1/*
2 * RTP H.263 Depacketizer, RFC 4629
3 * Copyright (c) 2010 Martin Storsjo
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include "avformat.h"
23#include "rtpdec_formats.h"
24#include "libavutil/attributes.h"
25#include "libavutil/intreadwrite.h"
26
27static av_cold int h263_init(AVFormatContext *ctx, int st_index,
28                             PayloadContext *data)
29{
30    if (st_index < 0)
31        return 0;
32    ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL;
33    return 0;
34}
35
36int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,
37                          AVStream *st, AVPacket *pkt, uint32_t *timestamp,
38                          const uint8_t *buf, int len, uint16_t seq, int flags)
39{
40    uint8_t *ptr;
41    uint16_t header;
42    int startcode, vrc, picture_header;
43
44    if (len < 2) {
45        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
46        return AVERROR_INVALIDDATA;
47    }
48
49    /* Decode the 16 bit H.263+ payload header, as described in section
50     * 5.1 of RFC 4629. The fields of this header are:
51     * - 5 reserved bits, should be ignored.
52     * - One bit (P, startcode), indicating a picture start, picture segment
53     *   start or video sequence end. If set, two zero bytes should be
54     *   prepended to the payload.
55     * - One bit (V, vrc), indicating the presence of an 8 bit Video
56     *   Redundancy Coding field after this 16 bit header.
57     * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra
58     *   picture header, following the VRC field.
59     * - 3 bits (PEBIT), the number of bits to ignore of the last byte
60     *   of the extra picture header. (Not used at the moment.)
61     */
62    header = AV_RB16(buf);
63    startcode      = (header & 0x0400) >> 9;
64    vrc            =  header & 0x0200;
65    picture_header = (header & 0x01f8) >> 3;
66    buf += 2;
67    len -= 2;
68
69    if (vrc) {
70        /* Skip VRC header if present, not used at the moment. */
71        buf += 1;
72        len -= 1;
73    }
74    if (picture_header) {
75        /* Skip extra picture header if present, not used at the moment. */
76        buf += picture_header;
77        len -= picture_header;
78    }
79
80    if (len < 0) {
81        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
82        return AVERROR_INVALIDDATA;
83    }
84
85    if (av_new_packet(pkt, len + startcode)) {
86        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
87        return AVERROR(ENOMEM);
88    }
89    pkt->stream_index = st->index;
90    ptr = pkt->data;
91
92    if (startcode) {
93        *ptr++ = 0;
94        *ptr++ = 0;
95    }
96    memcpy(ptr, buf, len);
97
98    return 0;
99}
100
101RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = {
102    .enc_name         = "H263-1998",
103    .codec_type       = AVMEDIA_TYPE_VIDEO,
104    .codec_id         = AV_CODEC_ID_H263,
105    .init             = h263_init,
106    .parse_packet     = ff_h263_handle_packet,
107};
108
109RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = {
110    .enc_name         = "H263-2000",
111    .codec_type       = AVMEDIA_TYPE_VIDEO,
112    .codec_id         = AV_CODEC_ID_H263,
113    .init             = h263_init,
114    .parse_packet     = ff_h263_handle_packet,
115};
116