@classmethod
def _time_position(cls, duration, frames_start=5, frames_end=95, frames_gap=10
    ):
    """Calculate time positions."""
    duration = float(duration)
    time_step = duration * frames_gap / 100
    start_time = duration * frames_start / 100
    end_time = duration * frames_end / 100 + 0.01
    number_of_frames = (frames_end - frames_start) / frames_gap + 1
    return {'duration': duration, 'start_time': start_time, 'end_time':
        end_time, 'time_step': time_step, 'number_of_frames': number_of_frames}
