feat: auto select iblksize based on simulation details

Project.toml

@@ -1,7 +1,7 @@
 name = "VirtualAcousticOcean"
 uuid = "629e117c-1786-4222-ab4a-1acab234d923"
 authors = ["Mandar Chitre <[email protected]>"]
-version = "0.3.0"
+version = "0.4.0"
 
 [deps]
 JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"

docs/uasp-protocol.md

@@ -147,3 +147,5 @@ DAC data is sent by the client to `uaspd`, and is appended to the DAC buffer pro
 
 Multiple channels are interleaved, i.e., data is organized as:<br>
 `[ch1_t1 ch2_t1 ch3_t1 ch4_t1 ch1_t2 ch2_t2 ch3_t2 ch4_t2 ...]`
+
+Note: Since data PDUs are sent as UDP packets, it is recommended that `nsamples` is chosen such that the packet size does not exceed the supported UDP MTU (typically 1432 bytes). Modern systems support UDP packets larger than this, but they are often fragmented at the physical layer and may have poor performance, and so not recommended.

src/sim.jl

@@ -38,7 +38,7 @@ Base.@kwdef struct Simulation{T}
   nodes::Vector{Node} = Node[]
   frequency::Float64                    # nominal frequency (Hz)
   irate::Float64 = 96000.0              # ADC samples/s
-  iblksize::Int = 256                   # ADC samples
+  iblksize::Int = 0                     # ADC samples
   orate::Float64 = 192000.0             # DAC samples/s
   txref::Float64 = 185.0                # dB re µPa @ 1m
   rxref::Float64 = -190.0               # dB re 1/µPa
@@ -58,7 +58,7 @@ with `UnderwaterAcoustics.jl`.
 
 Optional parameters:
 - `irate`: ADC frame rate for sampling aoustic signal (samples/s)
-- `iblksize`: ADC block size for streaming acoustic signal (samples)
+- `iblksize`: ADC block size for streaming acoustic signal (samples, 0 for auto)
 - `orate`: DAC frame rate for transmitting acoustic signal (samples/s)
 - `txref`: Conversion between DAC input and acoustic source level (dB re µPa @ 1m)
 - `rxref`: Conversion between acoustic receive level and ADC output (dB re 1/µPa)
@@ -104,25 +104,33 @@ end
 
 function _run(sim::Simulation, task::SimTask)
   sf = 10 ^ (sim.rxref / 20)
+  iblksize = _iblksize(sim)
   while task.t0 > 0
     Δt = task.t0 + (task.t / sim.irate) - time()
     Δt > 0 && sleep(Δt)
     for node ∈ sim.nodes
-      x = Matrix{Float32}(undef, sim.iblksize, length(node.tapes))
+      x = Matrix{Float32}(undef, iblksize, length(node.tapes))
       for i ∈ eachindex(node.tapes)
-        x[:,i] .= read(node.tapes[i], task.t, sim.iblksize)
-        x[:,i] .+= sf * real(record(noise(environment(sim.model)), sim.iblksize/sim.irate, sim.irate))
+        x[:,i] .= read(node.tapes[i], task.t, iblksize)
+        x[:,i] .+= sf * real(record(noise(environment(sim.model)), iblksize/sim.irate, sim.irate))
       end
       stream(sim, node, task.t, x)
     end
-    task.t += sim.iblksize
+    task.t += iblksize
     while !isempty(sim.timers) && sim.timers[1][1] ≤ task.t
       _, callback = popfirst!(sim.timers)
       @invokelatest callback(task.t)
     end
   end
 end
 
+# choose a block size that allows a data block to fit within an MTU of 1430 bytes or so
+function _iblksize(sim::Simulation)
+  sim.iblksize > 0 && return sim.iblksize
+  maxch = maximum(node -> length(node.tapes), sim.nodes)
+  min(353 ÷ maxch, 256)
+end
+
 """
     close(sim::Simulation)
 
@@ -261,7 +269,7 @@ Get parameter `k`. Returns `nothing` is parameter is unknown.
 function Base.get((sim, node)::Tuple{Simulation,Node}, k::Symbol)
   k === :time && return round(Int, sim.task.t / sim.irate)
   k === :iseqno && return node.seqno
-  k === :iblksize && return sim.iblksize
+  k === :iblksize && return _iblksize(sim)
   k === :irate && return sim.irate
   k === :irates && return [sim.irate]
   k === :ichannels && return length(node.relpos)