/*

 * RTP H.263 Depacketizer, RFC 4629

 * Copyright (c) 2010 Martin Storsjo

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * 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.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * 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

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "avformat.h"

#include "rtpdec_formats.h"

#include "libavutil/attributes.h"

#include "libavutil/intreadwrite.h"

int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,

                          AVStream *st, AVPacket *pkt, uint32_t *timestamp,

                          const uint8_t *buf, int len, uint16_t seq, int flags)

{

    uint8_t *ptr;

    uint16_t header;

    int startcode, vrc, picture_header, ret;

    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 ((ret = av_new_packet(pkt, len + startcode)) < 0) {

        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");

        return ret;

    }

    pkt->stream_index = st->index;

    ptr = pkt->data;

    if (startcode) {

        *ptr++ = 0;

        *ptr++ = 0;

    }

    memcpy(ptr, buf, len);

    return 0;

}

const RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = {

    .enc_name         = "H263-1998",

    .codec_type       = AVMEDIA_TYPE_VIDEO,

    .codec_id         = AV_CODEC_ID_H263,

    .need_parsing     = AVSTREAM_PARSE_FULL,

    .parse_packet     = ff_h263_handle_packet,

};

const RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = {

    .enc_name         = "H263-2000",

    .codec_type       = AVMEDIA_TYPE_VIDEO,

    .codec_id         = AV_CODEC_ID_H263,

    .need_parsing     = AVSTREAM_PARSE_FULL,

    .parse_packet     = ff_h263_handle_packet,

};