On May 8, 3:28=A0pm, Alan F <afigga...@[EMAIL PROTECTED]
> wrote:
> Guy wrote:
> > There's no reason in the world that the cable companies must send
a digital
> > broadcast over the cable as a digital signal. Just as a converter
box
> > converts a digital signal to analog and then sends it to your set
over the
> > coax connector, so too can a cable system do the conversion at
their
> > headquarters and send it as an analog signal from there to your
house.
>
> =A0 There are very good reasons to go all digital - bandwidth! Each
analog
> NTSC channel takes up 6 MHz of bandwidth. In that same frequency
space,
> they can insert a digital QAM-256 signal with a 38,4 Mbps data rate
> which can carry 9 to 10 high quality digital SD channels or 2 full
> bandwidth HD channels (or 3 over-compressed HD channels as Comcast
has
> started to do).
>
> =A0 Analog NTSC is a major bandwidth hog. The bandwidth crunch is
between
> your house and the head end. With 135 channels available in a
typical
> 860 MHz system, a typical cable line-up of 70+ analog channels
takes up
> a huge chunk of the available bandwidth. By turning off 10 analog
> channels and replacing them with digital QAM channels, the cable
company
> can add 90 SD 480i channels of better picture quality or 20 HD
channels
> with 5.1 sound. Analog NTSC has served us well, but its' time has
passed.
>
> =A0 Alan F
In LA, KABC-DT typically runs 8-12 megabit HD channels, KTTV (Fox)
runs 15 megs, KCBS 15-16 so if the cable company shrinks to 12 megs,
who would notice? Also, until 2 years ago, Fox LA ran 8 megabits for
everything. KCET HD frequently dips below 7 _and_ cross converts to
720p
GG
|
