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 Libav.
8  *
9  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
30 #include "libavutil/intreadwrite.h"
31 #include "parser.h"
32 
33 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
34 
39 typedef struct DiracParseContext {
40  int state;
41  int is_synced;
46  int index;
47  uint8_t *buffer;
49  uint8_t *dirac_unit;
51 
53  const uint8_t *buf, int buf_size)
54 {
55  uint32_t state = pc->state;
56  int i = 0;
57 
58  if (!pc->is_synced) {
59  for (i = 0; i < buf_size; i++) {
60  state = (state << 8) | buf[i];
61  if (state == DIRAC_PARSE_INFO_PREFIX) {
62  state = -1;
63  pc->is_synced = 1;
64  pc->header_bytes_needed = 9;
65  pc->sync_offset = i;
66  break;
67  }
68  }
69  }
70 
71  if (pc->is_synced) {
72  pc->sync_offset = 0;
73  for (; i < buf_size; i++) {
74  if (state == DIRAC_PARSE_INFO_PREFIX) {
75  if ((buf_size-i) >= pc->header_bytes_needed) {
76  pc->state = -1;
77  return i + pc->header_bytes_needed;
78  } else {
79  pc->header_bytes_needed = 9-(buf_size-i);
80  break;
81  }
82  } else
83  state = (state << 8) | buf[i];
84  }
85  }
86  pc->state = state;
87  return -1;
88 }
89 
90 typedef struct DiracParseUnit
91 {
94  uint8_t pu_type;
96 
98  int offset)
99 {
100  uint8_t *start = pc->buffer + offset;
101  uint8_t *end = pc->buffer + pc->index;
102  if (start < pc->buffer || (start+13 > end))
103  return 0;
104  pu->pu_type = start[4];
105 
106  pu->next_pu_offset = AV_RB32(start+5);
107  pu->prev_pu_offset = AV_RB32(start+9);
108 
109  if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
110  pu->next_pu_offset = 13;
111 
112  return 1;
113 }
114 
116  int next, const uint8_t **buf, int *buf_size)
117 {
118  int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
119  s->dts == AV_NOPTS_VALUE);
120  DiracParseContext *pc = s->priv_data;
121 
122  if (pc->overread_index) {
123  memcpy(pc->buffer, pc->buffer + pc->overread_index,
124  pc->index - pc->overread_index);
125  pc->index -= pc->overread_index;
126  pc->overread_index = 0;
127  if (*buf_size == 0 && pc->buffer[4] == 0x10) {
128  *buf = pc->buffer;
129  *buf_size = pc->index;
130  return 0;
131  }
132  }
133 
134  if ( next == -1) {
135  /* Found a possible frame start but not a frame end */
136  void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
137  pc->index + (*buf_size -
138  pc->sync_offset));
139  pc->buffer = new_buffer;
140  memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
141  *buf_size - pc->sync_offset);
142  pc->index += *buf_size - pc->sync_offset;
143  return -1;
144  } else {
145  /* Found a possible frame start and a possible frame end */
146  DiracParseUnit pu1, pu;
147  void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
148  pc->index + next);
149  pc->buffer = new_buffer;
150  memcpy(pc->buffer + pc->index, *buf, next);
151  pc->index += next;
152 
153  /* Need to check if we have a valid Parse Unit. We can't go by the
154  * sync pattern 'BBCD' alone because arithmetic coding of the residual
155  * and motion data can cause the pattern triggering a false start of
156  * frame. So check if the previous parse offset of the next parse unit
157  * is equal to the next parse offset of the current parse unit then
158  * we can be pretty sure that we have a valid parse unit */
159  if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||
160  !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
161  pu.next_pu_offset != pu1.prev_pu_offset) {
162  pc->index -= 9;
163  *buf_size = next-9;
164  pc->header_bytes_needed = 9;
165  return -1;
166  }
167 
168  /* All non-frame data must be accompanied by frame data. This is to
169  * ensure that pts is set correctly. So if the current parse unit is
170  * not frame data, wait for frame data to come along */
171 
172  pc->dirac_unit = pc->buffer + pc->index - 13 -
174 
176 
177  if ((pu.pu_type&0x08) != 0x08) {
178  pc->header_bytes_needed = 9;
179  *buf_size = next;
180  return -1;
181  }
182 
183  /* Get the picture number to set the pts and dts*/
184  if (parse_timing_info) {
185  uint8_t *cur_pu = pc->buffer +
186  pc->index - 13 - pu1.prev_pu_offset;
187  int pts = AV_RB32(cur_pu + 13);
188  if (s->last_pts == 0 && s->last_dts == 0)
189  s->dts = pts - 1;
190  else
191  s->dts = s->last_dts+1;
192  s->pts = pts;
193  if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
194  avctx->has_b_frames = 1;
195  }
196  if (avctx->has_b_frames && s->pts == s->dts)
198 
199  /* Finally have a complete Dirac data unit */
200  *buf = pc->dirac_unit;
201  *buf_size = pc->dirac_unit_size;
202 
203  pc->dirac_unit_size = 0;
204  pc->overread_index = pc->index-13;
205  pc->header_bytes_needed = 9;
206  }
207  return next;
208 }
209 
211  const uint8_t **poutbuf, int *poutbuf_size,
212  const uint8_t *buf, int buf_size)
213 {
214  DiracParseContext *pc = s->priv_data;
215  int next;
216 
217  *poutbuf = NULL;
218  *poutbuf_size = 0;
219 
221  next = buf_size;
222  *poutbuf = buf;
223  *poutbuf_size = buf_size;
224  /* Assume that data has been packetized into an encapsulation unit. */
225  } else {
226  next = find_frame_end(pc, buf, buf_size);
227  if (!pc->is_synced && next == -1) {
228  /* No frame start found yet. So throw away the entire buffer. */
229  return buf_size;
230  }
231 
232  if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
233  return buf_size;
234  }
235  }
236 
237  *poutbuf = buf;
238  *poutbuf_size = buf_size;
239  return next;
240 }
241 
243 {
244  DiracParseContext *pc = s->priv_data;
245 
246  if (pc->buffer_size > 0)
247  av_free(pc->buffer);
248 }
249 
251  .codec_ids = { CODEC_ID_DIRAC },
252  .priv_data_size = sizeof(DiracParseContext),
253  .parser_parse = dirac_parse,
254  .parser_close = dirac_parse_close,
255 };