RTMP study notes RTMP study notes 0

Ref: https://www.adobe.com/devnet/rtmp.html
Handshaking Sequence

---

uninitialized ----

C0 -->
C1 -->
<-- S0 必须在 C0或C1 之后
<-- S1 必须在 C0或C1 之后

---

version sent -----

C2 -->
C2 必须在 S1之后

---

Ack sent -----

<-- s2 必须在C1之后

---

Handshake Done ----

data -->
data必须在S2之后

  <-- data 必须在c2 之后

---

C0-> RTMP version 8 bits (=3)

 <- S0 RTMP version 8 bit (=3)

C1,S1 1536 bytes

time[4]:   stream 的参考基准时间
zero[4]:0
random bytes[1528]  乱数token

C2,S2 1536 bytes

time[4]:   C2: S1 的时间; S2: C1 的时间
time2[4]:  读取S1/C1的时间
random bytes[1528]: C1/S1的乱数token

Chunk:
| Basic Header | Message Header | Extended Timestamp | Chunk Data |
+--------------+----------------+--------------------+--------------+
Basic Header: 1~3 bytes, Chunk Stream ID + chunk type
Message Header:0,3,7, or 11 bytes,message的type
Extended Timestamp: 0 or 4 bytes
Chunk header = Basic Header + Message Header + Extended Timestamp
Chunk data: variable size.
Chunk Stream ID: 3~65599,

 0n = 64+n (64~319)
 1mn = 64+m + n*256 (64~65599)
 n (n !=0,1,2 one byte) (3~63)
 2 is reserved for level control

chunk type 高2位:format of Message header

Type 0: 11 byte 用于stream 开头
 timestamp[3]: 发送时间, 0xffffff  使用Extended Timestamp [32bits]
 message length[3]
 message type id[1]
 message stream id[4]
Type 1: 7 bytes
 timestamp delta[3]
 message length[3]
 message type id[1]
Type 2: 3 bytes ID 与长度跟前个chunk 同
 timestamp delta[3]
Type 3: no message header. timestamp , ID 与长度跟前个chunk 同

message type id

1,2,3,5,6 for protocol control message
8: audio
9: video

Protocol Control Messages
message stream ID 0: control stream
chunk stream ID 2: used in control stream
message type id

ID	Name	Fields	size	Meaning
1	Set Chunk Size	maximum chunk size	32 bits	Set maximum chunk size (1~0x7FFFFFFF)
2	Abort Message	chunk stream ID	32 bits	chunk stream ID message to be discard
3	Acknowledgement	sequnce number	32 bits	This field holds the number of bytes received so far.
5	Window Acknowledgement Size	window size	32 bits	inform the peer of the window size to use between sending acknowledgments
6	Set Peer Bandwidth	Acknowledgement Window size+Limit Type	32+8	sends this message to limit the output

• Limit type

0 - Hard: The peer SHOULD limit its output bandwidth to the indicated window size.
1 - Soft: The peer SHOULD limit its output bandwidth to the the window indicated in this message or the limit already in effect, whichever is smaller.
2 - Dynamic: If the previous Limit Type was Hard, treat this message as though it was marked Hard, otherwise ignore this message.