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ffmpeg / libavformat / rtpdec_h263.c @ 45aa9080

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1 45aa9080 Ronald S. Bultje
/*
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 * RTP H.263 Depacketizer, RFC 4629
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 * Copyright (c) 2010 Martin Storsjo
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "avformat.h"
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#include "rtpdec_h263.h"
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#include "libavutil/intreadwrite.h"
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static int h263_handle_packet(AVFormatContext *ctx,
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                              PayloadContext *data,
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                              AVStream *st,
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                              AVPacket * pkt,
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                              uint32_t * timestamp,
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                              const uint8_t * buf,
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                              int len, int flags)
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{
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    uint8_t *ptr;
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    uint16_t header;
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    int startcode, vrc, picture_header;
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    if (len < 2) {
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        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
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        return AVERROR_INVALIDDATA;
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    }
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    /* Decode the 16 bit H.263+ payload header, as described in section
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     * 5.1 of RFC 4629. The fields of this header are:
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     * - 5 reserved bits, should be ignored.
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     * - One bit (P, startcode), indicating a picture start, picture segment
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     *   start or video sequence end. If set, two zero bytes should be
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     *   prepended to the payload.
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     * - One bit (V, vrc), indicating the presence of an 8 bit Video
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     *   Redundancy Coding field after this 16 bit header.
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     * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra
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     *   picture header, following the VRC field.
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     * - 3 bits (PEBIT), the number of bits to ignore of the last byte
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     *   of the extra picture header. (Not used at the moment.)
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     */
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    header = AV_RB16(buf);
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    startcode      = (header & 0x0400) >> 9;
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    vrc            =  header & 0x0200;
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    picture_header = (header & 0x01f8) >> 3;
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    buf += 2;
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    len -= 2;
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    if (vrc) {
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        /* Skip VRC header if present, not used at the moment. */
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        buf += 1;
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        len -= 1;
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    }
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    if (picture_header) {
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        /* Skip extra picture header if present, not used at the moment. */
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        buf += picture_header;
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        len -= picture_header;
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    }
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    if (len < 0) {
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        av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
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        return AVERROR_INVALIDDATA;
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    }
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    if (av_new_packet(pkt, len + startcode)) {
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        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
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        return AVERROR_NOMEM;
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    }
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    pkt->stream_index = st->index;
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    ptr = pkt->data;
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    if (startcode) {
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        *ptr++ = 0;
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        *ptr++ = 0;
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    }
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    memcpy(ptr, buf, len);
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    return 0;
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}
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RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = {
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    .enc_name         = "H263-1998",
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    .codec_type       = CODEC_TYPE_VIDEO,
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    .codec_id         = CODEC_ID_H263,
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    .parse_packet     = h263_handle_packet,
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};
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RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = {
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    .enc_name         = "H263-2000",
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    .codec_type       = CODEC_TYPE_VIDEO,
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    .codec_id         = CODEC_ID_H263,
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    .parse_packet     = h263_handle_packet,
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};