rtpdec_h263.c 3.4 KB
Newer Older
1 2 3 4
/*
 * RTP H.263 Depacketizer, RFC 4629
 * Copyright (c) 2010 Martin Storsjo
 *
5
 * This file is part of Libav.
6
 *
7
 * Libav is free software; you can redistribute it and/or
8 9 10 11
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
12
 * Libav is distributed in the hope that it will be useful,
13 14 15 16 17
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
18
 * License along with Libav; if not, write to the Free Software
19 20 21 22
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avformat.h"
23
#include "rtpdec_formats.h"
24 25
#include "libavutil/intreadwrite.h"

26 27 28
int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,
                          AVStream *st, AVPacket *pkt, uint32_t *timestamp,
                          const uint8_t *buf, int len, int flags)
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76
{
    uint8_t *ptr;
    uint16_t header;
    int startcode, vrc, picture_header;

    if (len < 2) {
        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
        return AVERROR_INVALIDDATA;
    }

    /* Decode the 16 bit H.263+ payload header, as described in section
     * 5.1 of RFC 4629. The fields of this header are:
     * - 5 reserved bits, should be ignored.
     * - One bit (P, startcode), indicating a picture start, picture segment
     *   start or video sequence end. If set, two zero bytes should be
     *   prepended to the payload.
     * - One bit (V, vrc), indicating the presence of an 8 bit Video
     *   Redundancy Coding field after this 16 bit header.
     * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra
     *   picture header, following the VRC field.
     * - 3 bits (PEBIT), the number of bits to ignore of the last byte
     *   of the extra picture header. (Not used at the moment.)
     */
    header = AV_RB16(buf);
    startcode      = (header & 0x0400) >> 9;
    vrc            =  header & 0x0200;
    picture_header = (header & 0x01f8) >> 3;
    buf += 2;
    len -= 2;

    if (vrc) {
        /* Skip VRC header if present, not used at the moment. */
        buf += 1;
        len -= 1;
    }
    if (picture_header) {
        /* Skip extra picture header if present, not used at the moment. */
        buf += picture_header;
        len -= picture_header;
    }

    if (len < 0) {
        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
        return AVERROR_INVALIDDATA;
    }

    if (av_new_packet(pkt, len + startcode)) {
        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
77
        return AVERROR(ENOMEM);
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92
    }
    pkt->stream_index = st->index;
    ptr = pkt->data;

    if (startcode) {
        *ptr++ = 0;
        *ptr++ = 0;
    }
    memcpy(ptr, buf, len);

    return 0;
}

RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = {
    .enc_name         = "H263-1998",
93
    .codec_type       = AVMEDIA_TYPE_VIDEO,
94
    .codec_id         = AV_CODEC_ID_H263,
95
    .parse_packet     = ff_h263_handle_packet,
96 97 98 99
};

RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = {
    .enc_name         = "H263-2000",
100
    .codec_type       = AVMEDIA_TYPE_VIDEO,
101
    .codec_id         = AV_CODEC_ID_H263,
102
    .parse_packet     = ff_h263_handle_packet,
103
};