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
30
31static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
32    int vop_found, i, j;
33    uint32_t state;
34
35    vop_found= pc->frame_start_found;
36    state= pc->state;
37
38    for(i=0; i<buf_size && !vop_found; i++){
39        state= (state<<8) | buf[i];
40        for(j=0; j<8; j++){
41            if(((state>>j)&0xFFFFF0) == 0x000100){
42                vop_found=1;
43                break;
44            }
45        }
46    }
47    if(vop_found){
48        for(; i<buf_size; i++){
49            state= (state<<8) | buf[i];
50            for(j=0; j<8; j++){
51                if(((state>>j)&0xFFFFF0) == 0x000100){
52                    pc->frame_start_found=0;
53                    pc->state= (state>>(3*8))+0xFF00;
54                    return i-2;
55                }
56            }
57        }
58    }
59
60    pc->frame_start_found= vop_found;
61    pc->state= state;
62    return END_NOT_FOUND;
63}
64
65static int h261_parse(AVCodecParserContext *s,
66                      AVCodecContext *avctx,
67                      const uint8_t **poutbuf, int *poutbuf_size,
68                      const uint8_t *buf, int buf_size)
69{
70    ParseContext *pc = s->priv_data;
71    int next;
72
73    next= h261_find_frame_end(pc,avctx, buf, buf_size);
74    if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
75        *poutbuf = NULL;
76        *poutbuf_size = 0;
77        return buf_size;
78    }
79    *poutbuf = buf;
80    *poutbuf_size = buf_size;
81    return next;
82}
83
84AVCodecParser h261_parser = {
85    { CODEC_ID_H261 },
86    sizeof(ParseContext),
87    NULL,
88    h261_parse,
89    ff_parse_close,
90};
91