Do you really like the way HDTV looks?

On Tue, 12 Sep 2006 15:05:24 GMT, "Albert Manfredi"
wrote:

But not all DTV is alike. Some Standard Def digital programs, for
example, are sharp and clear. Others look just about as grainy and fuzzy
as analog TV. The nice thing about HDTV is that *finally* you can see TV
pictures that are as sharp and clear as the best images on a PC monitor.

Absolutely. I just watched a baseball game on Fox HD and it's not
nearly as good as the quality of a baseball game on ESPNHD. Even
within a single program you can see quality variations depending on
the source of the footage.

On 9/23/2006, Paul Ratcliffe posted this:
On Mon, 18 Sep 2006 23:16:19 GMT, Michael A. Terrell
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

[...]

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

On Sat, 23 Sep 2006 15:29:17 -0700, 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?

"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. For example, saying that a speaker is 3dB
down at 100Hz. Its gonna roll off that way no matter
how loud or soft it is playing.

But in the case of a level, dB is meaningless without
the reference such as "dBu" or "dBm", or "dBv" etc.

Note that this applies to both elecrical measurements
and acoustical measurements. For example, microphone
sensitivity is commonly cited in dB relative to 1V/Pa,
etc.

Don't forget dbSPL (annotated as dba ("A" weighted) or dbc ("C" weighted) as
used in measurements of "absolute" sound volume

--
All the Best
Richard Harison
"Richard Crowley" wrote in message
...
"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. For example, saying that a speaker is 3dB
down at 100Hz. Its gonna roll off that way no matter
how loud or soft it is playing.

But in the case of a level, dB is meaningless without
the reference such as "dBu" or "dBm", or "dBv" etc.

Note that this applies to both elecrical measurements
and acoustical measurements. For example, microphone
sensitivity is commonly cited in dB relative to 1V/Pa,
etc.



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"Richard Crowley" wrote:

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

Decibels are always a ratio. dB = 10*logbase10(P2/P1), so the power
ratio must exist.

(Or it can be expressed in other ways, such as a ratio of voltages,
which then becomes 10*logbase10(V2^2/V1^2), or 20*logbase10(V2/V1).
Because power is a function of the square of the voltage.)

In the case of a ratio (change), no external reference
is needed. For example, saying that a speaker is 3dB
down at 100Hz. Its gonna roll off that way no matter
how loud or soft it is playing.

But when you say some level is 3 dB down, you are saying the output
power at the given frequency is 50 percent of the power at some optimal
frequency. So the reference is the power at whatever optimal frequency.

In the specific example, if P2/P1 is 1/2, then
dB = 10*logbase10(0.5)
= 10*(-.3010)
= -3.01 dB.

But in the case of a level, dB is meaningless without
the reference such as "dBu" or "dBm", or "dBv" etc.

Exactly. For example, dBm is referenced to 1 mW. So dB is always a ratio
with respect to some reference.

Bert

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.

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 :-)

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

On Tue, 12 Sep 2006 06:35:25 -0400, "Jim Mack"
wrote:

HiC wrote:
Went into a local Circuit City and took a good long look at their HDTV
selections. They had several including 2 1080p sets that I was told
were set up correctly and what I was seeing was as good as it gets.
Everything HD from the cams to the screen. Both the 1080p's were
running some sort of hard drive unit, not off a broadcast.

As many have said, it isn't just the set that's off. If it's coming from
a hard drive then it's likely that it's re-compressed at a bit rate around
12-15Mb/s, maybe even from an original off-air signal that was broadcast
at 18Mb/s. When you consider that the prime source used maybe 400Mb/s,
you can see why it might suffer.

If you'd seen original film transfers or studio-quality video
on a decent monitor you'd know why HD is praised. But then, if you'd
seen high-end SD in the same environment you would probably have
thought you were seeing HD, so poor is the current delivery of TV to the home.

Unfortunately, what you saw _is_ as good as it gets for most people.
Squeezing high-bitrate video down a soda straw delivery 'pipe' robs
HD of what makes it shine. "Digital" in home TV terms means
low-bitrate MPEG. Yeah, it's noise-free. It's also quality-free.

I'm still trying to figure out what I'm seeing and what they're
selling, this is all very helpful.

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.

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

I just can't see how all these data-rate and conversion issues are
going to result in realizing the capabilities of HD. I've seen full
data-rate, full resolution HD (for ten years or more) and it blows
your socks off, but now that we have these big, new screens, I'm
worried that the image delivered will be barely up to OTA NTSC, and
not as good as DVD played on my old analog set. OK, that's too
gloomy, the images overall are better, but then the artifacts take it
back on down again. Y'know what drives me crazy, the occassional NTSC
broadcast now that is obviously filmed in HD and compressed (badly)
back down to NTSC, sports events seem to be viewed through vaseline,
and even worse when they compress the picture so they can roll some
current scores (and ads) stripe along the bottom. Do they do that on
the HD broadcast, too? Yikes. Too many toys in the broadcast booth.

J.

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!