Add test synth to debug capture alignment

diff --git a/scripts/_spike_synth.lua b/scripts/_spike_synth.lua
new file mode 100644 (file)
index 0000000..167e0e2
--- /dev/null
+++ b/scripts/_spike_synth.lua
@@ -0,0 +1,37 @@
+ardour {
+       ["type"]    = "dsp",
+       name        = "Spike Synth",
+       category    = "Instrument",
+       license     = "MIT",
+       author      = "Ardour Lua Task Force",
+       description = [[A debug and test-instrumentation synth. This plugin is useful with Ardour's "Dummy" backend "Engine-Pulse" mode to verify capture alignment. This plugin generate the exact same audio-signal from MIDI data that the backend also generates: Note-on: +1, Note-off: -1.]]
+}
+
+function dsp_ioconfig ()
+       return { { midi_in = 1, audio_in = 0, audio_out =  1} }
+end
+
+function dsp_run (ins, outs, n_samples)
+       local a = {}
+       for s = 1, n_samples do a[s] = 0 end
+
+       for c = 1,#outs do
+               ARDOUR.DSP.memset (outs[c], 0, n_samples)
+       end
+
+       assert (type(midiin) == "table")
+       for _,b in pairs (midiin) do
+               local t = b["time"] -- t = [ 1 .. n_samples ]
+               local d = b["data"] -- get midi-event
+               if (#d == 3 and (d[1] & 240) == 144) then -- note on
+                       for c = 1,#outs do
+                               outs[c]:array()[t] = 1.0
+                       end
+               end
+               if (#d == 3 and (d[1] & 240) == 128) then -- note off
+                       for c = 1,#outs do
+                               outs[c]:array()[t] = -1.0
+                       end
+               end
+       end
+end