在过去的几周中，我一直在从事一个对我来说很新的项目，并且我正在学习。我正在使用Raspberry Pi 2构建一个合成器，并使用Python3对其进行编码，因为我对该语言有一些基本知识，但没有太多实际经验。到目前为止，我的表现还不错，但是现在我碰到了我知道最终会碰到的墙:性能。
我一直在使用Pygame及其声音模块来创建所需的声音，然后使用自己的数学算法为每种声音计算ADS(H)R音量包络。我用8个电位器调整了这个信封。其中3个控制着“攻击”，“衰减”，“释放”的时间长度(以秒为单位)，另一个控制着持续时间。然后，我又添加了四个控制信封各个部分曲率的花盆(除了其中一个，它设置了Sustain的Hold值)。我还连接了一个PiTFT屏幕，它可以绘制整个信封的当前形状和长度，并打印出ADSR的当前值。
要播放声音，我使用4x4 Adafruit网格板，并且通过不同的按钮组合，我可以播放C0和C8之间的每个音符。
我使用SciPy和NumPy来创建不同种类的声波，例如正弦波，方波，三角波，锯齿波，脉冲波和噪声波。
由于我一直在使用常规的for循环来根据ADSR包络来改变声音的音量，因此运行PlaySound功能需要一段时间才能完成(当然取决于我的ADSR设置)。这促使我尝试使用线程。我不知道我是否以最佳方式使用它，是否应该完全使用它，但这是我想到复音的唯一方法。否则，它必须等到声音完成后才能恢复主循环。现在，我可以同时演奏多个音符。好吧，至少有两个音符。之后，它滞后了，直到之前的声音之一完成后，第三个声音才开始播放。
我已经进行了一些测试和检查，我应该能够同时运行多达4个线程，但是我可能会丢失一些东西。一种猜测是系统本身保留了两个线程(核心)供其他用途。
我也意识到Python并不是使用的最有效的语言，我也一直在研究Pure Data，但是我很难理解它(我更喜欢代码而不是click-drag-gui )。我想尽可能长时间地使用Python。我可能会考虑使用pyo，但是我认为我必须首先从头开始编写我的代码(我愿意这样做，但我现在还不想放弃我的代码)。
所以。这是我的问题:如何将其优化为真正的复音？仅靠两个音符是不够的。我应该完全跳过线程吗？我可以用更好，更省钱的方式实现ADSR信封吗？如何清理凌乱的数学？我忽略了其他哪些性能瓶颈？目前在屏幕上绘制的Pygame似乎可以忽略不计，因为如果我完全禁用它，则几乎没有任何区别。到目前为止，这是我的代码:
import pygame
from pygame.mixer import Sound, get_init, pre_init, get_num_channels
from array import array
import RPi.GPIO as GPIO
import alsaaudio
import time
import Adafruit_Trellis
import Adafruit_MCP3008
import math
import _thread
import os
import multiprocessing
import numpy as np
from scipy import signal as sg
import struct
#print(str(multiprocessing.cpu_count()))
os.putenv('SDL_FBDEV','/dev/fb1')
fps = pygame.time.Clock()
FRAMERATE = 100
MINSEC = 1/FRAMERATE
BLUE = ( 0, 0, 255)
WHITE = (255, 255, 255)
DARKRED = (128, 0, 0)
DARKBLUE = ( 0, 0, 128)
RED = (255, 0, 0)
GREEN = ( 0, 255, 0)
DARKGREEN = ( 0, 128, 0)
YELLOW = (255, 255, 0)
DARKYELLOW = (128, 128, 0)
BLACK = ( 0, 0, 0)
PTCH = [ 1.00, 1.059633027522936, 1.122324159021407, 1.18960244648318,
1.259938837920489, 1.335168195718654, 1.414067278287462,
1.498470948012232, 1.587767584097859, 1.681957186544343,
1.782262996941896, 1.888073394495413, 2.00 ]
FREQ = { # Parsed from http://www.phy.mtu.edu/~suits/notefreqs.html
'C0': 16.35, 'Cs0': 17.32, 'D0': 18.35, 'Ds0': 19.45, 'E0': 20.60,
'F0': 21.83, 'Fs0': 23.12, 'G0': 24.50, 'Gs0': 25.96, 'A0': 27.50,
'As0': 29.14, 'B0': 30.87, 'C1': 32.70, 'Cs1': 34.65, 'D1': 36.71,
'Ds1': 38.89, 'E1': 41.20, 'F1': 43.65, 'Fs1': 46.25, 'G1': 49.00,
'Gs1': 51.91, 'A1': 55.00, 'As1': 58.27, 'B1': 61.74, 'C2': 65.41,
'Cs2': 69.30, 'D2': 73.42, 'Ds2': 77.78, 'E2': 82.41, 'F2': 87.31,
'Fs2': 92.50, 'G2': 98.00, 'Gs2': 103.83, 'A2': 110.00, 'As2': 116.54,
'B2': 123.47, 'C3': 130.81, 'Cs3': 138.59, 'D3': 146.83, 'Ds3': 155.56,
'E3': 164.81, 'F3': 174.61, 'Fs3': 185.00, 'G3': 196.00, 'Gs3': 207.65,
'A3': 220.00, 'As3': 233.08, 'B3': 246.94, 'C4': 261.63, 'Cs4': 277.18,
'D4': 293.66, 'Ds4': 311.13, 'E4': 329.63, 'F4': 349.23, 'Fs4': 369.99,
'G4': 392.00, 'Gs4': 415.30, 'A4': 440.00, 'As4': 466.16, 'B4': 493.88,
'C5': 523.25, 'Cs5': 554.37, 'D5': 587.33, 'Ds5': 622.25, 'E5': 659.26,
'F5': 698.46, 'Fs5': 739.99, 'G5': 783.99, 'Gs5': 830.61, 'A5': 880.00,
'As5': 932.33, 'B5': 987.77, 'C6': 1046.50, 'Cs6': 1108.73, 'D6': 1174.66,
'Ds6': 1244.51, 'E6': 1318.51, 'F6': 1396.91, 'Fs6': 1479.98, 'G6': 1567.98,
'Gs6': 1661.22, 'A6': 1760.00, 'As6': 1864.66, 'B6': 1975.53, 'C7': 2093.00,
'Cs7': 2217.46, 'D7': 2349.32, 'Ds7': 2489.02, 'E7': 2637.02, 'F7': 2793.83,
'Fs7': 2959.96, 'G7': 3135.96, 'Gs7': 3322.44, 'A7': 3520.00,
'As7': 3729.31, 'B7': 3951.07,
'C8': 4186.01, 'Cs8': 4434.92, 'D8': 4698.64, 'Ds8': 4978.03,
}
buttons = ['A',PTCH[9],PTCH[10],PTCH[11],'B',PTCH[6],PTCH[7],PTCH[8],'C',PTCH[3],PTCH[4],PTCH[5],PTCH[12],PTCH[0],PTCH[1],PTCH[2] ]
octaves = { 'BASE':'0', 'A':'1', 'B':'2', 'C':'3', 'AB':'4', 'AC':'5', 'BC':'6', 'ABC':'7' }
class Note(pygame.mixer.Sound):
def __init__(self, frequency, volume=.1):
self.frequency = frequency
self.oktostop = False
Sound.__init__(self, self.build_samples())
self.set_volume(volume)
def playSound(self, Aval, Dval, Sval, Rval, Acurve, Dcurve, Shold, Rcurve, fps):
self.set_volume(0)
self.play(-1)
if Aval >= MINSEC:
Alength = round(Aval*FRAMERATE)
for num in range(0,Alength+1):
fps.tick_busy_loop(FRAMERATE)
volume = (Acurve[1]*pow(num*MINSEC,Acurve[0]))/100
self.set_volume(volume)
#print(fps.get_time()," ",str(volume))
else:
self.set_volume(100)
if Sval <= 1 and Sval > 0 and Dval >= MINSEC:
Dlength = round(Dval*FRAMERATE)
for num in range(0,Dlength+1):
fps.tick_busy_loop(FRAMERATE)
volume = (Dcurve[1]*pow(num*MINSEC,Dcurve[0])+100)/100
self.set_volume(volume)
#print(fps.get_time()," ",str(volume))
elif Sval <= 1 and Sval > 0 and Dval < MINSEC:
self.set_volume(Sval)
else:
self.set_volume(0)
if Shold >= MINSEC:
Slength = round(Shold*FRAMERATE)
for num in range(0,Slength+1):
fps.tick_busy_loop(FRAMERATE)
while True:
if self.oktostop:
if Sval > 0 and Rval >= MINSEC:
Rlength = round(Rval*FRAMERATE)
for num in range(0,Rlength+1):
fps.tick_busy_loop(FRAMERATE)
volume = (Rcurve[1]*pow(num*MINSEC,Rcurve[0])+(Sval*100))/100
self.set_volume(volume)
#print(fps.get_time()," ",str(volume))
self.stop()
break
def stopSound(self):
self.oktostop = True
def build_samples(self):
Fs = get_init()[0]
f = self.frequency
sample = Fs/f
x = np.arange(sample)
# Sine wave
#y = 0.5*np.sin(2*np.pi*f*x/Fs)
# Square wave
y = 0.5*sg.square(2*np.pi*f*x/Fs)
# Pulse wave
#sig = np.sin(2 * np.pi * x)
#y = 0.5*sg.square(2*np.pi*f*x/Fs, duty=(sig + 1)/2)
# Sawtooth wave
#y = 0.5*sg.sawtooth(2*np.pi*f*x/Fs)
# Triangle wave
#y = 0.5*sg.sawtooth(2*np.pi*f*x/Fs,0.5)
# White noise
#y = 0.5*np.random.uniform(-1.000,1.000,sample)
return y
pre_init(44100, -16, 2, 2048)
pygame.init()
screen = pygame.display.set_mode((480, 320))
pygame.mouse.set_visible(False)
CLK = 5
MISO = 6
MOSI = 13
CS = 12
mcp = Adafruit_MCP3008.MCP3008(clk=CLK, cs=CS, miso=MISO, mosi=MOSI)
Asec = 1.0
Dsec = 1.0
Ssec = 1.0
Rsec = 1.0
matrix0 = Adafruit_Trellis.Adafruit_Trellis()
trellis = Adafruit_Trellis.Adafruit_TrellisSet(matrix0)
NUMTRELLIS = 1
numKeys = NUMTRELLIS * 16
I2C_BUS = 1
trellis.begin((0x70, I2C_BUS))
# light up all the LEDs in order
for i in range(int(numKeys)):
trellis.setLED(i)
trellis.writeDisplay()
time.sleep(0.05)
# then turn them off
for i in range(int(numKeys)):
trellis.clrLED(i)
trellis.writeDisplay()
time.sleep(0.05)
posRecord = {'attack': [], 'decay': [], 'sustain': [], 'release': []}
octaval = {'A':False,'B':False,'C':False}
pitch = 0
tone = None
old_tone = None
note = None
volume = 0
#m = alsaaudio.Mixer('PCM')
#mastervol = m.getvolume()
sounds = {}
values = [0]*8
oldvalues = [0]*8
font = pygame.font.SysFont("comicsansms", 22)
while True:
fps.tick_busy_loop(FRAMERATE)
#print(fps.get_time())
update = False
#m.setvolume(int(round(MCP3008(4).value*100)))
#mastervol = m.getvolume()
values = [0]*8
for i in range(8):
# The read_adc function will get the value of the specified channel (0-7).
values[i] = mcp.read_adc(i)/1000
if values[i] >= 1:
values[i] = 1
# Print the ADC values.
#print('| {0:>4} | {1:>4} | {2:>4} | {3:>4} | {4:>4} | {5:>4} | {6:>4} | {7:>4} |'.format(*values))
#print(str(pygame.mixer.Channel(0).get_busy())+" "+str(pygame.mixer.Channel(1).get_busy())+" "+str(pygame.mixer.Channel(2).get_busy())+" "+str(pygame.mixer.Channel(3).get_busy())+" "+str(pygame.mixer.Channel(4).get_busy())+" "+str(pygame.mixer.Channel(5).get_busy())+" "+str(pygame.mixer.Channel(6).get_busy())+" "+str(pygame.mixer.Channel(7).get_busy()))
Sval = values[2]*Ssec
Aval = values[0]*Asec
if Sval == 1:
Dval = 0
else:
Dval = values[1]*Dsec
if Sval < MINSEC:
Rval = 0
else:
Rval = values[3]*Rsec
if Aval > 0:
if values[4] <= MINSEC: values[4] = MINSEC
Acurve = [round(values[4]*4,3),round(100/pow(Aval,(values[4]*4)),3)]
else:
Acurve = False
if Dval > 0:
if values[5] <= MINSEC: values[5] = MINSEC
Dcurve = [round(values[5]*4,3),round(((Sval*100)-100)/pow(Dval,(values[5]*4)),3)]
else:
Dcurve = False
Shold = values[6]*4*Ssec
if Rval > 0 and Sval > 0:
if values[7] <= MINSEC: values[7] = MINSEC
Rcurve = [round(values[7]*4,3),round(-Sval*100/pow(Rval,(values[7]*4)),3)]
else:
Rcurve = False
if update:
screen.fill((0, 0, 0))
scrnvals = ["A: "+str(round(Aval,2))+"s","D: "+str(round(Dval,2))+"s","S: "+str(round(Sval,2)),"R: "+str(round(Rval,2))+"s","H: "+str(round(Shold,2))+"s","ENV: "+str(round(Aval,2)+round(Dval,2)+round(Shold,2)+round(Rval,2))+"s"]
for line in range(len(scrnvals)):
text = font.render(scrnvals[line], True, (0, 128, 0))
screen.blit(text,(60*line+40, 250))
# Width of one second in number of pixels
ASCALE = 20
DSCALE = 20
SSCALE = 20
RSCALE = 20
if Aval >= MINSEC:
if Aval <= 1:
ASCALE = 80
else:
ASCALE = 20
# Attack
for yPos in range(0,101):
xPos = round(pow((yPos/Acurve[1]),(1/Acurve[0]))*ASCALE)
posRecord['attack'].append((int(xPos) + 40, int(-yPos) + 130))
if len(posRecord['attack']) > 1:
pygame.draw.lines(screen, DARKRED, False, posRecord['attack'], 2)
if Dval >= MINSEC:
if Dval <= 1:
DSCALE = 80
else:
DSCALE = 20
# Decay
for yPos in range(100,round(Sval*100)-1,-1):
xPos = round(pow(((yPos-100)/Dcurve[1]),(1/Dcurve[0]))*DSCALE)
#print(str(yPos)+" = "+str(Dcurve[1])+"*"+str(xPos)+"^"+str(Dcurve[0])+"+100")
posRecord['decay'].append((int(xPos) + 40 + round(Aval*ASCALE), int(-yPos) + 130))
if len(posRecord['decay']) > 1:
pygame.draw.lines(screen, DARKGREEN, False, posRecord['decay'], 2)
# Sustain
if Shold >= MINSEC:
for xPos in range(0,round(Shold*SSCALE)):
posRecord['sustain'].append((int(xPos) + 40 + round(Aval*ASCALE) + round(Dval*DSCALE), int(100-Sval*100) + 30))
if len(posRecord['sustain']) > 1:
pygame.draw.lines(screen, DARKYELLOW, False, posRecord['sustain'], 2)
if Rval >= MINSEC:
if Rval <= 1:
RSCALE = 80
else:
RSCALE = 20
# Release
for yPos in range(round(Sval*100),-1,-1):
xPos = round(pow(((yPos-round(Sval*100))/Rcurve[1]),(1/Rcurve[0]))*RSCALE)
#print(str(xPos)+" = (("+str(yPos)+"-"+str(round(Sval*100))+")/"+str(Rcurve[1])+")^(1/"+str(Rcurve[0])+")")
posRecord['release'].append((int(xPos) + 40 + round(Aval*ASCALE) + round(Dval*DSCALE) + round(Shold*SSCALE), int(-yPos) + 130))
if len(posRecord['release']) > 1:
pygame.draw.lines(screen, DARKBLUE, False, posRecord['release'], 2)
posRecord = {'attack': [], 'decay': [], 'sustain': [], 'release': []}
pygame.display.update()
tone = None
pitch = 0
time.sleep(MINSEC)
# If a button was just pressed or released...
if trellis.readSwitches():
# go through every button
for i in range(numKeys):
# if it was pressed, turn it on
if trellis.justPressed(i):
print('v{0}'.format(i))
trellis.setLED(i)
if i == 0:
octaval['A'] = True
elif i == 4:
octaval['B'] = True
elif i == 8:
octaval['C'] = True
else:
pitch = buttons[i]
button = i
# if it was released, turn it off
if trellis.justReleased(i):
print('^{0}'.format(i))
trellis.clrLED(i)
if i == 0:
octaval['A'] = False
elif i == 4:
octaval['B'] = False
elif i == 8:
octaval['C'] = False
else:
sounds[i].stopSound()
# tell the trellis to set the LEDs we requested
trellis.writeDisplay()
octa = ''
if octaval['A']:
octa += 'A'
if octaval['B']:
octa += 'B'
if octaval['C']:
octa += 'C'
if octa == '':
octa = 'BASE'
if pitch > 0:
tone = FREQ['C0']*pow(2,int(octaves[octa]))*pitch
if tone:
sounds[button] = Note(tone)
_thread.start_new_thread(sounds[button].playSound,(Aval, Dval, Sval, Rval, Acurve, Dcurve, Shold, Rcurve, fps))
print(str(tone))
GPIO.cleanup()
最佳答案
您目前正在做的是发出声音并放弃所有控制，直到播放了该声音。此处的一般方法是更改该值并一次处理一个样本，然后将其推入缓冲区(该缓冲区定期播放)。该样本将是您所有声音/信号的总和。这样，您可以为每个样本决定是否要触发新声音，并且可以决定在演奏音符时演奏音符多长时间。一种实现方法是安装一个计时器，如果您希望48kHz的采样率，则每1/48000秒触发一次回调函数。
如果您需要处理很多声音，但不能为一个声音使用一个线程，那么仍然可以使用多线程进行并行处理，这在我看来是过大了。是否必要，取决于您执行多少过滤/处理以及程序的有效/无效。
例如
sample_counter = 0
output_buffer = list()
def callback_fct():
pitch_0 = 2
pitch_1 = 4
sample_counter += 1 #time in ms
signal_0 = waveform(sample_counter * pitch_0)
signal_1 = waveform(sample_counter * pitch_1)
signal_out = signal_0 * 0.5 + signal_1 *0.5
output_buffer.append(signal_out)
return 0
if __name__ == "__main__":
call_this_function_every_ms(callback_fct)
play_sound_from_outputbuffer() #plays sound from outputbuffer by popping samples from the beginning of the list.
这样的事情。 Waveform()函数会根据实际时间乘以所需的音高为您提供采样值。在C语言中，您将使用指针完成所有操作，在Wavetable的末尾溢出，因此您将不必处理问题，即何时应重置sample_counter而不会出现波形毛刺(它将真正成为现实)不久)。但我敢肯定，对此还有更多“ python 般”的方法。使用更底层语言进行此操作的另一个很好的理由是速度。一旦涉及到真正的DSP，就将计算处理器的时钟节拍。那时python可能有太多的开销。