查看RTMP study notes的源代码 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

<u>Protocol Control Messages</u>
message stream ID 0: control stream
chunk stream ID 2: used in control stream
message type id
{| class="wikitable" style="width:100%"
! 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.