flags are only valid when 'broadcast' has been set.
96  // So ticks_per_frame will be 2
97  if (vpc->v.rff){
98  // repeat field
99  s->repeat_pict = 2;
100  }else if (vpc->v.rptfrm){
101  // repeat frames
102  s->repeat_pict = vpc->v.rptfrm * 2 + 1;
103  }
104  }else{
105  s->repeat_pict = 0;
106  }
107 
108  if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
109  s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
110  else
112 
113  break;
114  }
115  if (avctx->framerate.num)
116  avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
117 }
118 
120  AVCodecContext *avctx,
121  const uint8_t **poutbuf, int *poutbuf_size,
122  const uint8_t *buf, int buf_size)
123 {
124  /* Here we do the searching for frame boundaries and headers at
125  * the same time. Only a minimal amount at the start of each
126  * header is unescaped. */
127  VC1ParseContext *vpc = s->priv_data;
128  int pic_found = vpc->pc.frame_start_found;
129  uint8_t *unesc_buffer = vpc->unesc_buffer;
130  size_t unesc_index = vpc->unesc_index;
131  VC1ParseSearchState search_state = vpc->search_state;
132  int start_code_found = 0;
133  int next = END_NOT_FOUND;
134  int i = vpc->bytes_to_skip;
135 
136  if (pic_found && buf_size == 0) {
137  /* EOF considered as end of frame */
138  memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
139  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
140  next = 0;
141  }
142  while (i < buf_size) {
143  uint8_t b;
144  start_code_found = 0;
145  while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
146  b = buf[i++];
147  unesc_buffer[unesc_index++] = b;
148  if (search_state <= ONE_ZERO)
149  search_state = b ? NO_MATCH : search_state + 1;
150  else if (search_state == TWO_ZEROS) {
151  if (b == 1)
152  search_state = ONE;
153  else if (b > 1) {
154  if (b == 3)
155  unesc_index--; // swallow emulation prevention byte
156  search_state = NO_MATCH;
157  }
158  }
159  else { // search_state == ONE
160  // Header unescaping terminates early due to detection of next start code
161  search_state = NO_MATCH;
162  start_code_found = 1;
163  break;
164  }
165  }
166  if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
167  unesc_index >= UNESCAPED_THRESHOLD &&
168  vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
169  {
170  // No need to keep scanning the rest of the buffer for
171  // start codes if we know it contains a complete frame and
172  // we've already unescaped all we need of the frame header
173  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
174  break;
175  }
176  if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
177  while (i < buf_size) {
178  if (search_state == NO_MATCH) {
179  i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
180  if (i < buf_size) {
181  search_state = ONE_ZERO;
182  }
183  i++;
184  } else {
185  b = buf[i++];
186  if (search_state == ONE_ZERO)
187  search_state = b ? NO_MATCH : TWO_ZEROS;
188  else if (search_state == TWO_ZEROS) {
189  if (b >= 1)
190  search_state = b == 1 ? ONE : NO_MATCH;
191  }
192  else { // search_state == ONE
193  search_state = NO_MATCH;
194  start_code_found = 1;
195  break;
196  }
197  }
198  }
199  }
200  if (start_code_found) {
201  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
202 
203  vpc->prev_start_code = b;
204  unesc_index = 0;
205 
206  if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
207  if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
208  pic_found = 1;
209  }
210  else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
211  next = i - 4;
212  pic_found = b == (VC1_CODE_FRAME & 0xFF);
213  break;
214  }
215  }
216  }
217  }
218 
219  vpc->pc.frame_start_found = pic_found;
220  vpc->unesc_index = unesc_index;
221  vpc->search_state = search_state;
222 
224  next = buf_size;
225  } else {
226  if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
227  vpc->bytes_to_skip = 0;
228  *poutbuf = NULL;
229  *poutbuf_size = 0;
230  return buf_size;
231  }
232  }
233 
234  /* If we return with a valid pointer to a combined frame buffer
235  * then on the next call then we'll have been unhelpfully rewound
236  * by up to 4 bytes (depending upon whether the start code
237  * overlapped the input buffer, and if so by how much). We don't
238  * want this: it will either cause spurious second detections of
239  * the start code we've already seen, or cause extra bytes to be
240  * inserted at the start of the unescaped buffer. */
241  vpc->bytes_to_skip = 4;
242  if (next < 0 && next != END_NOT_FOUND)
243  vpc->bytes_to_skip += next;
244 
245  *poutbuf = buf;
246  *poutbuf_size = buf_size;
247  return next;
248 }
249 
250 static int vc1_split(AVCodecContext *avctx,
251  const uint8_t *buf, int buf_size)
252 {
253  int i;
254  uint32_t state= -1;
255  int charged=0;
256 
257  for(i=0; i<buf_size; i++){
258  state= (state<<8) | buf[i];
259  if(IS_MARKER(state)){
260  if(state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT){
261  charged=1;
262  }else if(charged){
263  return i-3;
264  }
265  }
266  }
267  return 0;
268 }
269 
271 {
272  VC1ParseContext *vpc = s->priv_data;
273  vpc->v.s.slice_context_count = 1;
274  vpc->v.first_pic_header_flag = 1;
275  vpc->prev_start_code = 0;
276  vpc->bytes_to_skip = 0;
277  vpc->unesc_index = 0;
278  vpc->search_state = NO_MATCH;
279  return ff_vc1_init_common(&vpc->v);
280 }
281 
283  .codec_ids = { AV_CODEC_ID_VC1 },
284  .priv_data_size = sizeof(VC1ParseContext),
285  .parser_init = vc1_parse_init,
286  .parser_parse = vc1_parse,
287  .parser_close = ff_parse_close,
288  .split = vc1_split,
289 };