mirror of
https://github.com/cnotch/ipchub.git
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126 lines
3.6 KiB
Go
126 lines
3.6 KiB
Go
// Copyright (c) 2019,CAOHONGJU All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package rtp
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import (
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"github.com/cnotch/ipchub/av/codec"
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"github.com/cnotch/ipchub/av/codec/aac"
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)
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type aacDepacketizer struct {
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depacketizer
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meta *codec.AudioMeta
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w codec.FrameWriter
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sizeLength int
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indexLength int
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}
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// NewAacDepacketizer 实例化 AAC 解包器
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func NewAacDepacketizer(meta *codec.AudioMeta, w codec.FrameWriter) Depacketizer {
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aacdp := &aacDepacketizer{
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meta: meta,
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w: w,
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sizeLength: 13,
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indexLength: 3,
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}
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aacdp.syncClock.Init(meta.SampleRate)
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return aacdp
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}
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// 以下是当 sizelength=13;indexlength=3;indexdeltalength=3 时
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// Au-header = 13+3 bits(2byte) 的示意图
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | AU-headers-length |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | AU-header(1) |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | AU-header(2) |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | ... |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | AU-header(n) |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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// | pading bits |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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//
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// 当 sizelength=6;indexlength=2;indexdeltalength=2 时
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// 单帧封装时，rtp payload的长度 = AU-header-lengths(两个字节) + AU-header(6+2) + AU的长度
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func (aacdp *aacDepacketizer) Depacketize(packet *Packet) (err error) {
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return aacdp.depacketizeFor2ByteAUHeader(packet)
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}
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func (aacdp *aacDepacketizer) depacketizeFor2ByteAUHeader(packet *Packet) (err error) {
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payload := packet.Payload()
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// AU-headers-length 2bytes
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auHeadersLength := uint16(0) | (uint16(payload[0]) << 8) | uint16(payload[1])
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// AU-headers-length / 16
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auHeadersCount := auHeadersLength >> 4
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// AU 帧数据偏移位置
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framesPayloadOffset := 2 + int(auHeadersCount)<<1
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auHeaders := payload[2:framesPayloadOffset]
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framesPayload := payload[framesPayloadOffset:]
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frameTimeStamp := packet.Timestamp
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for i := 0; i < int(auHeadersCount); i++ {
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auHeader := uint16(0) | (uint16(auHeaders[0]) << 8) | uint16(auHeaders[1])
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frameSize := auHeader >> aacdp.indexLength
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pts := aacdp.rtp2ntp(frameTimeStamp) + ptsDelay
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frame := &codec.Frame{
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MediaType: codec.MediaTypeAudio,
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Dts: pts,
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Pts: pts,
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Payload: framesPayload[:frameSize],
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}
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if err = aacdp.w.WriteFrame(frame); err != nil {
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return
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}
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// 下一帧
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auHeaders = auHeaders[2:]
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framesPayload = framesPayload[frameSize:]
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frameTimeStamp += aac.SamplesPerFrame // 每帧采样数
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}
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return
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}
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func (aacdp *aacDepacketizer) depacketizeFor1ByteAUHeader(packet *Packet) (err error) {
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payload := packet.Payload()
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// AU-headers-length 2bytes
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auHeadersLength := uint16(0) | (uint16(payload[0]) << 8) | uint16(payload[1])
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// AU-headers-length / 16
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auHeadersCount := auHeadersLength >> 4
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// AU 帧数据偏移位置
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framesPayloadOffset := 2 + int(auHeadersCount)
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auHeaders := payload[2:framesPayloadOffset]
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framesPayload := payload[framesPayloadOffset:]
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frameTimeStamp := packet.Timestamp
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for i := 0; i < int(auHeadersCount); i++ {
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auHeader := auHeaders[0]
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frameSize := auHeader >> aacdp.indexLength
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pts := aacdp.rtp2ntp(frameTimeStamp) + ptsDelay
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frame := &codec.Frame{
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MediaType: codec.MediaTypeAudio,
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Dts: pts,
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Pts: pts,
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Payload: framesPayload[:frameSize],
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}
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if err = aacdp.w.WriteFrame(frame); err != nil {
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return
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}
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// 下一帧
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auHeaders = auHeaders[1:]
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framesPayload = framesPayload[frameSize:]
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frameTimeStamp += aac.SamplesPerFrame // 每帧采样数
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}
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return
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}
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