def find_skipped_frames(lines, step=1):
    """
    Check if there are skipped frames based on status line reading.

    `step` specifies expected index step between neighboring frames.

    Return list ``[(idx, skipped)]``, where `idx` is the index after which `skipped` frames were skipped.
    """
    dfs=(lines[1:,1]-lines[:-1,1])%(2**24) # the internal counter is only 24-bit
    skipped_idx=(dfs!=step)
    skipped_idx=skipped_idx.nonzero()[0]
    return list(zip(skipped_idx,dfs[skipped_idx])) if len(skipped_idx) else []