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首页 > 解决方案 > 我如何将 pitch_bend 更改添加到函数piano_roll_to_pretty_midi 以制作音乐？

python - 我如何将 pitch_bend 更改添加到函数piano_roll_to_pretty_midi 以制作音乐？

问题描述

我想使用函数piano_roll_to_pretty_midi 转换属性音乐，但我不知道如何将pitch_bend 更改添加到此函数，这是鳕鱼piano_roll：

def piano_roll_to_pretty_midi(piano_roll, fs=100, program=0):
    '''Convert a Piano Roll array into a PrettyMidi object
     with a single instrument.

    Parameters
    ----------
    piano_roll : np.ndarray, shape=(128,frames), dtype=int
        Piano roll of one instrument
    fs : int
        Sampling frequency of the columns, i.e. each column is spaced apart
        by ``1./fs`` seconds.
    program : int
        The program number of the instrument.

    Returns
    -------
    midi_object : pretty_midi.PrettyMIDI
        A pretty_midi.PrettyMIDI class instance describing
        the piano roll.

    '''
    notes, frames = piano_roll.shape
    pm = pretty_midi.PrettyMIDI()
    instrument = pretty_midi.Instrument(program=program)

    # pad 1 column of zeros so we can acknowledge inital and ending events
    piano_roll = np.pad(piano_roll, [(0, 0), (1, 1)], 'constant')

    # use changes in velocities to find note on / note off events
    velocity_changes = np.nonzero(np.diff(piano_roll).T)

    # keep track on velocities and note on times
    prev_velocities = np.zeros(notes, dtype=int)
    note_on_time = np.zeros(notes)

    for time, note in zip(*velocity_changes):
        # use time + 1 because of padding above
        velocity = piano_roll[note, time + 1]
        time = time / fs
        if velocity > 0:
            if prev_velocities[note] == 0:
                note_on_time[note] = time
                prev_velocities[note] = velocity
        else:
            pm_note = pretty_midi.Note(
                velocity=prev_velocities[note],
                pitch=note,
                start=note_on_time[note],
                end=time)
            instrument.notes.append(pm_note)
            prev_velocities[note] = 0
    pm.instruments.append(instrument)
    return pm

标签： python

解决方案

您将PitchBend对象添加到仪器的pitch_bends 列表中。这是一个 MWE，它从钢琴卷中添加音符并弯曲它们：

from pretty_midi import *
from numpy import *

roll = [[1, 0, 0, 0, 0, 0, 0],
        [0, 1, 0, 0, 0, 0, 0],
        [0, 0, 1, 0, 0, 0, 0],
        [0, 0, 0, 1, 0, 0, 0],
        [0, 0, 0, 0, 1, 0, 0],
        [0, 0, 0, 0, 0, 1, 0],
        [0, 0, 0, 0, 0, 0, 1]]
roll = array(roll).T

notes, frames = roll.shape
pm = PrettyMIDI()
instr = Instrument(program = 80)
roll = pad(roll, [(0, 0), (1, 1)], 'constant')
velocity_changes = nonzero(np.diff(roll).T)
prev_velocities = zeros(notes, dtype=int)
note_on_time = zeros(notes)
for time, note in zip(*velocity_changes):
    velocity = roll[note, time + 1]
    if velocity > 0:
        if prev_velocities[note] == 0:
            note_on_time[note] = time
            prev_velocities[note] = velocity
    else:
        start_time = note_on_time[note]
        pm_note = Note(
            velocity = 120,
            pitch = note + 40,
            start = start_time,
            end=time)
        instr.notes.append(pm_note)
        for i in range(20):
            time = start_time + i / 20
            bend = PitchBend(400 * i, time)
            instr.pitch_bends.append(bend)
        prev_velocities[note] = 0
pm.instruments.append(instr)
pm.write('test.mid')

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