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83 lines
2.8 KiB
Go
83 lines
2.8 KiB
Go
package rtmp
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import (
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"encoding/binary"
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"m7s.live/m7s/v5/pkg/util"
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)
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// RTMP协议中基本的数据单元称为消息(Message).
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// 当RTMP协议在互联网中传输数据的时候,消息会被拆分成更小的单元,称为消息块(Chunk).
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// 在网络上传输数据时,消息需要被拆分成较小的数据块,才适合在相应的网络环境上传输.
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// 理论上Type 0, 1, 2的Chunk都可以使用Extended Timestamp来传递时间
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// Type 3由于严禁携带Extened Timestamp字段.但实际上只有Type 0才需要带此字段.
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// 这是因为,对Type 1, 2来说,其时间为一个差值,一般肯定小于0x00FFFFF
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// 对于除Audio,Video以外的基它Message,其时间字段都可以是置为0的，似乎没有被用到.
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// 只有在发送视频和音频数据时,才需要特别的考虑TimeStamp字段.基本依据是,要以HandShake时为起始点0来计算时间.
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// 一般来说,建立一个相对时间,把一个视频帧的TimeStamp特意的在当前时间的基础上延迟3秒,则可以达到缓存的效果
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const (
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RTMP_CHUNK_HEAD_12 = 0 << 6 // Chunk Basic Header = (Chunk Type << 6) | Chunk Stream ID.
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RTMP_CHUNK_HEAD_8 = 1 << 6
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RTMP_CHUNK_HEAD_4 = 2 << 6
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RTMP_CHUNK_HEAD_1 = 3 << 6
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)
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type Chunk struct {
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ChunkHeader
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AVData RTMPData
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MsgData RtmpMessage
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}
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type ChunkHeader struct {
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ChunkStreamID uint32 `json:""`
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Timestamp uint32 `json:""` // 3 byte
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MessageLength uint32 `json:""` // 3 byte
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MessageTypeID byte `json:""` // 1 byte
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MessageStreamID uint32 `json:""` // 4 byte
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// Extended Timestamp (0 or 4 bytes): This field is present in certain
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// circumstances depending on the encoded timestamp or timestamp
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// delta field in the Chunk Message header. See Section 5.3.1.3 for
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// more information
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ExtendTimestamp uint32 `json:",omitempty"` // 标识该字段的数据可忽略
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}
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func (c *ChunkHeader) SetTimestamp(timestamp uint32) {
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if timestamp >= 0xFFFFFF {
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c.ExtendTimestamp = timestamp
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c.Timestamp = 0xFFFFFF
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} else {
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c.ExtendTimestamp = 0
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c.Timestamp = timestamp
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}
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}
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// ChunkBasicHeader会决定ChunkMessgaeHeader,ChunkMessgaeHeader有4种(0,3,7,11 Bytes),因此可能有4种头.
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// 1 -> ChunkBasicHeader(1) + ChunkMessageHeader(0)
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// 4 -> ChunkBasicHeader(1) + ChunkMessageHeader(3)
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// 8 -> ChunkBasicHeader(1) + ChunkMessageHeader(7)
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// 12 -> ChunkBasicHeader(1) + ChunkMessageHeader(11)
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func (h *ChunkHeader) WriteTo(t byte, b *util.Buffer) {
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b.Reset()
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csid := byte(h.ChunkStreamID)
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b.WriteByte(t + csid)
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if t < RTMP_CHUNK_HEAD_1 {
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b.WriteUint24(h.Timestamp)
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if t < RTMP_CHUNK_HEAD_4 {
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b.WriteUint24(h.MessageLength)
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b.WriteByte(h.MessageTypeID)
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if t < RTMP_CHUNK_HEAD_8 {
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binary.LittleEndian.PutUint32(b.Malloc(4), h.MessageStreamID)
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}
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}
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}
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if h.Timestamp == 0xffffff {
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b.WriteUint32(h.ExtendTimestamp)
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}
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}
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