help an uneducated...........

bnewt · 01-17-2005, 03:17 PM

I know that I have read this somewhere, but can't find it now. Why do digital signals look diferent than analog signals? Comparing my ota locals in analog & digital, the digitals look like they have horizontal lines running across the screen, while the analog doesn't.

martin1 · 01-17-2005, 03:44 PM

Quote:

Originally Posted by bnewt

I know that I have read this somewhere, but can't find it now. Why do digital signals look diferent than analog signals? Comparing my ota locals in analog & digital, the digitals look like they have horizontal lines running across the screen, while the analog doesn't.

Something is not right. Are you watching on a HD tv.
All tv signal has horizontal line. SD has 480 line.
If you are watching hd tv ota it should have 720 line or 1080 lines depending what your tv will accept. So hd had more lines hence should be more detail. It possible that you are receiving a digital signal but before it gets to your tv you are converting it back to sdtv
via your set top box.

bnewt · 01-18-2005, 10:05 AM

Yes, that is correct. My tv is an older analog tv. Both my satellite receiver & now my ota stb, I assume convert the signal to 480i. At least I know that is what I set the stb.
Are you saying that with a hd set, these lines will not be present on the screen? I thought that was the description of the "screen door" comlaints with hd pictures.

**rbinck** · 01-18-2005, 10:26 AM

It depends on which type of HDTV you get. CRT based HDTVs do not have any perceptivable scan lines because most of them use 1080i for display. Tha's more than double SD lines.

On LCD, DLP and to some extent LCOS TVs you will have the screen door effect, both front projection and rear projection. The bigger the screen, the more it shows up. On plasma panels you have the individual pixels that some people can see up close. On direct view CRTs you have the individual phospher clusters that you can see close up.

You didn't tell us what TV you have, but some of the early big screen CRT based TVs had line doublers for the tuner video, but not for the composite video. Who knows why? These TVs would have 800 line video while watching the internal tuner, but not on other inputs.

Bottom line is on a HDTV you will not notice scan lines like you get on a SD TV, but if you get one too big for your viewing distance, you may see the screen door on certian types.

If you go shopping for a HDTV, I suggest you try to match your viewing enviroment as close as possible and insist on seeing the type of programming you normally watch. Remember, Finding Nemo is used because it will help to sell TVs.

01-17-2005, 03:17 PM	#1
bnewt High Definition is the definition of life. Join Date: Nov 2004 Posts: 36	help an uneducated........... I know that I have read this somewhere, but can't find it now. Why do digital signals look diferent than analog signals? Comparing my ota locals in analog & digital, the digitals look like they have horizontal lines running across the screen, while the analog doesn't.

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01-18-2005, 10:05 AM	#3
bnewt High Definition is the definition of life. Join Date: Nov 2004 Posts: 36	Yes, that is correct. My tv is an older analog tv. Both my satellite receiver & now my ota stb, I assume convert the signal to 480i. At least I know that is what I set the stb. Are you saying that with a hd set, these lines will not be present on the screen? I thought that was the description of the "screen door" comlaints with hd pictures.

01-18-2005, 10:26 AM	#4
rbinck Administrator Join Date: Apr 2004 Location: Katy, Texas Posts: 15,637	It depends on which type of HDTV you get. CRT based HDTVs do not have any perceptivable scan lines because most of them use 1080i for display. Tha's more than double SD lines. On LCD, DLP and to some extent LCOS TVs you will have the screen door effect, both front projection and rear projection. The bigger the screen, the more it shows up. On plasma panels you have the individual pixels that some people can see up close. On direct view CRTs you have the individual phospher clusters that you can see close up. You didn't tell us what TV you have, but some of the early big screen CRT based TVs had line doublers for the tuner video, but not for the composite video. Who knows why? These TVs would have 800 line video while watching the internal tuner, but not on other inputs. Bottom line is on a HDTV you will not notice scan lines like you get on a SD TV, but if you get one too big for your viewing distance, you may see the screen door on certian types. If you go shopping for a HDTV, I suggest you try to match your viewing enviroment as close as possible and insist on seeing the type of programming you normally watch. Remember, Finding Nemo is used because it will help to sell TVs.