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libavformat
rtpdec_h263.c
Go to the documentation of this file.
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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 Libav.
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*
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* Libav 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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* Libav 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 Libav; 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_formats.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
(ENOMEM);
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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 =
AVMEDIA_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 =
AVMEDIA_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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