该项目为m7s的引擎部分，该部分逻辑是流媒体服务器的核心转发逻辑。仅包含最基础的功能，不含任何网络协议部分，但包含了一个插件的引入机制，其他功能均由插件实现
- 引擎初始化会加载配置文件，并逐个调用插件的Run函数
- 具有发布功能的插件，会通过GetStream函数创建一个流，即Stream对象，这个Stream对象随后可以被订阅
- Stream对象中含有两个列表，一个是VideoTracks一个是AudioTracks用来存放视频数据和音频数据
- 每一个VideoTrack或者AudioTrack中包含一个RingBuffer，用来存储发布者提供的数据，同时提供订阅者访问。
- 具有订阅功能的插件，会通过GetStream函数获取到一个流，然后选择VideoTracks、AudioTracks里面的RingBuffer进行连续的读取
以rtmp协议为例子
if pub := new(engine.Publisher); pub.Publish(streamPath) {
pub.Type = "RTMP"
stream = pub.Stream
err = nc.SendMessage(SEND_STREAM_BEGIN_MESSAGE, nil)
err = nc.SendMessage(SEND_PUBLISH_START_MESSAGE, newPublishResponseMessageData(nc.streamID, NetStream_Publish_Start, Level_Status))
} else {
err = nc.SendMessage(SEND_PUBLISH_RESPONSE_MESSAGE, newPublishResponseMessageData(nc.streamID, NetStream_Publish_BadName, Level_Error))
}默认会创建一个VideoTrack和一个AudioTrack 当我们接收到数据的时候就可以朝里面填充物数据了
rec_video = func(msg *Chunk) {
// 等待AVC序列帧
if msg.Body[1] != 0 {
return
}
vt := stream.VideoTracks[0]
var ts_video uint32
var info codec.AVCDecoderConfigurationRecord
//0:codec,1:IsAVCSequence,2~4:compositionTime
if _, err := info.Unmarshal(msg.Body[5:]); err == nil {
vt.SPSInfo, err = codec.ParseSPS(info.SequenceParameterSetNALUnit)
vt.SPS = info.SequenceParameterSetNALUnit
vt.PPS = info.PictureParameterSetNALUnit
}
vt.RtmpTag = msg.Body
nalulenSize := int(info.LengthSizeMinusOne&3 + 1)
rec_video = func(msg *Chunk) {
nalus := msg.Body[5:]
if msg.Timestamp == 0xffffff {
ts_video += msg.ExtendTimestamp
} else {
ts_video += msg.Timestamp // 绝对时间戳
}
for len(nalus) > nalulenSize {
nalulen := 0
for i := 0; i < nalulenSize; i++ {
nalulen += int(nalus[i]) << (8 * (nalulenSize - i - 1))
}
vt.Push(ts_video, nalus[nalulenSize:nalulen+nalulenSize])
nalus = nalus[nalulen+nalulenSize:]
}
}
close(vt.WaitFirst)
}在填充数据之前，需要获取到SPS和PPS，然后设置好，因为订阅者需要先发送这个数据 然后通过Track到Push函数将数据填充到RingBuffer里面去
subscriber := engine.Subscriber{
Type: "RTMP",
ID: fmt.Sprintf("%s|%d", conn.RemoteAddr().String(), nc.streamID),
}
if err = subscriber.Subscribe(streamPath); err == nil {
streams[nc.streamID] = &subscriber
err = nc.SendMessage(SEND_CHUNK_SIZE_MESSAGE, uint32(nc.writeChunkSize))
err = nc.SendMessage(SEND_STREAM_IS_RECORDED_MESSAGE, nil)
err = nc.SendMessage(SEND_STREAM_BEGIN_MESSAGE, nil)
err = nc.SendMessage(SEND_PLAY_RESPONSE_MESSAGE, newPlayResponseMessageData(nc.streamID, NetStream_Play_Reset, Level_Status))
err = nc.SendMessage(SEND_PLAY_RESPONSE_MESSAGE, newPlayResponseMessageData(nc.streamID, NetStream_Play_Start, Level_Status))
vt, at := subscriber.GetVideoTrack("h264"), subscriber.OriginAudioTrack
if vt != nil {
var lastVideoTime uint32
err = nc.SendMessage(SEND_FULL_VDIEO_MESSAGE, &AVPack{Payload: vt.RtmpTag})
subscriber.OnVideo = func(pack engine.VideoPack) {
if lastVideoTime == 0 {
lastVideoTime = pack.Timestamp
}
t := pack.Timestamp - lastVideoTime
lastVideoTime = pack.Timestamp
payload := codec.Nalu2RTMPTag(pack.Payload)
defer utils.RecycleSlice(payload)
err = nc.SendMessage(SEND_VIDEO_MESSAGE, &AVPack{Timestamp: t, Payload: payload})
}
}
if at != nil {
var lastAudioTime uint32
var aac byte
if at.SoundFormat == 10 {
aac = at.RtmpTag[0]
err = nc.SendMessage(SEND_FULL_AUDIO_MESSAGE, &AVPack{Payload: at.RtmpTag})
}
subscriber.OnAudio = func(pack engine.AudioPack) {
if lastAudioTime == 0 {
lastAudioTime = pack.Timestamp
}
t := pack.Timestamp - lastAudioTime
lastAudioTime = pack.Timestamp
payload := codec.Audio2RTMPTag(aac, pack.Payload)
defer utils.RecycleSlice(payload)
err = nc.SendMessage(SEND_AUDIO_MESSAGE, &AVPack{Timestamp: t, Payload: payload})
}
}
go subscriber.Play(at, vt)
}- 在发送数据前，需要先发送音视频的序列帧
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