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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"midi_file_player.py + multiprocessing","articleBody":"Hi,\r\nI'm trying to modify [this](https://github.com/spatialaudio/jackclient-python/blob/master/examples/midi_file_player.py) example in order to make it compatible with [multiprocessing](https://docs.python.org/3/library/multiprocessing.html).\r\n\r\nMainly I had to rename some global variables:\r\n\r\n```\r\n#!/usr/bin/env python3\r\n\r\nimport sys\r\nimport threading\r\n\r\nimport jack\r\nfrom mido import MidiFile\r\nfrom multiprocessing import Process\r\n\r\nmidi_file = '../Musica/Mozart/k265/Zwölf-Variationen.midi'\r\n\r\ntry:\r\n    mid = iter(MidiFile(midi_file))\r\nexcept Exception as e:\r\n    sys.exit(type(e).__name__ + ' while loading MIDI: ' + str(e))\r\n\r\nclient = jack.Client('Luces')\r\nmidi_port = client.midi_outports.register('output')\r\nmidi_event = threading.Event()\r\nmidi_msg = next(mid)\r\nmidi_fs = None  # sampling rate\r\nmidi_offset = 0\r\n\r\n@client.set_process_callback\r\ndef process(frames):\r\n    global midi_offset\r\n    global midi_msg\r\n    midi_port.clear_buffer()\r\n    while True:\r\n        if midi_offset \u003e= frames:\r\n            midi_offset -= frames\r\n            return  # We'll take care of this in the next block ...\r\n        # Note: This may raise an exception:\r\n        midi_port.write_midi_event(midi_offset, midi_msg.bytes())\r\n        try:\r\n            midi_msg = next(mid)\r\n        except StopIteration:\r\n            midi_event.set()\r\n            raise jack.CallbackExit\r\n        midi_offset += round(midi_msg.time * midi_fs)\r\n\r\n@client.set_samplerate_callback\r\ndef samplerate(samplerate):\r\n    global midi_fs\r\n    midi_fs = samplerate\r\n\r\n@client.set_shutdown_callback\r\ndef shutdown(status, reason):\r\n    print('JACK shutdown:', reason, status)\r\n    midi_event.set()\r\n\r\ndef run_midi():\r\n    with client:\r\n        print('Playing', repr(midi_file), '... press Ctrl+C to stop')\r\n        try:\r\n            midi_event.wait()\r\n        except KeyboardInterrupt:\r\n            print('\\nInterrupted by user')\r\n\r\nif __name__ == \"__main__\":\r\n    processes = [Process(target=run_midi)]\r\n    for p in processes:\r\n        p.start()\r\n    for p in processes:\r\n        p.join()\r\n```\r\n\r\nNow I get this error at the end of the execution:\r\n\r\n```\r\nPlaying '../Musica/Mozart/k265/Zwölf-Variationen.midi' ... press Ctrl+C to stop\r\nCannot read socket fd = 5 err = Success\r\nCheckRes error\r\nJackSocketClientChannel read fail\r\nJACK shutdown: JACK server has been closed \u003cjack.Status 0x21: failure, server_error\u003e\r\n```\r\n\r\nHow can I fix it?\r\n\r\nThank you!\r\n\r\nCarlo","author":{"url":"https://github.com/Stemby","@type":"Person","name":"Stemby"},"datePublished":"2020-11-07T05:01:06.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/99/jackclient-python/issues/99"}