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Add endian information and describe time sync

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badaix 2021-01-04 13:29:12 +01:00
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commit 92d39212ae
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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 typed message that carries the rest of the information
The protocol is using little endian.
## Client joining process
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. 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. 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
@ -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.usec | int32 | The microsecond value of the timestamp when this part of the stream was recorded |
| 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