procedural.py 文件源码

def _generate_data(self, num_bytes, offset):
        if self._bytes_per_sample == 1:
            start = offset
            samples = num_bytes
            bias = 127
            amplitude = 127
            data = (ctypes.c_ubyte * samples)()
        else:
            start = offset >> 1
            samples = num_bytes >> 1
            bias = 0
            amplitude = 32767
            data = (ctypes.c_short * samples)()
        step = self.frequency * (math.pi * 2) / self.audio_format.sample_rate
        envelope = self._envelope_array
        env_offset = offset // self._bytes_per_sample
        for i in range(samples):
            data[i] = int(math.sin(step * (i + start)) *
                          amplitude * envelope[i+env_offset] + bias)
        return data