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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# recrpn.py
#
"""Receive and decode RPN messages.
RPN (registered parameter number) messages are just regular Control Change
messages with a special semantic. To change an RPN value, the sender first
sends the parameter number with CC #100 (LSB) and #101 (MSB) and then the
parameter value with CC #38 (LSB) and #6 (MSB). Both the parameter number and
value are 14-bit values (MSB * 128 + LSB).
See also: http://www.somascape.org/midi/tech/spec.html#rpns
"""
import time
from collections import defaultdict
from rtmidi.midiconstants import (CONTROL_CHANGE, DATA_DECREMENT,
DATA_ENTRY_LSB, DATA_ENTRY_MSB,
DATA_INCREMENT, RPN_LSB, RPN_MSB)
from rtmidi.midiutil import open_midiinput
class RPNDecoder:
def __init__(self, channel=1):
self.channel = (channel - 1) & 0xF
self.rpn = 0
self.values = defaultdict(int)
self.last_changed = None
def __call__(self, event, data=None):
msg, deltatime = event
# event type = upper four bits of first byte
if msg[0] == (CONTROL_CHANGE | self.channel):
cc, value = msg[1], msg[2]
if cc == RPN_LSB:
self.rpn = (self.rpn >> 7) * 128 + value
elif cc == RPN_MSB:
self.rpn = value * 128 + (self.rpn & 0x7F)
elif cc == DATA_INCREMENT:
self.set_rpn(self.rpn, min(2 ** 14, self.values[self.rpn] + 1))
elif cc == DATA_DECREMENT:
self.set_rpn(self.rpn, max(0, self.values[self.rpn] - 1))
elif cc == DATA_ENTRY_LSB:
self.set_rpn(self.rpn,
(self.values[self.rpn] >> 7) * 128 + value)
elif cc == DATA_ENTRY_MSB:
self.set_rpn(self.rpn,
value * 128 + (self.values[self.rpn] & 0x7F))
def set_rpn(self, rpn, value):
self.values[rpn] = value
self.last_changed = rpn
def main(args=None):
decoder = RPNDecoder()
m_in, port_name = open_midiinput(args[0] if args else None)
m_in.set_callback(decoder)
try:
while True:
rpn = decoder.last_changed
if rpn:
print("RPN %i: %i" % (rpn, decoder.values[rpn]))
decoder.last_changed = None
time.sleep(0.1)
except KeyboardInterrupt:
pass
finally:
m_in.close_port()
del m_in
if __name__ == '__main__':
import sys
sys.exit(main(sys.argv[1:]) or 0)
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