latm_parser.c
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1 /*
2  * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz>
3  *
4  * This file is part of Libav.
5  *
6  * Libav is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * Libav is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with Libav; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
26 #include <stdint.h>
27 #include "parser.h"
28 
29 #define LATM_HEADER 0x56e000 // 0x2b7 (11 bits)
30 #define LATM_MASK 0xFFE000 // top 11 bits
31 #define LATM_SIZE_MASK 0x001FFF // bottom 13 bits
32 
33 typedef struct LATMParseContext{
35  int count;
37 
42 static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf,
43  int buf_size)
44 {
45  LATMParseContext *s = s1->priv_data;
46  ParseContext *pc = &s->pc;
47  int pic_found, i;
48  uint32_t state;
49 
50  pic_found = pc->frame_start_found;
51  state = pc->state;
52 
53  i = 0;
54  if (!pic_found) {
55  for (i = 0; i < buf_size; i++) {
56  state = (state<<8) | buf[i];
57  if ((state & LATM_MASK) == LATM_HEADER) {
58  i++;
59  s->count = -i;
60  pic_found = 1;
61  break;
62  }
63  }
64  }
65 
66  if (pic_found) {
67  /* EOF considered as end of frame */
68  if (buf_size == 0)
69  return 0;
70  if ((state & LATM_SIZE_MASK) - s->count <= buf_size) {
71  pc->frame_start_found = 0;
72  pc->state = -1;
73  return (state & LATM_SIZE_MASK) - s->count;
74  }
75  }
76 
77  s->count += buf_size;
78  pc->frame_start_found = pic_found;
79  pc->state = state;
80 
81  return END_NOT_FOUND;
82 }
83 
85  const uint8_t **poutbuf, int *poutbuf_size,
86  const uint8_t *buf, int buf_size)
87 {
88  LATMParseContext *s = s1->priv_data;
89  ParseContext *pc = &s->pc;
90  int next;
91 
93  next = buf_size;
94  } else {
95  next = latm_find_frame_end(s1, buf, buf_size);
96 
97  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
98  *poutbuf = NULL;
99  *poutbuf_size = 0;
100  return buf_size;
101  }
102  }
103  *poutbuf = buf;
104  *poutbuf_size = buf_size;
105  return next;
106 }
107 
110  .priv_data_size = sizeof(LATMParseContext),
111  .parser_parse = latm_parse,
112  .parser_close = ff_parse_close
113 };