Hi list, I'm having trouble playing sounds (generated from arrays) as stereo sounds. Creating a sound and copying it to two channels seems to double the frequency.
The following script (see also here: http://pastebin.com/qqZbJavf ) should make it more clear. It constructs a simple 400Hz sine wave and plays it as a mono sound (nchannels = 1) or duplicates the array and plays it as a stereo sound (nchannels = 2). In the second case, however, the tone that is played is an 800Hz tone instead of a 400Hz one... This seems not to happen on Windows, I encountered the problem on ArchLinux and Ubuntu 11.10 (both having pygame 1.9.1). import numpy as np import pygame as pg import time frequency, samplerate, duration = 400, 44100, 20000 nchannels = 1 # change to 2 for stereo pg.mixer.pre_init(channels=nchannels, frequency=samplerate) pg.init() sinusoid = (2**15 - 1) * np.sin(2.0 * np.pi * frequency * \ np.arange(0, duration) / float(samplerate)) samples = np.array(sinusoid, dtype=np.int16) if nchannels > 1: #copy mono signal to two channels samples = np.tile(samples, (nchannels, 1)).T sound = pg.sndarray.make_sound(samples) sound.play() time.sleep(duration/float(samplerate))
