109 lines
3.5 KiB
C
109 lines
3.5 KiB
C
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/*
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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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};
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