OT: Tuning Cable

[Kenneth Brody]

Quoting Jay R. Ashworth (Wed, 13 Jul 2005 18:20:49 -0400):

> On Tue, Jul 12, 2005 at 09:58:14PM -0400, Brian K. White wrote:
> > My gripe was about how it takes 3 to 5 seconds on average, rarely less
> > than 2 full seconds, some times 10 or more in special cases+, just to
> > change the channel on a modern digital cable box, and how that is a
> > huge loss in goodness from older tv's where it was _instantaneous_ on
> > the oldest analog mchanical pre-cable tuner knob. 3 to 5 seconds to
> > change a channel? When I've got 200 channels to cycle through?
> > Ridiculous!
>
> Most cable converters can lock up to the analog channels almost
> immediately; it's the digital (MPEG) channels that take a couple
> seconds; mostly because they use Long GOP encoding to save bandwidth,
> and you have to wait until you get a full-frame.

But, even the analog cable signals are converted from digital somewhere
upstream.  It makes for some "interesting" effects at times when it
misses the full-frame signal, and continues using the in-between frames
as updates.  (From the looks of it, it appears that interim frames are
sent as deltas from the previous frame?)  Of course, it corrects itself
several seconds later once it gets the next full-frame data, but in the
meantime, you get one messed up display.  (Or, messed up blocks, when
it misses one of the interim frames.)

So, even analog cable boxes are affected by digital, though they do
get the channel immediately.

--
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