import numpy as np
 
def speedx(sound_array, factor):
  """ 将音频速度乘以任意系数`factor` """
  indices = np.round( np.arange(0, len(snd_array), factor) )
  indices = indices[indices < len(snd_array)].astype(int)
  return sound_array[ indices.astype(int) ]

def stretch(sound_array, f, window_size, h):
  """ 将音频按系数`f`拉伸 """
 
  phase = np.zeros(window_size)
  hanning_window = np.hanning(window_size)
  result = np.zeros( len(sound_array) /f + window_size)
 
  for i in np.arange(0, len(sound_array)-(window_size+h), h*f):
 
    # 两个可能互相重叠的子数列
    a1 = sound_array[i: i + window_size]
    a2 = sound_array[i + h: i + window_size + h]
 
    # 按第一个数列重新同步第二个数列
    s1 = np.fft.fft(hanning_window * a1)
    s2 = np.fft.fft(hanning_window * a2)
    phase = (phase + np.angle(s2/s1)) % 2*np.pi
    a2_rephased = np.fft.ifft(np.abs(s2)*np.exp(1j*phase))
 
    # 加入到结果中
    i2 = int(i/f)
    result[i2 : i2 + window_size] += hanning_window*a2_rephased
 
  result = ((2**(16-4)) * result/result.max()) # 归一化 (16bit)
 
  return result.astype('int16')

def pitchshift(snd_array, n, window_size=2**13, h=2**11):
  """ 将一段音频的音高提高``n``个半音 """
  factor = 2**(1.0 * n / 12.0)
  stretched = stretch(snd_array, 1.0/factor, window_size, h)
  return speedx(stretched[window_size:], factor)

from scipy.io import wavfile
 
fps, bowl_sound = wavfile.read("bowl.wav")
tones = range(-25,25)
transposed = [pitchshift(bowl_sound, n) for n in tones]

import pygame
 
pygame.mixer.init(fps, -16, 1, 512) # 太灵活了 <img src="http://python.jobbole.com/wp-includes/images/smilies/icon_wink.gif" alt=";)" class="wp-smiley">
screen = pygame.display.set_mode((640,480)) # 设置焦点
 
# 得到键盘的键位的正确顺序的列表
# ``keys`` 如 ['Q','W','E','R' ...] 一样排列
keys = open('typewriter.kb').read().split('\n')
 
sounds = map(pygame.sndarray.make_sound, transposed)
key_sound = dict( zip(keys, sounds) )
is_playing = {k: False for k in keys}
 
while True:
 
  event = pygame.event.wait()
 
  if event.type in (pygame.KEYDOWN, pygame.KEYUP):
    key = pygame.key.name(event.key)
 
  if event.type == pygame.KEYDOWN:
 
    if (key in key_sound.keys()) and (not is_playing[key]):
      key_sound[key].play(fade_ms=50)
      is_playing[key] = True
 
    elif event.key == pygame.K_ESCAPE:
      pygame.quit()
      raise KeyboardInterrupt
 
  elif event.type == pygame.KEYUP and key in key_sound.keys():
 
    key_sound[key].fadeout(50) # 停止播放并50ms淡出
    is_playing[key] = False