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Originally Posted by Tribuna DelCavo
Bandwidth difference is significant buy how are they getting better quality?
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I never said that either Sky or NTL would get better quality. Bandwidth is the only significant matter really, as, AFAIK, Sky have relatively limited bandwidth available (compare to Cable).
The only way Quality might come into it is if someone has to convert from one compression to the other at some point. Say, for instance, a broadcaster encodes as an MPEG 2 file and sends to all the platforms. Sky would have to recode the program, so there would be a slight quality loss on that platform. If the broadcaster encodes as MPEG 4, then sends that, NTL and Telewest would have to recode as MPEG, so there would be a slight quality loss on Cable. Similarly, if the broadcaster sends an MPEG 2 programme to Sky (who recode as MPEG 4), then Cable recieves the Sky broadcast and recodes again as MPEG 2.
Another area where quality loss comes in is simply that most Audio/Video compression system are "lossy". Audio/Visual compression systems work by not encoding data that doesn't change from frame to frame, and also not encoding audio frequencies outside the range of human hearing. Thus, they lose that data. The trick is not to alter the sound or video we percieve too much. Data compression systems (such as ZIP) have to reproduce a perfect copy of a file, so they work differently.
H.264 is a very good compression system. *Much* better than MPEG 2. It's more efficient at keeping the sound and video apparently the same, while compressing them..