[Solved] CRT TVs

MrChips

Joined Oct 2, 2009
30,712
Do the math.
There are 525 cycles at 15.734kHz.
This takes 525 / 15734 = 0.033367s = 33.367ms
This is the time it takes to generate one frame.
33.367 / 2= 16.685ms (with rounding errors) is the time to generate one field and this is the Vertical scan interval (close to 60Hz),

The fact that 525 is an odd number means that whereas the even field is in sync with the Vertical Scan, the odd field begins halfway through the Horizontal Scan.

Also, remember that you cannot stop the oscillators. You get 525 cycles at 15.734kHz but you cannot see 525 lines. Only 480 lines are visible.
 

MisterBill2

Joined Jan 23, 2018
18,176
And all of this is about NTSC format video, no longer used for broadcast TV in the US. Now we have digital TV, much easier to encrypt more effectively, and in addition it made every TV with NTSC obsolete.
The claim was that it improved the resolution, but that is only a secondary benefit. Unfortunately most of the programming would still be just as good with the old CGA resolution. And all of the reruns are still NTSC, converted to digital, but not any better video quality. So the benefit to the general population is questionable. The benefit to the hardware produces is obvious.
 

crutschow

Joined Mar 14, 2008
34,283
I don't k
And all of the reruns are still NTSC, converted to digital, but not any better video quality.
Many of the reruns were recorded directly to film so have HD quality.
I've seen a number of old reruns that have very good resolution, such as the original Star Trek.
To see what the poor resolution of NTSC video recordings look like, view some of the old NFL games.
 

ronsimpson

Joined Oct 7, 2019
2,988
Not on topic but we are just circling "TV land" so here goes.
Sales manager at the store is pushing people to pay for 4k TV. (more commission)
The picture is compressed. Probably not recorded in 4k. Most of my complaints is the compression.
My TV shows that about 1 in 4 stations are in "1080 I" and the rest are in "480 I".
I think a couple of million pixels does nothing to improve the resolution and certainly can not improve the compression.
Your thoughts?
 

DickCappels

Joined Aug 21, 2008
10,152
A perfectly adjusted NTSC camera connected directly to a carefully set up NTSC monitor in a dimly lit room could make a breathtaking image that doubling the number of active lines could not improve on.
 

crutschow

Joined Mar 14, 2008
34,283
Most of my complaints is the compression.
All HD signals are "compressed".
Otherwise each station would require a 20MHz RF signal bandwidth or more.
What's your complaint?
My TV shows that about 1 in 4 stations are in "1080 I" and the rest are in "480 I".
Digital transmissions are 1080i or 720p.
If you are getting 480i, it's from the twilight zone. :rolleyes:
 

Thread Starter

biferi

Joined Apr 14, 2017
390
Ok I think I have the way the Scan Lines work?

When you Turn on the CRT TV the Electron Gun would Start to Draw the Odd Lines First.
It would Start at the Top Left of the CRT TV and End in the Bottom Center facing the Right.

Then the Electron Gun would Start the Even Lines at the Top Left but Right under where the First Scan Line was.
And it would End all the way at the Bottom Far Right.

Just Tell me if I have this?
 

ronsimpson

Joined Oct 7, 2019
2,988
All HD signals are "compressed".
What's your complaint?
I spent most of a life time playing with video. I was designing video products for Sony when they were compressing video for video phones. I watch that grow up to broadcast video. We spent pieces for several years comparing different types of video compression. That has destroyed my enjoyment of HD TV. Sports or (movies with chase scenes never intended for TV) are hard for me to watch. Yesterday I saw a chase scene in a corn filed. The compressor totally lost it. I see rectangles all over the picture, artifacts of compression. Colors and shading shifting as people move. The scientific and medical monitors and cameras would never put up with any of this. The military targeting monitors would be worthless. When I walk into a TV store I can see what sets are not set up correctly.

I think digital TV is wonderful. Just, I know how it works and when it is not doing a good job.
 

Dodgydave

Joined Jun 22, 2012
11,285
Ok I think I have the way the Scan Lines work?

When you Turn on the CRT TV the Electron Gun would Start to Draw the Odd Lines First.
It would Start at the Top Left of the CRT TV and End in the Bottom Center facing the Right.

Then the Electron Gun would Start the Even Lines at the Top Left but Right under where the First Scan Line was.
And it would End all the way at the Bottom Far Right.

Just Tell me if I have this?
Yes it does,

But it only scans in order when it receives the sync pulse from the signal ,

Without the sync pulses the tv will just scan at random .
 

MisterBill2

Joined Jan 23, 2018
18,176
It has neem a very long time since I saw anything on TV that would be any better in "echtachrome" quality, which was the very best consumer quality film that was available 15 years ago. most TV programs would be no worse in CGA quality video.
Digital TV is OK, but I still think that the main goal was to create a market for new technology.
 

Thread Starter

biferi

Joined Apr 14, 2017
390
Ok thanks to everybody for the help.
And thanks to the Internet I think I have it down?

When you Turned On the CRT TV the Electron Gun would Start to Draw the Odd Lines fro, Top Center and Down the Screen.
But it would End on the Far Bottom Right.

Then the Electron Gun would Start to Draw the Even Line at the Top Far Left and go Down the Screem.
But End at the Bottom Center.

I found an Image is this Right?
 

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Thread Starter

biferi

Joined Apr 14, 2017
390
No as Far as LCD TVs go does each Pixel Light Up Right next to one another and move Left to Right like the Electron Beam did in the CRT TVs?

Or do all of the LCDs Light Up at the same Time and the only ones that Change are the ones that are moving on Screen like a Car?
 
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