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Currently, AVStream contains an embedded AVCodecContext instance, which
is used by demuxers to export stream parameters to the caller and by
muxers to receive stream parameters from the caller. It is also used
internally as the codec context that is passed to parsers.
In addition, it is also widely used by the callers as the decoding (when
demuxer) or encoding (when muxing) context, though this has been
officially discouraged since Libav 11.
There are multiple important problems with this approach:
- the fields in AVCodecContext are in general one of
* stream parameters
* codec options
* codec state
However, it's not clear which ones are which. It is consequently
unclear which fields are a demuxer allowed to set or a muxer allowed to
read. This leads to erratic behaviour depending on whether decoding or
encoding is being performed or not (and whether it uses the AVStream
embedded codec context).
- various synchronization issues arising from the fact that the same
context is used by several different APIs (muxers/demuxers,
parsers, bitstream filters and encoders/decoders) simultaneously, with
there being no clear rules for who can modify what and the different
processes being typically delayed with respect to each other.
- avformat_find_stream_info() making it necessary to support opening
and closing a single codec context multiple times, thus
complicating the semantics of freeing various allocated objects in the
codec context.
Those problems are resolved by replacing the AVStream embedded codec
context with a newly added AVCodecParameters instance, which stores only
the stream parameters exported by the demuxers or read by the muxers.
116 lines
3.9 KiB
C
116 lines
3.9 KiB
C
/*
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* RTP definitions
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* Copyright (c) 2002 Fabrice Bellard
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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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#ifndef AVFORMAT_RTP_H
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#define AVFORMAT_RTP_H
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#include "libavformat/avformat.h"
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#include "libavcodec/avcodec.h"
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#include "libavutil/mathematics.h"
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/**
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* Return the payload type for a given stream used in the given format context.
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* Static payload types are derived from the codec.
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* Dynamic payload type are derived from the id field in AVStream.
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* The format context private option payload_type overrides both.
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*
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* @param fmt The context of the format
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* @param par The codec parameters
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* @param idx The stream index
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* @return The payload type (the 'PT' field in the RTP header).
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*/
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int ff_rtp_get_payload_type(AVFormatContext *fmt, AVCodecParameters *par,
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int idx);
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/**
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* Initialize a codec context based on the payload type.
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*
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* Fill the codec_type and codec_id fields of a codec context with
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* information depending on the payload type; for audio codecs, the
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* channels and sample_rate fields are also filled.
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*
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* @param par The codec parameters
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* @param payload_type The payload type (the 'PT' field in the RTP header)
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* @return In case of unknown payload type or dynamic payload type, a
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* negative value is returned; otherwise, 0 is returned
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*/
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int ff_rtp_get_codec_info(AVCodecParameters *par, int payload_type);
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/**
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* Return the encoding name (as defined in
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* http://www.iana.org/assignments/rtp-parameters) for a given payload type.
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*
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* @param payload_type The payload type (the 'PT' field in the RTP header)
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* @return In case of unknown payload type or dynamic payload type, a pointer
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* to an empty string is returned; otherwise, a pointer to a string containing
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* the encoding name is returned
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*/
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const char *ff_rtp_enc_name(int payload_type);
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/**
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* Return the codec id for the given encoding name and codec type.
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*
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* @param buf A pointer to the string containing the encoding name
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* @param codec_type The codec type
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* @return In case of unknown encoding name, AV_CODEC_ID_NONE is returned;
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* otherwise, the codec id is returned
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*/
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enum AVCodecID ff_rtp_codec_id(const char *buf, enum AVMediaType codec_type);
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#define RTP_PT_PRIVATE 96
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#define RTP_VERSION 2
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#define RTP_MAX_SDES 256 /**< maximum text length for SDES */
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/* RTCP packets use 0.5% of the bandwidth */
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#define RTCP_TX_RATIO_NUM 5
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#define RTCP_TX_RATIO_DEN 1000
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/* An arbitrary id value for RTP Xiph streams - only relevant to indicate
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* that the configuration has changed within a stream (by changing the
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* ident value sent).
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*/
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#define RTP_XIPH_IDENT 0xfecdba
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/* RTCP packet types */
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enum RTCPType {
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RTCP_FIR = 192,
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RTCP_NACK, // 193
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RTCP_SMPTETC,// 194
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RTCP_IJ, // 195
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RTCP_SR = 200,
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RTCP_RR, // 201
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RTCP_SDES, // 202
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RTCP_BYE, // 203
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RTCP_APP, // 204
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RTCP_RTPFB,// 205
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RTCP_PSFB, // 206
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RTCP_XR, // 207
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RTCP_AVB, // 208
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RTCP_RSI, // 209
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RTCP_TOKEN,// 210
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};
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#define RTP_PT_IS_RTCP(x) (((x) >= RTCP_FIR && (x) <= RTCP_IJ) || \
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((x) >= RTCP_SR && (x) <= RTCP_TOKEN))
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#define NTP_TO_RTP_FORMAT(x) av_rescale((x), INT64_C(1) << 32, 1000000)
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#endif /* AVFORMAT_RTP_H */
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