A high-definition television system is a system designed to allow viewing at about three times the picture height, such that the system is virtually, or nearly, transparent to the quality of portrayal that would have been perceived in the original scene or performance by a discerning viewer with normal visual acuity. Such factors include improved motion portrayal and improved perception of depth. A high-definition system generally implies in comparison with conventional television systems: spatial resolution in the vertical and horizontal directions of about twice that available in CCIR Red 601-2; any worthwhile improvements in temporal resolution beyond that achievable with CCIR Red 601-2; improved colour rendition; a wider aspect ratio; multichannel highfidelity sound.