Merge pull request #1072 from Alexander-Zyurkalov/Flesh-Out-Timecode-Message-Factories-736

feat: add MTC message generation functions and a Lua script example

Author: mfisher31

scripts/mtc_generator.lua

@@ -0,0 +1,80 @@
+--- MTC Generator.
+--
+-- Generates MIDI Timecode (MTC) based on the transport state.
+--
+-- @script      mtc_generator
+-- @type        DSP
+-- @license     GPL v3
+-- @author      Alexandr Zyurkalov
+
+local MidiBuffer = require ('el.MidiBuffer')
+local midi       = require ('el.midi')
+local bytes      = require ('el.bytes')
+
+-- Buffer to render filtered output
+local output = MidiBuffer.new ()
+
+-- Transport state and buffer properties
+local wasPlaying = false
+local lastSamplePosition = -1
+local sampleRate = 44100.0
+local bufSize    = 512
+local buffer     = bytes.new (10)
+local framesPerSecond = 24
+
+local function layout ()
+    return {
+        audio = { 0, 0 },
+        midi = { 0, 1 }
+    }
+end
+
+-- prepare for rendering
+local function prepare (rate, block)
+    -- reserve memory and clear the output buffer
+    output:reserve (256)
+    output:clear ()
+    sampleRate = rate
+    bufSize    = block
+end
+
+local function process (_, m, _, _, t)
+    -- Get MIDI input buffer from the MidiPipe
+    local input = m:get (1)
+
+    output:clear ()
+
+    local playing        = t:playing ()
+    local samplePosition = t:frame ()
+
+    local wasJumped = samplePosition ~= lastSamplePosition and lastSamplePosition >= 0
+    if not playing and (wasPlaying or wasJumped) then
+        local size = midi.mtcfullframetransport (buffer, samplePosition + bufSize - 1, sampleRate, framesPerSecond)
+        output:insertBytes (buffer, size, bufSize)
+    end
+
+    if playing then
+        local msg, frame, sentMessages = 0
+
+        repeat
+            sentMessages, msg, frame = midi.quarterframetransport (samplePosition, bufSize, sampleRate, framesPerSecond, sentMessages)
+            output:insertPacked (msg, frame)
+        until msg == nil
+    end
+
+    wasPlaying = playing
+    lastSamplePosition = samplePosition
+
+    -- DSP scripts use replace processing, so swap in the rendered output
+    input:swap (output)
+end
+
+return {
+    type = 'DSP',
+    layout = layout,
+    prepare = prepare,
+    process = process
+}
+
+-- SPDX-FileCopyrightText: Copyright (C) Kushview, LLC.
+-- SPDX-License-Identifier: GPL-3.0-or-later