mirror of https://bitbucket.org/ausocean/av.git
257 lines
6.9 KiB
Go
257 lines
6.9 KiB
Go
/*
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NAME
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FLVGenerator.go
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DESCRIPTION
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See Readme.md
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AUTHOR
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Saxon Nelson-Milton <saxon@ausocean.org>
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LICENSE
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FLVGenerator.go is Copyright (C) 2017 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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package generator
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import (
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"bitbucket.org/ausocean/av/flv"
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//"../flv"
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_ "fmt"
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"time"
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)
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const (
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inputChanLength = 500
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outputChanLength = 500
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audioSize = 18
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videoHeaderSize = 16
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interFrameCode = 1
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keyFrameCode = 5
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sequenceCode = 6
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)
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// Data representing silent audio (required for youtube)
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var dummyAudioTag1Data = []byte{0x00, 0x12, 0x08, 0x56, 0xe5, 0x00}
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var dummyAudioTag2Data = []byte{0x01, 0xdc, 0x00, 0x4c, 0x61, 0x76, 0x63, 0x35,
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0x38, 0x2e, 0x36, 0x2e, 0x31, 0x30, 0x32, 0x00, 0x02, 0x30, 0x40, 0x0e}
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// flvGenerator provides properties required for the generation of flv video
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// from raw video data
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type flvGenerator struct {
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fps uint
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inputChan chan []byte
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outputChan chan []byte
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audioFlag bool
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videoFlag bool
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lastTagSize int
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header flv.Header
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startTime time.Time
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firstTag bool
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isGenerating bool
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}
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// GetInputChan returns the input channel to the generator. This is where the
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// raw data frames are entered into the generator
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func (g *flvGenerator) GetInputChan() chan []byte {
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return g.inputChan
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}
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// GetOutputChan retuns the output chan of the generator - this is where the
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// flv packets (more specifically tags) are outputted.
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func (g *flvGenerator) GetOutputChan() chan []byte {
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return g.outputChan
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}
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// NewFlvGenerator retuns an instance of the flvGenerator struct
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func NewFlvGenerator(audio bool, video bool, fps uint) (g *flvGenerator) {
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g = new(flvGenerator)
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g.fps = fps
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g.audioFlag = audio
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g.videoFlag = video
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g.lastTagSize = 0
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g.inputChan = make(chan []byte, inputChanLength)
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g.outputChan = make(chan []byte, outputChanLength)
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g.firstTag = true
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g.isGenerating = false
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return
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}
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// Start begins the generation routine - i.e. if raw data is given to the input
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// channel flv tags will be produced and available from the output channel.
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func (g *flvGenerator) Start() {
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g.isGenerating = true;
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go g.generate()
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}
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func (g *flvGenerator) Stop() {
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g.isGenerating = false
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}
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// GenHeader generates the flv header and sends it down the output chan for use
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// This will generally be called once at the start of file writing/transmission.
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func (g *flvGenerator) GenHeader() {
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header := flv.Header{
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AudioFlag: g.audioFlag,
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VideoFlag: g.videoFlag,
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}
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g.outputChan <- header.ToByteSlice()
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}
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// getNextTimestamp generates and returns the next timestamp based on current time
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func (g *flvGenerator) getNextTimestamp() (timestamp uint32) {
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if g.firstTag {
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g.startTime = time.Now()
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g.firstTag = false
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timestamp = 0
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return
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}
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timestamp = uint32(time.Now().Sub(g.startTime).Seconds() * float64(1000))
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return
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}
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// isKeyFrame returns true if the passed frame data represents that of a keyframe
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// TODO: clean this up and use conts for naltype codes
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func isKeyFrame(frame []byte) bool {
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byteChannel := make(chan byte, len(frame))
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for i := range frame {
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byteChannel <- frame[i]
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}
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for len(byteChannel) >= 5 {
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aByte := <-byteChannel
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for i := 1; aByte == 0x00 && i != 4; i++ {
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aByte = <-byteChannel
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if (aByte == 0x01 && i == 2) || (aByte == 0x01 && i == 3) {
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aByte = <-byteChannel
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nalType := aByte & 0x1F
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switch nalType {
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case interFrameCode:
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return false
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case keyFrameCode:
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return true
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case 6:
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return true
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}
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}
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}
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}
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return false
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}
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// isSequenceHeader returns true if the passed frame data represents that of a
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// a sequence header.
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// TODO: clean this up and use consts for the nalTypes
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func isSequenceHeader(frame []byte) bool {
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byteChannel := make(chan byte, len(frame))
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for i := range frame {
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byteChannel <- frame[i]
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}
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for len(byteChannel) >= 5 {
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aByte := <-byteChannel
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for i := 1; aByte == 0x00 && i != 4; i++ {
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aByte = <-byteChannel
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if (aByte == 0x01 && i == 2) || (aByte == 0x01 && i == 3) {
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aByte = <-byteChannel
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nalType := aByte & 0x1F
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switch nalType {
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case 1:
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return false
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case 5:
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return false
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case 6:
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return true
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case 7:
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return true
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case 8:
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return true
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}
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}
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}
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}
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return false
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}
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// generate takes in raw video data from the input chan and packetises it into
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// flv tags, which are then passed to the output channel.
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func (g *flvGenerator) generate() {
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g.GenHeader()
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var frameType byte
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var packetType byte
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for g.isGenerating {
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select {
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case videoFrame := <-g.inputChan:
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if isKeyFrame(videoFrame) {
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frameType = flv.KeyFrameType
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} else {
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frameType = flv.InterFrameType
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}
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if isSequenceHeader(videoFrame) {
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packetType = flv.SequenceHeader
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} else {
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packetType = flv.AVCNALU
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}
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timeStamp := g.getNextTimestamp()
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// Do we have video to send off ?
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if g.videoFlag {
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tag := flv.VideoTag{
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TagType: uint8(flv.VideoTagType),
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DataSize: uint32(len(videoFrame)) + flv.DataHeaderLength,
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Timestamp: timeStamp,
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TimestampExtended: flv.NoTimestampExtension,
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FrameType: frameType,
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Codec: flv.H264,
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PacketType: packetType,
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CompositionTime: 0,
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Data: videoFrame,
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PrevTagSize: uint32(videoHeaderSize + len(videoFrame)),
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}
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g.outputChan <- tag.ToByteSlice()
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}
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// Do we even have some audio to send off ?
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if g.audioFlag {
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// Not sure why but we need two audio tags for dummy silent audio
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// TODO: create constants or SoundSize and SoundType parameters
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tag := flv.AudioTag{
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TagType: uint8(flv.AudioTagType),
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DataSize: 7,
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Timestamp: timeStamp,
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TimestampExtended: flv.NoTimestampExtension,
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SoundFormat: flv.AACAudioFormat,
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SoundRate: 3,
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SoundSize: true,
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SoundType: true,
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Data: dummyAudioTag1Data,
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PrevTagSize: uint32(audioSize),
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}
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g.outputChan <- tag.ToByteSlice()
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tag = flv.AudioTag{
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TagType: uint8(flv.AudioTagType),
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DataSize: 21,
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Timestamp: timeStamp,
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TimestampExtended: flv.NoTimestampExtension,
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SoundFormat: flv.AACAudioFormat,
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SoundRate: 3,
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SoundSize: true,
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SoundType: true,
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Data: dummyAudioTag2Data,
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PrevTagSize: uint32(22),
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}
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g.outputChan <- tag.ToByteSlice()
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}
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}
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}
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}
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