我正在尝试将MIDI刻度/增量时间转换为毫秒,并且已经找到了一些有用的资源:
MIDI Delta时间刻度到秒
如何将midi时间轴转换为应该播放的实际时间轴
MIDI时间码规范
MTC
问题是我认为我没有正确使用这些信息.我试过应用Nik扩展的公式:
[ 1 min 60 sec 1 beat Z clocks ] | ------- * ------ * -------- * -------- | = seconds [ X beats 1 min Y clocks 1 ]
使用此测试MIDI文件中的元数据:
像这样:
self.toSeconds = 60.0 * self.t[0][2].clocks_per_click / (self.t[0][0].tempo * self.t[0][2].denominator) * 10
这最初看起来不错,但随后它似乎漂移了.这是一个使用Mido和pygame的基本可运行示例(假设pygame正确播放):
import threading
import pygame
from pygame.locals import *
from mido import MidiFile,MetaMessage
music_file = "Bee_Gees_-_Stayin_Alive-Voice.mid"
#audio setup
freq = 44100 # audio CD quality
bitsize = -16 # unsigned 16 bit
channels = 2 # 1 is mono, 2 is stereo
buffer = 1024 # number of samples
pygame.mixer.init(freq, bitsize, channels, buffer)
pygame.mixer.music.set_volume(0.8)
class MIDIPlayer(threading.Thread):
def __init__(self,music_file):
try:
#MIDI parsing
self.mid = MidiFile(music_file)
self.t = self.mid.tracks
for i, track in enumerate(self.mid.tracks):
print('Track {}: {}'.format(i, track.name))
for message in track:
if isinstance(message, MetaMessage):
if message.type == 'time_signature' or message.type == 'set_tempo' or message.type == 'key_signature':
print message
self.t0 = self.t[0][3:len(self.t[0])-1]
self.t0l = len(self.t0)
self.toSeconds = 60.0 * self.t[0][2].clocks_per_click / (self.t[0][0].tempo * self.t[0][2].denominator) * 10
print "self.toSeconds",self.toSeconds
#timing setup
self.event_id = 0
self.now = pygame.time.get_ticks()
self.play_music(music_file)
except KeyboardInterrupt:
pygame.mixer.music.fadeout(1000)
pygame.mixer.music.stop()
raise SystemExit
def play_music(self,music_file):
clock = pygame.time.Clock()
try:
pygame.mixer.music.load(music_file)
print "Music file %s loaded!" % music_file
except pygame.error:
print "File %s not found! (%s)" % (music_file, pygame.get_error())
return
pygame.mixer.music.play()
while pygame.mixer.music.get_busy():
# check if playback has finished
millis = pygame.time.get_ticks()
deltaMillis = self.t0[self.event_id].time * self.toSeconds * 1000
# print millis,deltaMillis
if millis - self.now >= deltaMillis:
print self.t0[self.event_id].text
self.event_id = (self.event_id + 1) % self.t0l
self.now = millis
clock.tick(30)
MIDIPlayer(music_file)
上面的代码应该做的是根据midi文件在正确的时间打印正确的歌词,但它会随着时间的推移而漂移.
将MIDI增量时间转换为秒/毫秒的正确方法是什么？
更新
基于CL的有用答案,我已更新代码以使用标题中的ticks_per_beat.由于存在单个set_tempo元消息,因此我始终使用此值:
import threading
import pygame
from pygame.locals import *
from mido import MidiFile,MetaMessage
music_file = "Bee_Gees_-_Stayin_Alive-Voice.mid"
#audio setup
freq = 44100 # audio CD quality
bitsize = -16 # unsigned 16 bit
channels = 2 # 1 is mono, 2 is stereo
buffer = 1024 # number of samples
pygame.mixer.init(freq, bitsize, channels, buffer)
pygame.mixer.music.set_volume(0.8)
class MIDIPlayer(threading.Thread):
def __init__(self,music_file):
try:
#MIDI parsing
self.mid = MidiFile(music_file)
self.t = self.mid.tracks
for i, track in enumerate(self.mid.tracks):
print('Track {}: {}'.format(i, track.name))
for message in track:
# print message
if isinstance(message, MetaMessage):
if message.type == 'time_signature' or message.type == 'set_tempo' or message.type == 'key_signature' or message.type == 'ticks_per_beat':
print message
self.t0 = self.t[0][3:len(self.t[0])-1]
self.t0l = len(self.t0)
self.toSeconds = 60.0 * self.t[0][2].clocks_per_click / (self.t[0][0].tempo * self.t[0][2].denominator) * 10
print "self.toSeconds",self.toSeconds
# append delta delays in milliseconds
self.delays = []
tempo = self.t[0][0].tempo
ticks_per_beat = self.mid.ticks_per_beat
last_event_ticks = 0
microseconds = 0
for event in self.t0:
delta_ticks = event.time - last_event_ticks
last_event_ticks = event.time
delta_microseconds = tempo * delta_ticks / ticks_per_beat
microseconds += delta_microseconds
print event.text,microseconds/1000000.0
self.delays.append(microseconds/1000)
#timing setup
self.event_id = 0
self.now = pygame.time.get_ticks()
self.play_music(music_file)
except KeyboardInterrupt:
pygame.mixer.music.fadeout(1000)
pygame.mixer.music.stop()
raise SystemExit
def play_music(self,music_file):
clock = pygame.time.Clock()
try:
pygame.mixer.music.load(music_file)
print "Music file %s loaded!" % music_file
except pygame.error:
print "File %s not found! (%s)" % (music_file, pygame.get_error())
return
pygame.mixer.music.play()
while pygame.mixer.music.get_busy():
# check if playback has finished
millis = pygame.time.get_ticks()
# deltaMillis = self.t0[self.event_id].time * self.toSeconds * 1000
deltaMillis = self.delays[self.event_id]
# print millis,deltaMillis
if millis - self.now >= deltaMillis:
print self.t0[self.event_id].text
self.event_id = (self.event_id + 1) % self.t0l
self.now = millis
clock.tick(30)
MIDIPlayer(music_file)
我根据转换为毫秒的时间打印的消息的时间看起来要好得多.然而,几秒钟后它仍然漂移.
我是否正确地将MIDI刻度转换为毫秒并跟踪更新循环中传递的毫秒数？
这是如何进行转换的:self.delays = []
tempo = self.t[0][0].tempo
ticks_per_beat = self.mid.ticks_per_beat
last_event_ticks = 0
microseconds = 0
for event in self.t0:
delta_ticks = event.time - last_event_ticks
last_event_ticks = event.time
delta_microseconds = tempo * delta_ticks / ticks_per_beat
microseconds += delta_microseconds
print event.text,microseconds/1000000.0
self.delays.append(microseconds/1000)
这就是在时间过去时检查是否遇到"提示"的方法:
millis = pygame.time.get_ticks()
deltaMillis = self.delays[self.event_id]
if millis - self.now >= deltaMillis:
print self.t0[self.event_id].text
self.event_id = (self.event_id + 1) % self.t0l
self.now = millis
clock.tick(30)
我不确定这个实现是否会错误地将MIDI增量刻度转换为毫秒,错误地检查基于毫秒的延迟是否通过或两者都有.
首先,您必须合并所有曲目,以确保正确处理速度变化事件.(如果首先将增量时间转换为绝对刻度值,这可能会更容易;否则,只要在另一个轨道的事件之间插入事件,就必须重新计算增量时间.)
然后,您必须为每个事件计算到最后一个事件的相对时间,如下面的伪代码.重要的是计算必须使用相对时间,因为速度可能随时发生变化:
tempo = 500000 # default: 120 BPM
ticks_per_beat = ... # from the file header
last_event_ticks = 0
microseconds = 0
for each event:
delta_ticks = event.ticks - last_event_ticks
last_event_ticks = event.ticks
delta_microseconds = tempo * delta_ticks / ticks_per_beat
microseconds += delta_microseconds
if event is a tempo event:
tempo = event.new_tempo
# ... handle event ...
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