Do you really like the way HDTV looks?

wbertram writes:

Gene E. Bloch wrote:
On 9/24/2006, Paul Ratcliffe posted this:

On Sun, 24 Sep 2006 08:20:56 -0700, Richard Crowley
wrote:

"Paul Ratcliffe" wrote ...

Gene E Bloch wrote:

I repate, in engineering, a dB figure is alwasys given with a
reference.


No it isn't. It depends if you are specifying an absolute level or a
relative one.


If you believe that, you should read this:

http://www.m-w.com/dictionary/decibel


I do believe it. That link didn't tell me anything I don't
already know.
What exactly is your point? You don't really seem to know what you're
talking about do you?


Decibels are used both as a measurement of ratio
(change) AND as a measurement of absolute level.

In the case of a ratio (change), no external reference
is needed.


Which was what I said before moron Gene E Bloch stuck his oar in and
contradicted.
I will contradict you again, since you are ... wrong.
You will (well, *you* probably won't - or can't) note that *all* of
the things you want to call "absolute", such as dBm, dBu, and so on
(such as mentioned by Richard Crowley), are defined with respect to
a reference value. In short, and for one example, dBm gives the
*ratio* of the measured quantity to 1 milliwatt.
I would recommend to anyone who is not too IQ impaired to look at
http://en.wikipedia.org/wiki/Decibel
Naturally, I absolve you of any requirement to look there. You may
if you wish, of course, although if you do, you mght have to accept
the risk of learning something. Somehow I'm not too worried for you
:-)


One Watt ( or 1mW, or 1uW) is an absolute. A multiple of an absolute
is also an absolute, i.e., 5 times 1W, or 5W is an absolute power
level of 5W. If one chooses to express 5 times 1W as 7dBW, then it is
still an absolute.

0dBW = 1 times 1W = 1W = An absolute power level of 1W!
7dBW = 5 times 1W = 5W = An absolute power level of 5W!

Hey guys,

I'm not even sure who's right and who's wrong anymore in this, but
one thing is for certain: there are times when decibels are used
for relative comparisons without any specific power level in mind.

For example, it is commonly known that 3 dB is twice the power,
and -3 dB is half power.

In audio it is commonly accepted that it takes about 10 dB for a
sound to be perceived as twice as loud (or half as loud).

But there are certain units that ARE absolute power levels, which
I think one or both of you have already mentioned. I think the
most common is dBm, which is a dB relative to 1 milliwatt. This
is used all the time in RF measurements. There are others, as
dBW, e.g.
--
% Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
%% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and
%%% 919-577-9882 % Verdi's always creepin' from her room."
%%%% % "Rockaria", *A New World Record*, ELO
http://home.earthlink.net/~yatescr

On 9/25/2006, wbertram posted this:

Gene E. Bloch wrote:
On 9/24/2006, Paul Ratcliffe posted this:

On Sun, 24 Sep 2006 08:20:56 -0700, Richard Crowley
wrote:

"Paul Ratcliffe" wrote ...

Gene E Bloch wrote:

I repate, in engineering, a dB figure is alwasys given with a
reference.


No it isn't. It depends if you are specifying an absolute level or a
relative one.


If you believe that, you should read this:

http://www.m-w.com/dictionary/decibel


I do believe it. That link didn't tell me anything I don't already know.
What exactly is your point? You don't really seem to know what you're
talking about do you?


Decibels are used both as a measurement of ratio
(change) AND as a measurement of absolute level.

In the case of a ratio (change), no external reference
is needed.


Which was what I said before moron Gene E Bloch stuck his oar in and
contradicted.


I will contradict you again, since you are ... wrong.

You will (well, *you* probably won't - or can't) note that *all* of the
things you want to call "absolute", such as dBm, dBu, and so on (such as
mentioned by Richard Crowley), are defined with respect to a reference
value. In short, and for one example, dBm gives the *ratio* of the measured
quantity to 1 milliwatt.

I would recommend to anyone who is not too IQ impaired to look at

http://en.wikipedia.org/wiki/Decibel

Naturally, I absolve you of any requirement to look there. You may if you
wish, of course, although if you do, you mght have to accept the risk of
learning something. Somehow I'm not too worried for you :-)


One Watt ( or 1mW, or 1uW) is an absolute. A multiple of an absolute is also
an absolute, i.e., 5 times 1W, or 5W is an absolute power level of 5W. If
one chooses to express 5 times 1W as 7dBW, then it is still an absolute.

0dBW = 1 times 1W = 1W = An absolute power level of 1W!
7dBW = 5 times 1W = 5W = An absolute power level of 5W!

Completely specious argument.

A signal at 0 dBW is a signal with a power level whose ratio to 1W is
1, so that signal is at 1 W.

A signal at 7 dBW is a signal with a power level whose ratio to 1W is 5
(well, 5.011...), so that signal is at just about 5 W.

Yes, the signals can be measured at absolute power levels by a power
meter, but the measurement *when expressed in dB* is still a ratio to a
reference value.

In your argument, the 7 dB indeed specifies a ratio of 5, as shown by
the fact that you yourself had to say "5 times 1W". To put it yet
another way, "times" expresses the "ratio" to the reference value.

For instance, "the ratio of 10 to 5 is 2" is a precise mathematical
equivalent to "10 equals 5 times 2".

I'm glad that several posters in this thread (such as Albert Manfredi)
understand decibels; I wish you all did.

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

On 9/25/2006, Randy Yates posted this:
wbertram writes:

Gene E. Bloch wrote:
On 9/24/2006, Paul Ratcliffe posted this:

On Sun, 24 Sep 2006 08:20:56 -0700, Richard Crowley
wrote:

"Paul Ratcliffe" wrote ...

Gene E Bloch wrote:

I repate, in engineering, a dB figure is alwasys given with a
reference.


No it isn't. It depends if you are specifying an absolute level or a
relative one.


If you believe that, you should read this:

http://www.m-w.com/dictionary/decibel


I do believe it. That link didn't tell me anything I don't
already know.
What exactly is your point? You don't really seem to know what you're
talking about do you?


Decibels are used both as a measurement of ratio
(change) AND as a measurement of absolute level.

In the case of a ratio (change), no external reference
is needed.


Which was what I said before moron Gene E Bloch stuck his oar in and
contradicted.
I will contradict you again, since you are ... wrong.
You will (well, *you* probably won't - or can't) note that *all* of
the things you want to call "absolute", such as dBm, dBu, and so on
(such as mentioned by Richard Crowley), are defined with respect to
a reference value. In short, and for one example, dBm gives the
*ratio* of the measured quantity to 1 milliwatt.
I would recommend to anyone who is not too IQ impaired to look at
http://en.wikipedia.org/wiki/Decibel
Naturally, I absolve you of any requirement to look there. You may
if you wish, of course, although if you do, you mght have to accept
the risk of learning something. Somehow I'm not too worried for you
:-)


One Watt ( or 1mW, or 1uW) is an absolute. A multiple of an absolute
is also an absolute, i.e., 5 times 1W, or 5W is an absolute power
level of 5W. If one chooses to express 5 times 1W as 7dBW, then it is
still an absolute.

0dBW = 1 times 1W = 1W = An absolute power level of 1W!
7dBW = 5 times 1W = 5W = An absolute power level of 5W!

Hey guys,

I'm not even sure who's right and who's wrong anymore in this, but
one thing is for certain: there are times when decibels are used
for relative comparisons without any specific power level in mind.

For example, it is commonly known that 3 dB is twice the power,
and -3 dB is half power.

In audio it is commonly accepted that it takes about 10 dB for a
sound to be perceived as twice as loud (or half as loud).

But there are certain units that ARE absolute power levels, which
I think one or both of you have already mentioned. I think the
most common is dBm, which is a dB relative to 1 milliwatt. This
is used all the time in RF measurements. There are others, as
dBW, e.g.

Of course, *I* am *absolutely* right :-)

OK, I'll get serious.

When you say "it is commonly known that 3 dB is twice the power", you
are implying something that you left unmentioned, namely *what* it is
twice the power of. The ratio in this case is to the unmentioned, but
implied, original signal.

You yourself have answered your own question when you say "there are
certain units that ARE absolute power levels ... I think the
most common is dBm, which is a dB relative to 1 milliwatt". The key
word is ... RELATIVE.

It is meaningless to say "the signal is at 12 dB", unless, of course,
the context is clear. In isolation, as I quote it in this paragraph,
there is no context. In your lab, where everybody knows that they are
working with, let's say, dBm, you of course wouldn't need to be
specific (until you publish!).

For fun, I just looked at a couple of short-wave radio S-meters. Both
have a few divisions marked from 1 to 9; these are labeled as S-units.
Both have a couple more divisions, marked +20 and +40, then the legend
dB. In this case, the dB are taken with reference to S-9 (which is an
absolute unit; I have no idea what its actual value is, though, except
that only the values from 1 to 9 are defined).

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

On 9/25/2006, Wes Newell posted this:
I don't care what you guys argue about as long as you stop crossposting
the damn messages. No need to reply. I removed the group I use.

That's OK with us too - we freely give you permission to ignore our
messages.

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

Gene E. Bloch writes:
[...]

Gene,

A measure in decibels is always a measure of a power ratio. I thought
everyone agreed to this from the git-go.

However..., someone SEEMED to be implying that anything in ANY kind
of dB units is always an absolute power level. That is not correct.

Yes, if one power is 3 dB higher, that's relative to something. Yet it
still doesn't have an absolute power level, because the power of the
"something" isn't necessarily known. All that is known is the ratio.

It's like fat-so Jimmy Clanton in 5th grade saying, "I can drink a
[schoolroom] carton of milk in half the time you can." That doesn't
specify a time.

--Former 5-second carton-of-milk champion

--
% Randy Yates % "Bird, on the wing,
%% Fuquay-Varina, NC % goes floating by
%%% 919-577-9882 % but there's a teardrop in his eye..."
%%%% % 'One Summer Dream', *Face The Music*, ELO
http://home.earthlink.net/~yatescr

On Mon, 25 Sep 2006 11:31:14 -0700, Gene E Bloch
wrote:

Gene E Bloch wrote:
I repate, in engineering, a dB figure is alwasys given with a
reference.

No it isn't. It depends if you are specifying an absolute level or a
relative one.

If you believe that, you should read this:

http://www.m-w.com/dictionary/decibel

I do believe it. That link didn't tell me anything I don't already
know.
What exactly is your point? You don't really seem to know what you're
talking about do you?

Decibels are used both as a measurement of ratio
(change) AND as a measurement of absolute level.

In the case of a ratio (change), no external reference
is needed.

Which was what I said before moron Gene E Bloch stuck his oar in and
contradicted.

I will contradict you again, since you are ... wrong.

You really are a "****ing this as pig **** American" aren't you?

You will (well, *you* probably won't - or can't) note that *all* of the
things you want to call "absolute", such as dBm, dBu, and so on (such
as mentioned by Richard Crowley), are defined with respect to a
reference value. In short, and for one example, dBm gives the *ratio*
of the measured quantity to 1 milliwatt.

I know. Now read what I wrote and understand what the word "relative"
means.
Relative measurements relate two similar quantities - the result is
dimensionless i.e. it is just a number, it has no units. Therefore it
is unnecessary and impossible to quote a reference level.

JXStern wrote:
....
When I shop the HD products, the store displays tend to have a lot of
artifacts. At least on the Best Buy bargain aisles. I haven't spent
time recently in the stand-alone HT stores, because the prices seem
about 10x higher, and I'm not that excited about it.

Nor should you be. But there are a number of sources for the
artifacts.
It may be that the original digitization was done at a low bit rate.
It may be that the transmission was done at a low bit rate.
It may be that you are seeing an SD broadcast.
The TV may not be configured well.
The TV may not be that good.

Somethings to consider:
Do all the sets in the store, including the "better" brands look as
bad? This
would tend to implicate the source or distribution.
How close are you standing to the set? One of the beauties of HD on a
big set is that if you stand close to the set, you can really see all
the
imperfections that were never visible on an analogue set, particularly
at
a greater distance.
Do *all* the sets show the same problems? If so, then the distribution
or
source material may be at fault.
Do the premier brands (Sony LCD, Panasonic Plasma, Pioneer Plasma,
Sharp
LCD) show the same problems? Remember, just be cause a set has an
HD resolution doesn't mean it's a good television. Cheap brands are
often
bad at showing motion and scaling non-native resolutions. The "big
guys"
are often quite a bit better at these things.
Try changing the TV settings. Even simple things can improve the
picture.
Change the color from Vivid to Normal or Cinema. Turn sharpening way
down. Turn down the brightness and contrast. Turn off any fancy,
gimmicy picture enhancements.

If you have friends with HDTVs, see how their sets look with different
sources. (Although there is no garauntee they have set up their sets
any
better than the big box stores have.) Also, remember that cable HD is
often compressed quite a bit more than OTA, and sattelite is often
compressed more than cable. More compression can mean poorer
picture quality.

Go look, even if you don't buy, at the sets in a higher end store, just
for comparison.


If I have an HD DVR, does it lose quality?

No. HD DVR should simply record the incoming digital information
and replay it. At least my Sony HDD250 looks just as good recorded
as live. }

....

Dan (Woj...)

"Paul Ratcliffe" wrote:

Relative measurements relate two similar quantities - the result is
dimensionless i.e. it is just a number, it has no units. Therefore it
is unnecessary and impossible to quote a reference level.

So I take it this means that when an amp is 3 dB down at some frequency,
it is "unnecessary and impossible" to answer the question "3 dB down
compared to what?"

Bert

On 26 Sep 2006 07:33:15 -0700, "dmaster"
wrote:

JXStern wrote:
...
When I shop the HD products, the store displays tend to have a lot of
artifacts. At least on the Best Buy bargain aisles. I haven't spent
time recently in the stand-alone HT stores, because the prices seem
about 10x higher, and I'm not that excited about it.

Nor should you be. But there are a number of sources for the
artifacts.
It may be that the original digitization was done at a low bit rate.

Maybe.

It may be that the transmission was done at a low bit rate.

Maybe.

It may be that you are seeing an SD broadcast.

No.

The TV may not be configured well.

Some.

The TV may not be that good.

Some.

Somethings to consider:
Do all the sets in the store, including the "better" brands look as
bad?

Generally yes, though the good ones still look better than the bad
ones.

This
would tend to implicate the source or distribution.

How close are you standing to the set? One of the beauties of HD on a
big set is that if you stand close to the set, you can really see all
the imperfections that were never visible on an analogue set,
particularly at a greater distance.

This is certainly a part of the problem, but nonetheless, if I stick
my nose up to the tube of an old SD set, the kind of inaccuracies that
analog systems display are less obvious. I guess that's the downside
of digital "clarity".

Seems to me even newer SD tubes, use more distinct pixels than I see
on older SD sets. Up close, the picture is just not as good.

Which leads to a question - are smaller LCD sets built with finer gaps
between pixels??? Two different places I'm looking to put new HD
sets, are rather narrow spaces. Larger sizes may be contraindicated.


Try changing the TV settings. Even simple things can improve the
picture.

These appear to me to be compression artifacts. I'm not aware of any
user controls on such things. Are there?

Go look, even if you don't buy, at the sets in a higher end store, just
for comparison.

I have seen great HD, and I have no doubt that it can be set up if you
control all the way back to the source, but my concern is with what is
coming in via OTA, cable, etc. I'm concerned a lot of them are
introduced way upstream for commercial materials.

Again, to some extent, it doesn't matter, at the end of the day you
pays your money, takes the box home, and lives with the results. I
want to make sure I understand what the options are so I can choose
well, and heck, I'm used to understanding tech stuff, so the
difficulty of finding answers to even easy questions on this stuff is
a bit frustrating.

If I have an HD DVR, does it lose quality?

No. HD DVR should simply record the incoming digital information
and replay it. At least my Sony HDD250 looks just as good recorded
as live. }

Thanks.

J.

Albert Manfredi wrote:
"Paul Ratcliffe" wrote:

Relative measurements relate two similar quantities - the result
is
dimensionless i.e. it is just a number, it has no units. Therefore
it
is unnecessary and impossible to quote a reference level.

So I take it this means that when an amp is 3 dB down at some
frequency,
it is "unnecessary and impossible" to answer the question "3 dB down

compared to what?"

Bert

In Bert's example, the reference 'level' is generally taken as 1KHz.
This level is temporarily defined as 0 and then the sweep response is
relative to that initial level. Often it is defined at 1 watt out but
it is not etched in stone.

Fluke makes this VERY easy to measure with the 'relative' button on the
meter that defines the present value as '0'

GG