在 Python MIDI MIDO read/save 文件中转换 time/tick

Question

以下程序使用MIDO读取'g1.mid'然后保存到'g1_new.mid'。我的问题是：在读取文件时，'msg.time'是一个float值，但在保存文件时，'time in Message'是一个整数，tick。在这种情况下，我们如何将 'msg.time' 转换为 'tick in message'？

from mido import MidiFile 
from mido import Message, MidiTrack

mid = MidiFile()
track = MidiTrack()
mid.tracks.append(track)

for msg in MidiFile('g1.mid'):
    if (not msg.is_meta):
        if (msg.type == 'note_on'):
            # how to convert msg.time to tick to fill in '?'
            track.append(Message('note_on', note=msg.note, velocity=msg.velocity, time=?))
        elif (msg.type == 'note_off'):
            # how to convert msg.time to tick to fill in '?'
            track.append(Message('note_off', note=msg.note, velocity=msg.velocity, time=?))
        elif (msg.type == 'program_change'):
            track.append(Message('program_change', program=msg.program, channel=msg.channel))

mid.save('g1_new.mid')

注意：这段代码在一个关于音乐生成的项目中。

Answer 1

当您遍历 MidiFile 对象本身时，时间戳会被显式转换：

class MidiFile(object):
    ...
    def __iter__(self):
        ...
        tempo = DEFAULT_TEMPO
        for msg in merge_tracks(self.tracks):
            # Convert message time from absolute time
            # in ticks to relative time in seconds.
            if msg.time > 0:
                delta = tick2second(msg.time, self.ticks_per_beat, tempo)
            else:
                delta = 0

            yield msg.copy(time=delta)

            if msg.type == 'set_tempo':
                tempo = msg.tempo

所以直接遍历 mid.tracks（或合并的轨道）。

在 Python MIDI MIDO read/save 文件中转换 time/tick

Convert time/tick in Python MIDI MIDO read/save file

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