io_methods.py 文件源码

def _wav2array(nchannels, sampwidth, data):
        """data must be the string containing the bytes from the wav file."""
        num_samples, remainder = divmod(len(data), sampwidth * nchannels)
        if remainder > 0:
            raise ValueError('The length of data is not a multiple of '
                             'sampwidth * num_channels.')
        if sampwidth > 4:
            raise ValueError("sampwidth must not be greater than 4.")

        if sampwidth == 3:
            a = np.empty((num_samples, nchannels, 4), dtype = np.uint8)
            raw_bytes = np.fromstring(data, dtype = np.uint8)
            a[:, :, :sampwidth] = raw_bytes.reshape(-1, nchannels, sampwidth)
            a[:, :, sampwidth:] = (a[:, :, sampwidth - 1:sampwidth] >> 7) * 255
            result = a.view('<i4').reshape(a.shape[:-1])
        else:
            # 8 bit samples are stored as unsigned ints; others as signed ints.
            dt_char = 'u' if sampwidth == 1 else 'i'
            a = np.fromstring(data, dtype='<%s%d' % (dt_char, sampwidth))
            result = a.reshape(-1, nchannels)
        return result