def process(self, frames=None, eod=False):
Process input frames and return a (output_frames, eod) tuple.
        Both input and output frames are 2D numpy arrays, where columns are
        channels, and containing an undetermined number of frames.  eod=True
        means that the end-of-data has been reached.

        Output-only processors (such as decoders) will raise an exception if the
        frames argument is not None. All processors (even encoders) return data,
        even if that means returning the input unchanged.

        Warning: it is required to call setup() before this method.