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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 }
116 
118  AVCodecContext *avctx,
119  const uint8_t **poutbuf, int *poutbuf_size,
120  const uint8_t *buf, int buf_size)
121 {
122  /* Here we do the searching for frame boundaries and headers at
123  * the same time. Only a minimal amount at the start of each
124  * header is unescaped. */
125  VC1ParseContext *vpc = s->priv_data;
126  int pic_found = vpc->pc.frame_start_found;
127  uint8_t *unesc_buffer = vpc->unesc_buffer;
128  size_t unesc_index = vpc->unesc_index;
129  VC1ParseSearchState search_state = vpc->search_state;
130  int start_code_found;
131  int next = END_NOT_FOUND;
132  int i = vpc->bytes_to_skip;
133 
134  if (pic_found && buf_size == 0) {
135  /* EOF considered as end of frame */
136  memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
137  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
138  next = 0;
139  }
140  while (i < buf_size) {
141  uint8_t b;
142  start_code_found = 0;
143  while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
144  b = buf[i++];
145  unesc_buffer[unesc_index++] = b;
146  if (search_state <= ONE_ZERO)
147  search_state = b ? NO_MATCH : search_state + 1;
148  else if (search_state == TWO_ZEROS) {
149  if (b == 1)
150  search_state = ONE;
151  else if (b > 1) {
152  if (b == 3)
153  unesc_index--; // swallow emulation prevention byte
154  search_state = NO_MATCH;
155  }
156  }
157  else { // search_state == ONE
158  // Header unescaping terminates early due to detection of next start code
159  search_state = NO_MATCH;
160  start_code_found = 1;
161  break;
162  }
163  }
164  if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
165  unesc_index >= UNESCAPED_THRESHOLD &&
166  vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
167  {
168  // No need to keep scanning the rest of the buffer for
169  // start codes if we know it contains a complete frame and
170  // we've already unescaped all we need of the frame header
171  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
172  break;
173  }
174  if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
175  while (i < buf_size) {
176  if (search_state == NO_MATCH) {
177  i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
178  if (i < buf_size) {
179  search_state = ONE_ZERO;
180  }
181  i++;
182  } else {
183  b = buf[i++];
184  if (search_state == ONE_ZERO)
185  search_state = b ? NO_MATCH : TWO_ZEROS;
186  else if (search_state == TWO_ZEROS) {
187  if (b >= 1)
188  search_state = b == 1 ? ONE : NO_MATCH;
189  }
190  else { // search_state == ONE
191  search_state = NO_MATCH;
192  start_code_found = 1;
193  break;
194  }
195  }
196  }
197  }
198  if (start_code_found) {
199  vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
200 
201  vpc->prev_start_code = b;
202  unesc_index = 0;
203 
204  if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
205  if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
206  pic_found = 1;
207  }
208  else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
209  next = i - 4;
210  pic_found = b == (VC1_CODE_FRAME & 0xFF);
211  break;
212  }
213  }
214  }
215  }
216 
217  vpc->pc.frame_start_found = pic_found;
218  vpc->unesc_index = unesc_index;
219  vpc->search_state = search_state;
220 
222  next = buf_size;
223  } else {
224  if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
225  vpc->bytes_to_skip = 0;
226  *poutbuf = NULL;
227  *poutbuf_size = 0;
228  return buf_size;
229  }
230  }
231 
232  /* If we return with a valid pointer to a combined frame buffer
233  * then on the next call then we'll have been unhelpfully rewound
234  * by up to 4 bytes (depending upon whether the start code
235  * overlapped the input buffer, and if so by how much). We don't
236  * want this: it will either cause spurious second detections of
237  * the start code we've already seen, or cause extra bytes to be
238  * inserted at the start of the unescaped buffer. */
239  vpc->bytes_to_skip = 4;
240  if (next < 0 && next != END_NOT_FOUND)
241  vpc->bytes_to_skip += next;
242 
243  *poutbuf = buf;
244  *poutbuf_size = buf_size;
245  return next;
246 }
247 
248 static int vc1_split(AVCodecContext *avctx,
249  const uint8_t *buf, int buf_size)
250 {
251  int i;
252  uint32_t state= -1;
253  int charged=0;
254 
255  for(i=0; i<buf_size; i++){
256  state= (state<<8) | buf[i];
257  if(IS_MARKER(state)){
258  if(state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT){
259  charged=1;
260  }else if(charged){
261  return i-3;
262  }
263  }
264  }
265  return 0;
266 }
267 
269 {
270  VC1ParseContext *vpc = s->priv_data;
271  vpc->v.s.slice_context_count = 1;
272  vpc->v.first_pic_header_flag = 1;
273  vpc->prev_start_code = 0;
274  vpc->bytes_to_skip = 0;
275  vpc->unesc_index = 0;
276  vpc->search_state = NO_MATCH;
277  return ff_vc1_init_common(&vpc->v);
278 }
279 
281  .codec_ids = { AV_CODEC_ID_VC1 },
282  .priv_data_size = sizeof(VC1ParseContext),
283  .parser_init = vc1_parse_init,
284  .parser_parse = vc1_parse,
285  .parser_close = ff_parse_close,
286  .split = vc1_split,
287 };