Re: AKICIF: Television Formats

In <ge5jpj$nhl$1@xxxxxxxxxxxxxxxx> "Keith F. Lynch" <kfl@xxxxxxxxxxxxxx> writes:

Torbjorn Lindgren <tl@xxxxxxxxxxxx> wrote:
Keith F. Lynch <kfl@xxxxxxxxxxxxxx> wrote:
Bad media can damage the reading hardware? That was true for
devices that physically contacted the media, such as record and
tape players and tape drives, but how can it be true for any kind
of optical discs?

No, "bad" hardware working "well enough" for a period before
getting progressively worse. The "damage" mostly comes from cheap
components deteriorating (partly due to the designer not using
enough margins) and optical alignment issues (due to insufficient
stiffness, again $$$). Like I said, it's much better now presumably
due to a lot of experience on the builders part.

My CD player skips a lot on the first one or two tracks of CDs, but
only if it's been on for less than an hour, or if the temperature in
my apartment is under 80 F. Any idea what could account for this?
Is this a typical failure pattern?

It's often condensation on the lens, although the heat usually evaporates
the moisture faster than an an hour.

I find it surprising how well most DVD readers can read even
somewhat damaged dvd (without polishing & optical filling in). From
your description it sounds like it may not even have been noticed by
most readers. It's also worth remembering that "noticed" may well
mean simply falling back to a lower read speed, not delayed data or
actual visible problems.

Don't all DVD players run at the same speed, except when you're
fast-forwarding?

No -- they often try to read-ahead to buffer in case the error correction
needs to try to fix the errors it detects.

Mine sometimes freezes for half a second, even with perfectly clean
discs. This invariably means that in a few seconds it will freeze for
several seconds, then a few seconds later, will freeze indefinitely.
When frozen indefinitely, it will repeatedly spin the disc down, then
spin it up to very high speeds, then spin it down again, etc., as if
it were trying to recover, which it never succeeds at doing. In this
mode it will ignore the "off" button; I have to pull the plug. If I
wait more than a minute before plugging it back in, it will probably
be fine. If I wait less time, the disc may refuse to load.

It sounds like there's a bug in the code running in the player. Early DVD
players were buggier than recent ones.

Even 1x is enough for normal play and they're often spun slower than
the maximum speed (say perhaps 4-8x) when viewing DVDs anyway to
reduce vibration & noise.

Why would it ever spin faster than 1x except when you're fast-
forwarding or searching?

Error-correction buffering. (I'm assuming it's a standalone player, not a
drive connected to a computer.)

I suspect that the usually smaller antennas needed for digital
reception is a lot less sensitive to direction, it's what I would
expect from a smaller antenna anyway (but I'm not an expert on
antennas).

Digital TV is mostly UHF. UHF antennas are much more directional
than VHF.

They're generally loops, rather than rabbit ears.

Also, you can find out the proper heading and use a compass, that's
how the big old antenna (long gone, for analog) in the case I talked
about before got pointed in roughly the right direction before the
fine tuning (a large roof mounted multi-element antenna, fairly
directional and not fun to adjust).

I was thinking mostly of rabbit ears, which often give the best
reception when placed in some very unlikely looking positions, ones
with no obvious correlation with the direction of the transmitter.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.

Ben
--
Ben Yalow ybmcu@xxxxxxxxx
Not speaking for anybody
.

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