Sound generation pygame examples.
Here's a few sound generation examples with pygame (and no numpy/scipy).
If there's interest I'll expand this into a bigger example? Let me know.
All the basics for making a music program (sampler/synth).
- some sample rate conversion,
- bit rate conversion
- tone generation using generators (square wave)
- python arrays used as buffers for pygame.Sound (zero copy).
""" Some examples for generating and converting sounds for pygame. Python 2.7, 3.6 Shows: - a simple 'square wave' generated - resampling sample rates (eg, 8363 to 44100) - using built in python array for making pygame.Sound samples. - samples at different bit sizes - converting from signed 8 to signed 16bit - how initializing the mixer changes what samples Sound needs. - Using the python stdlib audioop.ratecv for sample rate conversion. Square Wave https://en.wikipedia.org/wiki/Square_wave MOD (file format) https://en.wikipedia.org/wiki/MOD_(file_format) pygame.mixer.get_init https://www.pygame.org/docs/ref/mixer.html#pygame.mixer.get_init pygame.Sound https://www.pygame.org/docs/ref/mixer.html#pygame.mixer.Sound array (python stdlib) https://docs.python.org/3/library/array.html wave (python stdlib) https://docs.python.org/3/library/wave.html audioop.ratecv (python stdlib) https://docs.python.org/3/library/audioop.html?highlight=audio#audioop.ratecv """ from array import array import pygame as pg class Tone(pg.mixer.Sound): """This generates a 'Square wave' with a generator. Then creates an array of samples, and passes that into pygame.Sound. """ def __init__(self, frequency, array_type, volume=.1): self.frequency = frequency if array_type == 'b': # we have to convert the 1 byte 'b' samples to 2 byte 'h'. samples = self.signed_char_to_signed_short( self.make_samples_b() ) elif array_type == 'h': samples = self.make_samples_h() else: raise ValueError('array_type not supported') pg.mixer.Sound.__init__(self, buffer=samples) self.set_volume(volume) def make_samples_b(self): """ Builds samples array between -127 and 127. Array type 'h'. """ mixer_frequency = pg.mixer.get_init()[0] mixer_format = pg.mixer.get_init()[1] period = int(round(mixer_frequency / self.frequency)) max_amplitude = 2 ** (abs(mixer_format) - 1) - 1 max_amplitude = int(max_amplitude / 256) # print(f'mixer_frequency:{mixer_frequency}, mixer_format:{mixer_format}') # print(f'period:{period}, max_amplitude:{max_amplitude}') # 'b' array is signed char, 1 byte # https://docs.python.org/3/library/array.html samples = array('b', (max_amplitude if time < period / 2 else -max_amplitude for time in range(period)) ) return samples def signed_char_to_signed_short(self, b_samples): """ Converts 1 byte signed char samples to 2 byte signed short. 127 to 32767 """ # just a simple linear conversion. factor = int(32767 / 127) return array('h', (sample * factor for sample in b_samples)) def make_samples_h(self): """ Builds samples array between -32767 snd 32767. Array type 'h'. """ mixer_frequency = pg.mixer.get_init()[0] mixer_format = pg.mixer.get_init()[1] period = int(round(mixer_frequency / self.frequency)) max_amplitude = 2 ** (abs(mixer_format) - 1) - 1 # print(f'mixer_frequency:{mixer_frequency}, mixer_format:{mixer_format}') # print(f'period:{period}, max_amplitude:{max_amplitude}') # 'h' array is signed short, 2 bytes # https://docs.python.org/3/library/array.html samples = array('h', (max_amplitude if time < period / 2 else -max_amplitude for time in range(period)) ) return samples class Sample(pg.mixer.Sound): """ For playing a sample. Takes a file, and reads it in as 8bit signed data. Then converts it to the 16bit signed size the pygame.mixer needs. """ def __init__(self, fname, volume=.1): with open(fname, 'rb') as f: samples = self.signed_char_to_signed_short ( array('b', f.read()) ) pg.mixer.Sound.__init__(self, buffer=samples) self.set_volume(volume) def signed_char_to_signed_short(self, b_samples): """ Converts 1 byte signed char samples to 2 byte signed short. 127 to 32767 """ # just a simple linear conversion. import time t0=time.time() factor = int(32767 / 127) samples = array('h', ( max(sample, -127) * factor if sample < 0 else min(sample, 127) * factor for sample in b_samples)) t1=time.time() print(t1-t0) return samples def fetch_example_mod_file(mod_fname): """ Grab a file that has a sound samples in it from the net. 'MOD is a computer file format used primarily to represent music, and was the first module file format. MOD files use the ".MOD" file extension, except on the Amiga which doesn't rely on filename extensions, instead it reads a file's header to determine filetype. A MOD file contains a set of instruments in the form of samples, a number of patterns indicating how and when the samples are to be played, and a list of what patterns to play in what order.' https://en.wikipedia.org/wiki/MOD_(file_format) """ import os url = 'https://api.modarchive.org/downloads.php?moduleid=101996' if not os.path.exists(mod_fname): import urllib2 print ('Fetching %s .mod into file: %s' % (url, mod_fname)) data = urllib2.urlopen(url).read() with open(mod_fname, 'w') as modf: modf.write(data) def resample(mod_fname): """ An example of resampling audio to a different framerate. eg, from 8363 one byte samples per second to 44100 two byte samples per second. """ import audioop import wave from io import BytesIO in_framerate = 8363 in_sampwidth = 1 in_nchannels = 1 out_framerate = 44100 num_seconds = 5 with open(mod_fname, 'rb') as f: # Throw away the start data of this mod file. # Better samples later on. f.read(8363*2) in_frame_data = f.read(in_framerate * num_seconds) # https://docs.python.org/3/library/audioop.html?highlight=audio#audioop.ratecv newfragment, newstate = audioop.ratecv( in_frame_data, in_sampwidth, in_nchannels, in_framerate, out_framerate, None) # print(f'len(newfragment):{len(newfragment)}') # A perfect conversion is not possible, because the sample # rates do not divide equally. However, the number # of samples should be close. assert (out_framerate * num_seconds) - len(newfragment) < 10 pg.mixer.Sound(buffer=newfragment).play(-1) # TODO: # Converting between modo and stereo? # audioop.tomono and audioop.tostereo # https://docs.python.org/3/library/audioop.html?highlight=audio#audioop.tomono # How to draw a wave form? # using pygame.draw.lines transforming audio into # Surface space. # Meaning, scaling audio samples into a particular # sized part of the screen. # More sound generator types. # Saw tooth. if __name__ == "__main__": # https://www.pygame.org/docs/ref/mixer.html#pygame.mixer.init pg.mixer.pre_init(44100, -16, 1, 1024) pg.init() pg.display.set_caption('Playing square wave, 808 frequency') pg.display.set_mode((320, 200)) mod_fname = 'outrun_3.mod' fetch_example_mod_file(mod_fname) # play on repeat, -1 means loop indefinitely. # https://www.pygame.org/docs/ref/mixer.html#pygame.mixer.Sound.play if 0: Tone(frequency=808, array_type='b').play(-1) if 0: try: Sample(mod_fname).play(-1) except IOError: print ('no %s' % mod_fname) if 0: pg.mixer.music.load(mod_fname) pg.mixer.music.play() if 1: resample(mod_fname) going = True while going: for e in pg.event.get(): if e.type in [pg.QUIT, pg.KEYDOWN]: going = False
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