1/*
2 * H.261 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 * H.261 parser
26 */
27
28#include "parser.h"
29
30static int h261_find_frame_end(ParseContext *pc, AVCodecContext *avctx,
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
66static int h261_parse(AVCodecParserContext *s,
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
74    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
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
89const AVCodecParser ff_h261_parser = {
90    .codec_ids      = { AV_CODEC_ID_H261 },
91    .priv_data_size = sizeof(ParseContext),
92    .parser_parse   = h261_parse,
93    .parser_close   = ff_parse_close,
94};
95