Add example application midi_file_player.py

Author: mgeier

doc/examples.rst

@@ -45,6 +45,13 @@ MIDI Chord Generator
 
 .. literalinclude:: ../examples/midi_chords.py
 
+MIDI File Player
+----------------
+
+:download:`midi_file_player.py <../examples/midi_file_player.py>`
+
+.. literalinclude:: ../examples/midi_file_player.py
+
 Simple MIDI Synth
 -----------------
 

examples/midi_file_player.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""Play a MIDI file.
+
+This uses the "mido" module for handling MIDI: https://mido.readthedocs.io/
+
+Pass the MIDI file name as first command line argument.
+
+If a MIDI port name is passed as second argument, a connection is made.
+
+"""
+import sys
+import threading
+
+import jack
+from mido import MidiFile
+
+argv = iter(sys.argv)
+next(argv)
+filename = next(argv, '')
+connect_to = next(argv, '')
+if not filename:
+    sys.exit('Please specify a MIDI file')
+try:
+    mid = iter(MidiFile(filename))
+except Exception as e:
+    sys.exit(type(e).__name__ + ' while loading MIDI: ' + str(e))
+
+client = jack.Client('MIDI-File-Player')
+port = client.midi_outports.register('output')
+event = threading.Event()
+msg = next(mid)
+fs = None  # sampling rate
+offset = 0
+
+
+@client.set_process_callback
+def process(frames):
+    global offset
+    global msg
+    port.clear_buffer()
+    while True:
+        if offset >= frames:
+            offset -= frames
+            return  # We'll take care of this in the next block ...
+        # Note: This may raise an exception:
+        port.write_midi_event(offset, msg.bytes())
+        try:
+            msg = next(mid)
+        except StopIteration:
+            event.set()
+            raise jack.CallbackExit
+        offset += round(msg.time * fs)
+
+
+@client.set_samplerate_callback
+def samplerate(samplerate):
+    global fs
+    fs = samplerate
+
+
+@client.set_shutdown_callback
+def shutdown(status, reason):
+    print('JACK shutdown:', reason, status)
+    event.set()
+
+
+with client:
+    if connect_to:
+        port.connect(connect_to)
+    print('Playing', repr(filename), '... press Ctrl+C to stop')
+    try:
+        event.wait()
+    except KeyboardInterrupt:
+        print('\nInterrupted by user')