Editing SimTX API v24/Packets/IqBlock

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{{SimTX packet v24
| name = IqBlock
| id = 2
| hex = 0x02
| direction = s2c
| session = [[SimTX API v24/Receiver session|Receiver]]
| size = 8 + chunkSamples × 4 bytes (INT16)
| permission = None
| group = receiver
}}
'''IqBlock''' carries one block of received complex baseband samples. A receiver session with role 1 receives a continuous stream of them after the [[SimTX API v24/Packets/IqStreamDescriptor|IqStreamDescriptor]], at the rate of the simulation. Role 6 receives [[SimTX API v24/Packets/TimedIqBlock|TimedIqBlock]] instead.

== Layout ==
{| class="wikitable"
! Field !! Type !! Description
|-
| <code>packetId</code> || <code>u8</code> || Always <code>2</code>.
|-
| <code>payloadLength</code> || <code>i32</code> || Length of the payload in bytes. At most 1 MiB.
|-
| <code>blockScale</code> || <code>f32</code> || First 4 bytes of the payload. Scale factor for this block.
|-
| <code>samples</code> || <code>chunkSamples × (I, Q)</code> || Remainder of the payload. Interleaved I and Q integers: <code>i16</code> each for INT16, <code>i8</code> each for INT8.
|}

== Decoding ==
<syntaxhighlight lang="text">
I = i_raw × blockScale / 32767        (INT16; use 127 for INT8)
Q = q_raw × blockScale / 32767
</syntaxhighlight>

* A client should check that <code>payloadLength</code> equals <code>4 + chunkSamples × 2 × bytesPerComponent</code> and treat anything else as a protocol error.
* <code>blockScale</code> is the block's peak component magnitude, at least 10<sup>−9</sup>. The server quantises each component as <code>round(x × 32767 / blockScale)</code>.
* A magnitude of 1.0 corresponds to −12 dBm at the receiver input. Components are clipped at ±1.0 before quantisation, so strong signals overload the receiver.

== Delivery ==
* Blocks are sent in real time. The server queues at most 8 blocks per connection and drops the oldest when the queue is full. Missing blocks are not marked; a client that needs to detect gaps should use role 6 and its timestamps.
* A client that does not read for 5 seconds is disconnected.

== See also ==
* [[SimTX API v24/Receiver session#Decoding samples|Decoding samples]]

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