# DrumScript/notation_generator/midi_exporter.py
"""
This module takes classified drum events and renders them into a standard MIDI file.
Uses event['time'] and event['drums'].
"""
import os
import pretty_midi
from drumscript.notation_generator.constants import DRUM_NOTATION_MAP
[docs]
def export_to_midi(classified_events: list[dict], output_path: str, tempo: float = 120.0):
"""
Takes a list of event dictionaries and writes a standard .mid file.
:param classified_events: List of dicts containing 'time_sec' and 'instruments'.
:param output_path: Where to save the file (e.g., 'output/drum_score.mid').
:param tempo: The detected BPM of the track.
"""
# 1. Initialise a new MIDI object with the detected tempo
midi = pretty_midi.PrettyMIDI(initial_tempo=tempo)
# 2. Create a Drum Track (program=0, is_drum=True forces it to MIDI Channel 10)
drum_track = pretty_midi.Instrument(program=0, is_drum=True, name="DrumScript Output")
# 3. Loop through your beautifully classified timeline
for event in classified_events:
# time_sec = event["time"]
time_sec = event["time_sec"]
# instruments = event["drums"]
instruments = event["instruments"]
# Multiple instruments can hit at the exact same millisecond!
for inst in instruments:
# Check if our physics engine spit out an instrument we have in our map
if inst in DRUM_NOTATION_MAP:
midi_pitch = DRUM_NOTATION_MAP[inst]["midi_program"]
# Create the MIDI Note.
# (Drums don't hold sustain, so a 0.1s duration is standard for sheet music)
note = pretty_midi.Note(
velocity=100, # Default strong hit
pitch=midi_pitch, # E.g., 36 for Kick, 38 for Snare
start=time_sec, # The exact millisecond from onset_detector
end=time_sec + 0.1,
)
drum_track.notes.append(note)
else:
# If the classifier guessed 'unknown', we skip it for the clean score
pass
# 4. Add the finished track to the file and save it
midi.instruments.append(drum_track)
# Ensure directory exists
os.makedirs(os.path.dirname(output_path), exist_ok=True)
midi.write(output_path)
print(f"SUCCESS: MIDI file generated at -> {output_path}")
# --------------------------------------------------------------------------uncomment during testing
# from datetime import datetime
# print("\n# ------------------------------------------------------------------------------------")
# datetimestamp = datetime.now()
# print(f'\ndate/time: {datetimestamp}')
# --------------------------------------------------------------------------------------------------
DrumScript