Quote:
Originally Posted by grahamlthompson  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. |
Umm .... not quite what i meant Graham...
My assumption was that the images were captured on a high quality HD cameras (@HD resolution or higher) or cinema film formats (35mm ?), then edited/post production at native resolution. Therefore the limitations are in the capture/production end .... the transmission chain should then be completely transparent.
At the mpeg compression level, as you say, there are compromises that have to be made. It is perfectly possible to be lossless at this stage, but this requires silly bitrates. Compromises have to be made i know, but how can Sky get it right (the Gaza docu the other night was impressive) and the BBC quite so bad.
I want to see what the production team produced not the rubbish that the broadcaster transmitted. (any more than willing to pay extra for it ..
)