Re: Digital TV

[Raymond <Reb.barnett@xxxxxxx>]

> The question was for a IRD that plugged directly into PC or other MPEG
> recording device.  Which I assumed to be receiving off air,
> either Sat or
> Terrestrial.  This being the case then the bandwidth per channel is on
> average 4Mb/s which includes text, audio, programme related
> data etc.  This
> does not proved a good quality picture.  An analogue channel
> is at least in
> frequency terms about 27MHz (compared to a single 4Mb/s
> channel of about
> 3Mhz) so inherently better quality, specially as it is hardly
> compressed.

Except that there is no technological reason why Sky only allocate 4Mb/s
to a channel. They do it because they can get away with it, at the
moment. Few people can spot digital artefacts until you point them out
to them and they know what to look for (few people I know are bothered
by ghosting until you point it out and suggest they don't have to put up
with it). Once digital has a greater general acceptance people will
demand higher quality and I'm sure Sky will be only to happy to charge
for 'premium' channel to meet this demand, but they won't until there is
a demand. I'm no audio expert, and when I first heard a CD I couldn't
really spot the difference between a CD and a good tape recording. Now I
can. Just because something is compressed doesn't make it inferior
quality, so comparing a 27MHz analogue signal with a 3Mhz digital
compressed signal is largely meaningless unless you also know the degree
of compression and the quality of encoder used (currently too much and
too low).

My interest in the medium stems from the fact that I can do more with a
digital data stream using my PC, and the fact that the quality of even
good video recorders is awful.

Ray.

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