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Add endian information and describe time sync

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badaix 2021-01-04 13:29:12 +01:00
parent 8586e43d05
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doc/binary_protocol.md
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@ -4,6 +4,8 @@ Each message sent with the Snapcast binary protocol is split up into two parts:
- A base message that provides general information like time sent/received, type of the message, message size, etc - A base message that provides general information like time sent/received, type of the message, message size, etc
- A typed message that carries the rest of the information - A typed message that carries the rest of the information
The protocol is using little endian.
## Client joining process ## Client joining process
When a client joins a server, the following exchanges happen When a client joins a server, the following exchanges happen
@ -16,6 +18,10 @@ When a client joins a server, the following exchanges happen
1. Until the server sends this, the client shouldn't play any [Wire Chunk](#wire-chunk) messages 1. Until the server sends this, the client shouldn't play any [Wire Chunk](#wire-chunk) messages
1. The server will now send [Wire Chunk](#wire-chunk) messages, which can be fed to the audio decoder. 1. The server will now send [Wire Chunk](#wire-chunk) messages, which can be fed to the audio decoder.
1. When it comes time for the client to disconnect, the socket can just be closed. 1. When it comes time for the client to disconnect, the socket can just be closed.
1. Client periodically sends a [Time](#time) message, carrying a sent timestamp `t_client-sent`
1. Receives a Time response containing the client to server time delta `latency_c2s = t_server-recv - t_client-sent + t_network-latency` and the server sent timestamp `t_server-sent`
1. Calculates `latency_s2c = t_client-recv - t_server-sent + t_network_latency`
1. Calcutates the time diff between server and client as `(latency_c2s - latency_s2c) / 2`, eliminating the network latency (assumed to be symmetric)
## Messages ## Messages
@ -58,7 +64,7 @@ When a client joins a server, the following exchanges happen
| timestamp.sec | int32 | The second value of the timestamp when this part of the stream was recorded | | timestamp.sec | int32 | The second value of the timestamp when this part of the stream was recorded |
| timestamp.usec | int32 | The microsecond value of the timestamp when this part of the stream was recorded | | timestamp.usec | int32 | The microsecond value of the timestamp when this part of the stream was recorded |
| size | uint32 | Size of the following payload | | size | uint32 | Size of the following payload |
| payload | char[] | Buffer of data containing the codec header | | payload | char[] | Buffer of data containing the encoded PCM data (a decodable chunk per message) |
### Server Settings ### Server Settings