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Originally Posted by ayh20  It's certainly not "impossible", impractical almost certainly ... I'd be intrigued on what sort of bit rate that would be required. 30mb ? 40mb ?
But what about 3D TV ? Isn't that going to require very high bit rates ? (Personally i don't get the point of 3D TV ....)
You mention rapid movement .... a good example of what's wrong with BBC HD was a recent music show ... the background was static and crystal clear, the artist was bouncing in time with music and blurred out of recognition.. for pete's sake they only have to transmit the bit that's moving ! And it can't even cope with that ... duh |
It's impossible to exactly represent an analogue waveform by digitising it. Digitising works by splitting up an analogue waveform into little chunks of square waves the higher the sample rate the smaller the square wave chunks the closer the waveform get's to the original signal but it can't by definition be 100% accurate. Once digitised to transmit it has to be compressed using mpeg compression which creates a full frame of data and sub frames of data containing difference info which allows the decoder to rebuild the original frames. The faster the motion the higher the bitrate required to follow the motion. This process is also inherently lossy so again it's not possible to create a 100% accurate representation of the original source.
A lossless system does exist it uses a single uhf carrier to carry a single TV channel fm modulating the carrier signal using the original waveform. At the receiving end (given a good interference free signal) the uhf carrier is generated locally subtracted from the transmitted carrier leaving only the original waveform. It's known as analogue TV and it's currently being shut down so that dozens of inferior quality transmissions can be shoehorned onto the same uhf carriers using digital multiplexing. Result less uhf band required for TV so the government can flog of the spare capacity.