Do you really like the way HDTV looks?
 

Matthew L. Martin wrote:

Absolutely false. Interlace scan was used to reduce the bandwidth
required for transmission..

Would you care to show everyone the math for that? You are still
sending the same amount of data in the same time frame per frame.

Something is missing from the statement after the word transmission.
It should have read:

Interlace scan was used to reduce the bandwidth required for
transmission of a maximum resolution image in a fixed bandwidth
analog channel.

The original patent for this technique (U.S. Pat. No 2,152,234) puts it
this way:

--- 8 ---

From the foregoing it will be seen that by my improved method and system
it is possible to substantially increase the number of picture lines
without increasing the required frequency channel. Furthermore, by using
my improved method of scanning, the optical effect, referred to as
"flicker", is eliminated or reduced to a negligible degree.

--- 8 ---

--
znark

Do you really like the way HDTV looks?
 

"Thumper" wrote in message
...
On 16 Sep 2006 21:31:31 -0700, "
wrote:


Martin Heffels wrote:
On Sat, 16 Sep 2006 21:32:14 GMT, Dave Oldridge
wrote:

Of course it may be masked by the
original blur, and that's why interlaced scan was used for NTSC in the
first place. It's not really that noticeable except in certain
conditions.

Interlaced scan was used because in the beginning it was not possible
for
the phosphors on the tube to "keep" the picture all the time for the
whole
500 or so, lines.

-m-
--

Absolutely false. Interlace scan was used to reduce the bandwidth
required for transmission..

Then why interlaced computer monitors?
Thumper

Same difference... back in the old days, it took quite a bit of the
processor just to get the bits to the screen... half the bits per second
meant time left over to actually run a spreadsheet calculation.

Do you really like the way HDTV looks?
 

"Michael A. Terrell" wrote in
:

Dave Oldridge wrote:

Still, a lot is shot on 35mm. My Buffy DVD's have a commentary
somewhere. They started with 16mm and then, after one season, when
they actually had some money, they switched to 35mm. But even 16mm
is WAY better than most NTSC broadcast TV resolution.


16 mm was the medium of choice back in the early '70s when I
started
working as a broadcast engineer. That's how non network programming
was fed to stations without 2" R-R or the new U-matic machines. 16 mm
blew away the first generation of U-matic for picture quality on a
good film chain projector and camera, while a good 2" tape machine
could cost more than everything else in the control room of a small
station. By the time I left Broadcasting, the 1" R-R machines had
taken over. U-matic was a lot better, but you could still tell the
difference on a studio monitor. The biggest problem in video quality
with the standard NTSC video was the cheap TV sets, and lower grade
CRTs. It was amazing when you brought a fairly decent TV set into the
station, and compared it to a $3,000 inline monitor, and even more so
against the master monitor, which was a $7,000 traditional tri-gun
CRT. Even fed off air by the Tektronix Demodulator, that monitor
still blew everything else away.

Yes, I used to use a 19-inch electrohome studio monitor for my home TV
for some time, just using the tuner in my VCR and later a Sat receiver to
provide the video.

That monitor easily handled 640x480 computer generated graphics, too.

I still laugh when I remember the cable guy coming to my door by mistake
and asking where I wanted the cable hookup. I pointed to the 48-inch Ku
dish on the porch and the crystal-clear picture from NBC on my monitor
and said, "Does it LOOK like I need cable?"


--
Dave Oldridge+
ICQ 1800667

Do you really like the way HDTV looks?
 

Martin Heffels t wrote
in :

On Sat, 16 Sep 2006 21:25:40 GMT, Dave Oldridge
wrote:

Uh, they are still a ratio. And I do believe that clarity perception
is of a similar logarithmic nature to sound, so the analogy is apt.

Nah, optical is in lines per inch, not dB. As far as I know that would
be linear and not logarithmic (exposure is logarithmic though).

Its perception is by eyeball and brain. These ARE logarithmic.


--
Dave Oldridge+
ICQ 1800667

Do you really like the way HDTV looks?
 

Martin Heffels t wrote
in :

On Sat, 16 Sep 2006 21:32:14 GMT, Dave Oldridge
wrote:

Of course it may be masked by the
original blur, and that's why interlaced scan was used for NTSC in the
first place. It's not really that noticeable except in certain
conditions.

Interlaced scan was used because in the beginning it was not possible
for the phosphors on the tube to "keep" the picture all the time for
the whole 500 or so, lines.

Yes, but it's really only feasible because most motion is already blurred
from the source.


--
Dave Oldridge+
ICQ 1800667

Do you really like the way HDTV looks?
 

Paul Keinanen wrote in
:

On Sat, 16 Sep 2006 21:25:40 GMT, Dave Oldridge
wrote:

Martin Heffels t
wrote in :

On Fri, 15 Sep 2006 19:22:02 GMT, Dave Oldridge
wrote:

3db is not a really LARGE difference in clarity.

Decibels have nothing to do with the clarity of your picture. You
(usually) use them to tell a difference in power, voltage or
soundlevel.

Uh, they are still a ratio. And I do believe that clarity perception
is of a similar logarithmic nature to sound, so the analogy is apt.

While it would make sense to look at the noise floor of an analog
baseband video signal with a spectrum analyzer and from determine the
signal to noise ratio and express it in decibels, how do you make any
objective measurement on digital signals with variable quantisation

It's not objective. It's subjective. And human perception tends to the
logarithmic, hence the use of db.


--
Dave Oldridge+
ICQ 1800667

Do you really like the way HDTV looks?
 

On Sun, 17 Sep 2006 21:13:09 +0300, "Jukka Aho"
wrote:

Paul Keinanen wrote:

The interlaced scanning was patented as a bandwidth reduction method
in 1930, i.e. in the mechanical scanning era. The early TV experiments
were around 12 frames/s with the signal fitting into one audio channel
bandwidth. With interlace the update rate could be increased to 24
fields/s and the signal would still fit into the audio channel.
Instead of one spiral of holes on the Nipkov disk, one spiral of holes
occupied half of the disk, while an other, slightly offset spiral
occupied the other half.

Wikipedia attributes this invention to Randall C. Ballard, an RCA
engineer. Apparently it is the US Patent Number 2,152,234 - originally
filed July 19, 1932 and granted March 28, 1939:

http://patimg1.uspto.gov/.piw?Docid=02152234

That may well be the first U.S. patent for interlace, but the name
Fritz Schröter working for Telefunken pops up quite often.

The only exact reference I could find was (Fritz Schröter: "Verfahren
zur Abtastung von Fernsehbildern", DRP-Patent Nr. 574085, Anm.
27.09.1930) which appears on the page www.ahok.de/dt/palplus.html as a
historical peculiarity. Unfortunately those pre-war German patent
archives do not appear to be online anywhere, so I can not check the
validity.

Paul

Do you really like the way HDTV looks?
 

Martin Heffels wrote:

Interlaced scan was used because in the beginning it was not possible
for the phosphors on the tube to "keep" the picture all the time for
the whole 500 or so, lines.

Curiously, the text of Randall C. Ballard's patent regarding interlace
tells us that:

--- 8 ---

My invention relates to improvements in television systems and, more
particularly, to an iomproved method of scanning.

In the art of television, wherein a moving picture film with a sound
track thereon is the object televised, satisfactory results have been
obtained by using a scanning disc at the transmitting station for
transmitting the picture and a cathode ray tube at the receiving station
for reproducing the picture. An important advantage of the cathode ray
tube for receiving purposes resides in the feature of retentivity of
fluorescence of the fluorescent screen with which the tube is provided,
which screen is scanned by the cathode ray. In this connection, it has
been determined that, for the purpose of making use of this fuorescence
to the best advantage, the received picture frequency should not be
materially greater than sixteen pictures per second. However, when using
standard sound-film, it is necessary, at the transmitter, to run the
film at the usual normal rate of 24 frames a second to reproduce the
sound faithfully.

Various methods and constructions have been proposed for the purpose of
permitting simultaneous occurrence of the two conditions of operation
referred to, that is, scanning the film at a rate not greater than
sixteen pictures per second, and running the film at the usual rate of
24 frames per second.

One of the methods proposed heretofore has been to run the film at the
normal rate of 24 frames a second, but to scan only every second, third,
or fourth picture of the film. Another method proposed has been to make
a slow-speed film from the standard film, in which case the correct
reproduction of the sound was obtained with the film running at a speed
not greater than sixteen picutres per second, and every picture was
scanned. Thes methods, as well as the various other methods proposed
heretofore, are costly and/or cumbersome.

With the foregoing in mind, it is one of the objects of my invention to
provide an improved television system, for the transmission of standard
sound-film, wherein the film is run at the normal rate and is scanned in
such a manner as to obtain full advantage of the fuorescent effect in a
cathode ray tube at the receiving station.

Another object of my invention is to provide an improved television
system for the transmission of sound film, wherein the frequency channel
required for television is reduced without changing from the standard
rate of 24 pictures a second at which the film is run.

Another object of my invention is to provide an improved method of
operation whereby the number of picture lines can be substantially
increased without necessitating an increase in the required frequency
channel.

Another object of my invention is to provide an improved method whereby
the optical effect, referred to as "flicker", is eliminated or reduced
to a negligible degree.

Other objects and advantages will hereinafter appear.

--- 8 ---

(U.S. Patent 2,152,234: http://patft.uspto.gov/netacgi/np
h-Parser?patentnumber=2,152,234)

What does he mean by "it has been determined that, for the purpose of
making use of this fuorescence to the best advantage, the received
picture frequency should not be materially greater than sixteen pictures
per second", exactly?

Note that the patent seems to discuss a narrowband 24-fields-per-second,
(interlaced) 80-line television system with 77 active lines.

--
znark

Do you really like the way HDTV looks?
 

A bel (or decibel=1/10 bel) is classicly a measure of sound ratio. Audio SPL
levels are the relationship between what the human ear can actually detect and
the power required to deliver that difference. For example: a +3dbspl level
(generally considered the minimum differential that the human ear can perceive)
requires twice the RMS audio power. (work it out in powers of 2 beyond that)
Here is a dictionary definition of bel:
n 1: a logarithmic unit of sound intensity equal to 10 decibels [syn: {B}] 2:
Babylonian god of the earth; one of the supreme triad including Anu and Ea;
earlier identified with En-lil
Since I don't think we are talking about the Babylonian trinity here, as a
concert sound engineer, I would opt for the first definition.
HOWEVER...the point of clarity perception measured using a logarithmic function
seems reasonable. Let's just figure out what it is exactly, and give it a
different name.
Sound S/N ratio has always been expressed as decibels. I'm comfortable with a
video S/N being also proffered as decibels

--
All the Best
Richard Harison

"Dave Oldridge" wrote in message
9...
Martin Heffels t wrote
in :

On Fri, 15 Sep 2006 19:22:02 GMT, Dave Oldridge
wrote:

3db is not a really LARGE difference in clarity.

Decibels have nothing to do with the clarity of your picture. You
(usually) use them to tell a difference in power, voltage or
soundlevel.

Uh, they are still a ratio. And I do believe that clarity perception is of
a similar logarithmic nature to sound, so the analogy is apt.


--
Dave Oldridge+
ICQ 1800667



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Do you really like the way HDTV looks?
 

A bel (or decibel=1/10 bel) is classically a measure of sound ratio. Audio SPL
levels are the relationship between what the human ear can actually detect and
the power required to deliver that difference. For example: a +3dbspl level
(generally considered the minimum differential that the human ear can perceive)
requires twice the RMS audio power. (work it out in powers of 2 beyond that)
Here is a dictionary definition of bel:
1: noun: a logarithmic unit of sound intensity equal to 10 decibels
2 Babylonian god of the earth; one of the supreme triad including Anu and Ea;

Since I don't think we are talking about the Babylonian trinity here, as a
concert sound engineer, I would opt for the first definition.
HOWEVER...the point of clarity perception measured using a logarithmic function
seems reasonable. Let's just figure out what it is exactly, and give it a
different name and then figure out its significance!
Sound S/N ratio has always been expressed as decibels. I'm comfortable with a
video S/N being also proffered as decibels.

--
All the Best
Richard Harison

"Dave Oldridge" wrote in message
9...
Martin Heffels t wrote
in :

On Fri, 15 Sep 2006 19:22:02 GMT, Dave Oldridge
wrote:

3db is not a really LARGE difference in clarity.

Decibels have nothing to do with the clarity of your picture. You
(usually) use them to tell a difference in power, voltage or
soundlevel.

Uh, they are still a ratio. And I do believe that clarity perception is of
a similar logarithmic nature to sound, so the analogy is apt.


--
Dave Oldridge+
ICQ 1800667





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