Editing SimTX API/Packets/MonitorBlock

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{{SimTX packet
| name = MonitorBlock
| frame = ServerFrame
| field = 31
| member = monitor_block
| direction = s2c
| session = [[SimTX API/Control session|Control]], [[SimTX API/Moderation session|moderation]]
| roles = <code>ROLE_CONTROL</code>, <code>ROLE_MODERATION</code>.
| permission = None
| group = control
| file = control.proto
}}
'''MonitorBlock''' carries a block of a monitored transmitter's signal, as requested with [[SimTX API/Packets/StartMonitor|StartMonitor]]. Blocks arrive in real time until [[SimTX API/Packets/MonitorEnd|MonitorEnd]] or [[SimTX API/Packets/StopMonitor|StopMonitor]].

== Definition ==
<syntaxhighlight lang="protobuf">
message MonitorBlock {
  bytes session_id = 1;
  int32 sample_rate = 2;
  repeated float iq = 3;       // interleaved I, Q
}
</syntaxhighlight>

== Fields ==
{| class="wikitable"
! # !! Field !! Type !! Description
|-
| 1 || <code>session_id</code> || <code>bytes</code> || The monitored transmitter.
|-
| 2 || <code>sample_rate</code> || <code>int32</code> || Complex samples per second: the transmitter's processing rate.
|-
| 3 || <code>iq</code> || <code>repeated float</code> || Complex baseband, I and Q interleaved, centred on the carrier. At most 262,144 floats.
|}

== Usage ==
* Demodulate the IQ with the transmitter's modulation to hear the signal.
* <code>sample_rate</code> is the transmitter's processing rate: its declared sample rate, at least 240,000 for <code>WFM</code>, at most 10,000,000.
* Monitor blocks share the session's output queue, which holds at most 64 frames or 8 MiB. A client that cannot keep up has its connection closed. Read on a dedicated thread.
* A wideband transmitter produces a lot of data: 10 MS/s of complex floats is 80 MB/s.

== See also ==
* [[SimTX API/Packets/StartMonitor|StartMonitor]]

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