procedural.py 文件源码

def _generate_data(self, num_bytes, offset):
        # XXX TODO consider offset
        if self._bytes_per_sample == 1:
            samples = num_bytes
            value = 127
            maximum = 255
            minimum = 0
            data = (ctypes.c_ubyte * samples)()
        else:
            samples = num_bytes >> 1
            value = 0
            maximum = 32767
            minimum = -32768
            data = (ctypes.c_short * samples)()
        step = (maximum - minimum) * self.frequency / self._sample_rate
        envelope = self._envelope_array
        env_offset = offset // self._bytes_per_sample
        for i in range(samples):
            value += step
            if value > maximum:
                value = minimum + (value % maximum)
            data[i] = int(value * envelope[i+env_offset])
        return data