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h261_parser.c
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1 /*
2  * H261 parser
3  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4  * Copyright (c) 2004 Maarten Daniels
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  * h261codec.
26  */
27 
28 #include "parser.h"
29 
31  const uint8_t *buf, int buf_size)
32 {
33  int vop_found, i, j;
34  uint32_t state;
35 
36  vop_found = pc->frame_start_found;
37  state = pc->state;
38 
39  for (i = 0; i < buf_size && !vop_found; i++) {
40  state = (state << 8) | buf[i];
41  for (j = 0; j < 8; j++) {
42  if (((state >> j) & 0xFFFFF0) == 0x000100) {
43  vop_found = 1;
44  break;
45  }
46  }
47  }
48  if (vop_found) {
49  for (; i < buf_size; i++) {
50  state = (state << 8) | buf[i];
51  for (j = 0; j < 8; j++) {
52  if (((state >> j) & 0xFFFFF0) == 0x000100) {
53  pc->frame_start_found = 0;
54  pc->state = (state >> (3 * 8)) + 0xFF00;
55  return i - 2;
56  }
57  }
58  }
59  }
60 
61  pc->frame_start_found = vop_found;
62  pc->state = state;
63  return END_NOT_FOUND;
64 }
65 
67  AVCodecContext *avctx,
68  const uint8_t **poutbuf, int *poutbuf_size,
69  const uint8_t *buf, int buf_size)
70 {
71  ParseContext *pc = s->priv_data;
72  int next;
73 
75  next = buf_size;
76  } else {
77  next = h261_find_frame_end(pc, avctx, buf, buf_size);
78  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
79  *poutbuf = NULL;
80  *poutbuf_size = 0;
81  return buf_size;
82  }
83  }
84  *poutbuf = buf;
85  *poutbuf_size = buf_size;
86  return next;
87 }
88 
91  .priv_data_size = sizeof(ParseContext),
92  .parser_parse = h261_parse,
93  .parser_close = ff_parse_close,
94 };
AVCodecParser ff_h261_parser
Definition: h261_parser.c:89
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:631
int codec_ids[5]
Definition: avcodec.h:4719
int frame_start_found
Definition: parser.h:34
uint8_t
static int h261_find_frame_end(ParseContext *pc, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
Definition: h261_parser.c:30
int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size)
Combine the (truncated) bitstream to a complete frame.
Definition: parser.c:231
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:4574
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:307
static struct @197 state
main external API structure.
Definition: avcodec.h:1502
void * buf
Definition: avisynth_c.h:553
uint32_t state
contains the last few bytes in MSB order
Definition: parser.h:33
#define END_NOT_FOUND
Definition: parser.h:40
static int h261_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: h261_parser.c:66