mirror of https://bitbucket.org/ausocean/av.git
88 lines
2.3 KiB
Go
88 lines
2.3 KiB
Go
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/*
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NAME
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rtp.go - provides a data structure intended to encapsulate the properties
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of an rtp packet and also functions to allow manipulation of these packets.
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DESCRIPTION
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See Readme.md
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AUTHOR
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Saxon A. Nelson-Milton <saxon@ausocean.org>
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LICENSE
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rtp.go is Copyright (C) 2018 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with revid in gpl.txt. If not, see [GNU licenses](http://www.gnu.org/licenses).
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*/
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// See https://tools.ietf.org/html/rfc6184 for rtp packet format
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package rtp
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const (
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rtpVer = 2
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defaultHeadSize = 3 * 4 // bytes
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)
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type Pkt struct {
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V byte
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P byte
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X byte
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CC byte
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M byte
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PT byte
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SN int16
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TS int32
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SSRC int32
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Payload []byte
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Padding int
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}
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func (p *Pkt) Bytes() []byte {
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if p.V == 0 {
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p.V = rtpVer
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}
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if p.P != 0 && p.Padding == 0 {
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panic("Padding bit set to something other than 1, but there is no padding size defined!")
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} else if p.P == 0 && p.Padding != 0 {
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panic("Padding bit is set to zero, but it's indicated that there is padding!")
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}
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if p.CC != 0 {
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panic("CC has been set to something other than 0 - this is not supported yet!")
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}
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buf := make([]byte, defaultHeadSize, defaultHeadSize+len(p.Payload)+p.Padding)
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// First 4 bytes
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buf[0] |= p.V<<6 | p.P<<5 | p.CC
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buf[1] |= p.M<<7 | p.PT
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buf[2] |= byte(p.SN >> 8)
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buf[3] |= byte(p.SN)
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// Second lot of 4 bytes
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buf[4] |= byte(p.TS >> 24)
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buf[5] |= byte(p.TS >> 16)
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buf[6] |= byte(p.TS >> 8)
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buf[7] |= byte(p.TS)
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// Third lot of 4 bytes
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buf[8] |= byte(p.SSRC >> 24)
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buf[9] |= byte(p.SSRC >> 16)
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buf[10] |= byte(p.SSRC >> 8)
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buf[11] |= byte(p.SSRC)
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// Add payload and padding
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buf = append(buf, p.Payload...)
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buf = append(buf, append(make([]byte, p.Padding-1, p.Padding), byte(p.Padding))...)
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return buf
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}
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