MicroPython Forum (Archive)

Hello,
I coded a module to parse MIDI files, that is, to read a MIDI file and return all the events in the file, calculating time between events.

Available at https://github.com/bixb922/umidiparser under MIT license.

Example:

import umidiparser
import utime
for event in umidiplay.MidiFile("example.mid"):
# Wait until this event is due
utime.sleep_us( event.delta_us )
# Process the event according to type
if event.status == umidiplay.NOTE_ON:
... start the note event.note on event.channel with event.velocity
elif event.status == umidiplay.NOTE_OFF :
... stop the note event.note stop to sound ...
elif event.status == umidiplay.PROGRAM_CHANGE:
... change midi program to event.program on event.channel ....
else:
# Show all events not processed
print("other event", event )

This module does not contain a sound synthesizer, only the capabilities to read and interpret a MIDI file.

Memory and CPU usage is optimized for a microcontroller with limited resources with Micropython. CPU and memory usage can be lowered even more by reusing the same MidiEvent over and over during the process:

for event in MidiFile("example.mid", reuse_event_object=True ):
... process event....

Normally the complete midi file will be buffered in RAM when opening the file. If RAM is scarce or may be fragmented, use:

for event in MidiFile("example.mid", buffer_size=100 ):
.... process event...
This will allocate buffer_size bytes as a buffer for each track in the midi file, open one file descriptor for each track and then read the file piecemeal. CPU usage may increase about 10% slightly (about 10%) but RAM usage is limited to the buffer_size bytes per track, and you can process a files much larger than the available heap or RAM. See "CPU AND MEMORY" below.

This module will calculate the time between events, using the parameters and events available in the MIDI file (pulses per beat field in the file header and set tempo events).

I hope this can be useful.

Looking forward to a simple video demo.

Ooh, neat. I am a complete MIDI numpty, but I can follow how this works. What annoyance can I bring using this plus a simple piezo buzzer, I wonder?

If anyone's looking to convert MIDI notes (0 - 127) to frequencies, will do it (as suggested by Note names, MIDI numbers and frequencies).

I got it to make noise! Glorious dreadful noise!
MicroPython MIDI mayhem (kinda)

Hello @scruss,
I liked that!! Almost obnoxious!!
Cheers!!

Hi!

A few months ago, I modified an existing project based on a BluePill to play MIDI files from an Amstrad CPC. All written in C, of course, in order to manage the timings with the CPC bus.

Today, I'm digging in the RPi Pico, and I'm porting my code to micropython / PIO, so the umidiparser library will be very helpful.

Thanks for sharing!