elphyio.py 文件源码

def get_tag_data(self, episode, tag_channel):
        #memorise some useful properties
        block = self.episode_block(episode)
        sample_size = self.sample_size(episode, tag_channel)
        sample_symbol = self.sample_symbol(episode, tag_channel)

        #create a bit mask to define which
        #sample to keep from the file
        channel_mask = self.create_channel_mask(episode)
        bit_mask = self.create_bit_mask(channel_mask, 1)

        #get bytes from the file
        data_block = self.data_blocks[episode - 1]
        n_bytes = data_block.size
        self.file.seek(data_block.start)
        databytes = np.frombuffer(self.file.read(n_bytes), '<i1')

        #detect which bits keep to recompose the tag
        ep_mask = np.ones(n_bytes, dtype=int)
        np.putmask(ep_mask, ep_mask, bit_mask)
        to_keep = np.where(ep_mask > 0)[0]
        raw = databytes.take(to_keep)
        raw = raw.reshape([len(raw) / sample_size, sample_size])

        #create a recarray containing data
        dt = np.dtype(numpy_map[sample_symbol])
        dt.newbyteorder('<')
        tag_mask = 0b01 if (tag_channel == 1) else 0b10
        y_data = np.frombuffer(raw, dt) & tag_mask
        x_data = np.arange(0, len(y_data)) * block.dX + block.X0
        data = np.recarray(len(y_data), dtype=[('x', b_float), ('y', b_int)])
        data['x'] = x_data
        data['y'] = y_data

        return data