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dirac_parser.c
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1 /*
2  * Dirac parser
3  *
4  * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
5  * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
6  *
7  * This file is part of FFmpeg.
8  *
9  * FFmpeg is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * FFmpeg is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 /**
25  * @file
26  * Dirac Parser
27  * @author Marco Gerards <marco@gnu.org>
28  */
29 
30 #include <string.h>
31 
32 #include "libavutil/intreadwrite.h"
33 #include "libavutil/mem.h"
34 
35 #include "parser.h"
36 
37 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
38 
39 /**
40  * Find the end of the current frame in the bitstream.
41  * @return the position of the first byte of the next frame or -1
42  */
43 typedef struct DiracParseContext {
44  int state;
45  int is_synced;
50  int index;
55 
57  const uint8_t *buf, int buf_size)
58 {
59  uint32_t state = pc->state;
60  int i = 0;
61 
62  if (!pc->is_synced) {
63  for (i = 0; i < buf_size; i++) {
64  state = (state << 8) | buf[i];
65  if (state == DIRAC_PARSE_INFO_PREFIX) {
66  state = -1;
67  pc->is_synced = 1;
68  pc->header_bytes_needed = 9;
69  pc->sync_offset = i;
70  break;
71  }
72  }
73  }
74 
75  if (pc->is_synced) {
76  pc->sync_offset = 0;
77  for (; i < buf_size; i++) {
78  if (state == DIRAC_PARSE_INFO_PREFIX) {
79  if ((buf_size - i) >= pc->header_bytes_needed) {
80  pc->state = -1;
81  return i + pc->header_bytes_needed;
82  } else {
83  pc->header_bytes_needed = 9 - (buf_size - i);
84  break;
85  }
86  } else
87  state = (state << 8) | buf[i];
88  }
89  }
90  pc->state = state;
91  return -1;
92 }
93 
94 typedef struct DiracParseUnit {
99 
101  int offset)
102 {
103  uint8_t *start = pc->buffer + offset;
104  uint8_t *end = pc->buffer + pc->index;
105  if (start < pc->buffer || (start + 13 > end))
106  return 0;
107  pu->pu_type = start[4];
108 
109  pu->next_pu_offset = AV_RB32(start + 5);
110  pu->prev_pu_offset = AV_RB32(start + 9);
111 
112  if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
113  pu->next_pu_offset = 13;
114 
115  return 1;
116 }
117 
119  int next, const uint8_t **buf, int *buf_size)
120 {
121  int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
122  s->dts == AV_NOPTS_VALUE);
123  DiracParseContext *pc = s->priv_data;
124 
125  if (pc->overread_index) {
126  memcpy(pc->buffer, pc->buffer + pc->overread_index,
127  pc->index - pc->overread_index);
128  pc->index -= pc->overread_index;
129  pc->overread_index = 0;
130  if (*buf_size == 0 && pc->buffer[4] == 0x10) {
131  *buf = pc->buffer;
132  *buf_size = pc->index;
133  return 0;
134  }
135  }
136 
137  if (next == -1) {
138  /* Found a possible frame start but not a frame end */
139  void *new_buffer =
141  pc->index + (*buf_size - pc->sync_offset));
142  pc->buffer = new_buffer;
143  memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset),
144  *buf_size - pc->sync_offset);
145  pc->index += *buf_size - pc->sync_offset;
146  return -1;
147  } else {
148  /* Found a possible frame start and a possible frame end */
149  DiracParseUnit pu1, pu;
150  void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
151  pc->index + next);
152  pc->buffer = new_buffer;
153  memcpy(pc->buffer + pc->index, *buf, next);
154  pc->index += next;
155 
156  /* Need to check if we have a valid Parse Unit. We can't go by the
157  * sync pattern 'BBCD' alone because arithmetic coding of the residual
158  * and motion data can cause the pattern triggering a false start of
159  * frame. So check if the previous parse offset of the next parse unit
160  * is equal to the next parse offset of the current parse unit then
161  * we can be pretty sure that we have a valid parse unit */
162  if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||
163  !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
164  pu.next_pu_offset != pu1.prev_pu_offset ||
165  pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset
166  ) {
167  pc->index -= 9;
168  *buf_size = next - 9;
169  pc->header_bytes_needed = 9;
170  return -1;
171  }
172 
173  /* All non-frame data must be accompanied by frame data. This is to
174  * ensure that pts is set correctly. So if the current parse unit is
175  * not frame data, wait for frame data to come along */
176 
177  pc->dirac_unit = pc->buffer + pc->index - 13 -
179 
181 
182  if ((pu.pu_type & 0x08) != 0x08) {
183  pc->header_bytes_needed = 9;
184  *buf_size = next;
185  return -1;
186  }
187 
188  /* Get the picture number to set the pts and dts*/
189  if (parse_timing_info) {
190  uint8_t *cur_pu = pc->buffer +
191  pc->index - 13 - pu1.prev_pu_offset;
192  int pts = AV_RB32(cur_pu + 13);
193  if (s->last_pts == 0 && s->last_dts == 0)
194  s->dts = pts - 1;
195  else
196  s->dts = s->last_dts + 1;
197  s->pts = pts;
198  if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
199  avctx->has_b_frames = 1;
200  }
201  if (avctx->has_b_frames && s->pts == s->dts)
203 
204  /* Finally have a complete Dirac data unit */
205  *buf = pc->dirac_unit;
206  *buf_size = pc->dirac_unit_size;
207 
208  pc->dirac_unit_size = 0;
209  pc->overread_index = pc->index - 13;
210  pc->header_bytes_needed = 9;
211  }
212  return next;
213 }
214 
216  const uint8_t **poutbuf, int *poutbuf_size,
217  const uint8_t *buf, int buf_size)
218 {
219  DiracParseContext *pc = s->priv_data;
220  int next;
221 
222  *poutbuf = NULL;
223  *poutbuf_size = 0;
224 
226  next = buf_size;
227  *poutbuf = buf;
228  *poutbuf_size = buf_size;
229  /* Assume that data has been packetized into an encapsulation unit. */
230  } else {
231  next = find_frame_end(pc, buf, buf_size);
232  if (!pc->is_synced && next == -1)
233  /* No frame start found yet. So throw away the entire buffer. */
234  return buf_size;
235 
236  if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0)
237  return buf_size;
238  }
239 
240  *poutbuf = buf;
241  *poutbuf_size = buf_size;
242  return next;
243 }
244 
246 {
247  DiracParseContext *pc = s->priv_data;
248 
249  if (pc->buffer_size > 0)
250  av_free(pc->buffer);
251 }
252 
255  .priv_data_size = sizeof(DiracParseContext),
256  .parser_parse = dirac_parse,
257  .parser_close = dirac_parse_close,
258 };