HD TV
The most important idea in creating an HD TV is figuring out how to transmit digital information in bits that retain the most visual clarity when it is transferred to the TV screen. Older analogue TVs sent signals every 50 msec that encoded the color for every pixel in the screen for every change of frame, but because the HD TV signal also encodes for intensity, movement, and color, HD TV cannot transmit information the same way. If it did, 50 GHz would be sent for every signal- that’s a lot of digital information! Therefore the signal is condensed and broken into what are called frames. First, an i-frame is sent once every second. An i-frame encodes for all the color and intensities that every pixel should display for the next second. Then, a b-frame is sent about 20 times a second that encodes for image movement by directing points of light in a series of vectors. In coordination with b-frames, m-frames are sent to predict where images will go by the time the next i-frame is sent. To illustrate what these frames do, imagine a white TV screen with a red dot in the middle, where the red dot is shrinking towards the center. The i-frame tells the TV that there is a white screen because the white screen is constant until the next i-frame. The b-frame tells that some of the pixels change to red, and that the movement follows certain trajectories toward the center. Finally, the m-frame predicts where the edges of the red circle will be by the next second. Though this example is extremely elementary, what you get with the division of information transmission through these frames are finely tuned edges that make depth perception on the screen much more defined that a regular analogue TV.
But what really makes the image so clear is how are brain works in sync with the HD TV. Visual acuity depends on edge detection, and thanks to the structure of the center-surround ganglion cells, our brain is able to ‘see’ the football going across the HD TV screen. In addition to eye structure, our brain is able to pick apart many aspects of light movement and depth perception in the visual cortex, which gives watching TV its appeal. Engineers spent countless hours trying to figure out just how our vision is maximally stimulated by certain projections of light, and what they came up with so far is the HD TV. Cisco and its associates that specialize in producing TV screens have done countless research hours on how our eyes perceive light. In one project, they looked at how different color intensity projections affect starring and blurring on the TV screen. Blue light has to be shown at three hundred times the intensity as red light because it takes a much higher energy of the 420 nm wavelength to be perceived by the eye. Therefore, when the different intensities are combined on the TV screen, a small percentage of people can detect blurring or starring effects on the screen. Cisco engineers has to understand what and how our eyes perceive in order to make sure that things like starring do not occur.
Another thing engineers have to understand is how rapid our brains can fill in the empty spaces between frames. The combinations of i-, b-, and m-frames carefully manipulate our visual sense- images on the TV are not actually as clearly defined as you think they are. Have you ever noticed how blurry the TV screen is whenever you pause a movie? Our brain picks up the images’ movement and color on the TV screen and imagines boundaries that make our perception much clearer than reality (at least in regards to what’s happening on the TV screen.) As our visual projections filter through the lateral geniculate nucleus, superior colliculus, and optic radiation to the primary cortex, our brain constantly picks up apart all the individual aspects of movement, color, depth, and shape to integrate our visual experience with other aspects of our senses. On top of understanding what is already there, our visual perception fills in the gaps between frames with what our brain believes is happening. The result is a fluid stream of visual output rather than a succession of visual frames, and because an HD TV separates color, from movement and shape, our brains are able to independently perceive color and movement more clearly, though we ‘see’ those two aspects as one indistinguishable unit of vision.
