Some Technical Questions

squicken

squicken

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Since there are alot of people who seem well schooled in the way of HDTV technology, I have a few questions.
I live in the 174th largest DMA, so I feel very lucky to have my NBC affiliate in 1080i, and my FOX affiliate already broadcasting in 720p (they are currently upconverting the 480p stuff they get from FOX national). My ABC and CBS are owned by the same company, and share facilities. How that is even legal I have no idea, but my FOX and UPN are both owned by the same parent. I have been trying to talk with someone at my local ABC or CBS for 2 weeks, but have not received replies to my emails or phone calls. My first question concerns power level. According to a tech sheet I read, NBC here is broadcasting its analog at 130kw. The digital NBC is at 13kw. Is that consistent? Does digital need less power than analog? Are they measured differently? Both stations are VHF, if that matters.

I can receive my local CBS digital, but not my ABC digital. My installer said the ABC digital is VERY low power. Does that mean ABC has a bad tower? Is it just a matter of flipping a switch to give it more juice?

My NBC affiliate multicasts it digital signal. I think the HDTV looks great, but have read others post that multicasing hurts PQ. How does it hurt it? Also, my NBC is not in 5.1. Is that NBC national policy, or just my local?

I also have a last question on something my NBC station engineer told me. He was just awesome, and answered every question I had and even offered opinions and information I had no ideas about. He said NBC choose 1080i b/c it was superior to 720p. He said 720p refreshes the entire screen 60 times a second, whereas 1080i does it 30 times a second. He said that the refresh rate didn't matter b/c NBC filmed its shows, and film only has 24 pictures per second. I'm not trying to relive this old 1080/720 argument. But is that accurate?

I have seen many people on this forum who seem to have a great deal of knowledge on these subjects, and appreciate everyone's help.
 
C

cameron119

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Apr 18, 2004
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NBC may keep an archive film, but the shows are electronically recorded with HD or SD equipment for broadcast. Multicasting reduces quality by reducing available bandwidth on the digital channel. Digital sources usually do require less output power than an analog source. I'm not sure about 130,000 W vs. 13,000 W though.

1080i is nice, 720p is nice. In passing, most folks won't know the difference. They just know it's a helluva lot better than 480i or 480p.

Technically, 1080i allows you to perceive full 1080 resolution. Some people are more sensitive to interlacing, especially if you scrutinize the picture and catch the interlacing in action. That can hurt your experience, since after that you will notice the interlacing more commonly. 1080i makes up for this in spades with sharpness and resolution.

720p is progressive scan, so what you perceive is actually there. Fast motion scenes will pass smoothly, allowing you to keep a clear eye on the action as the camera moves. Some folks don't notice 1080i's interlacing, many times it isn't even noticeable.

Fact is, these standards are both excellent. They really shine when viewed natively. Most people won't even be able to do that, so for them the argument is moot. Watch the highest resolution your set natively supports and enjoy it already. If your set happens to support both 1080i and 720p NATIVELY, play with the settings and see what you like.
 
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Ken F

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Mar 8, 2004
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My NBC affiliate multicasts it digital signal. I think the HDTV looks great, but have read others post that multicasing hurts PQ. How does it hurt it?
Multicasting reduces the bandwidth available for the HD channel. For some content, reducing the bandwidth (bit rate) to accomodate a second channel may not make a noticeable difference. On other content (especially live sports), it can make a significant difference. When a HD channel is provided indequate bandwidth, you'll see a) a softer picture with less detail, b) lots of compression artifacts -- most commonly observed on scenes with movement, or b) some combination of the two.



Also, my NBC is not in 5.1. Is that NBC national policy, or just my local?
NBC does not currently offer 5.1. ABC, CBS, and FOX offer 5.1, although not necessarily on all programming.


I can receive my local CBS digital, but not my ABC digital. My installer said the ABC digital is VERY low power. Does that mean ABC has a bad tower? Is it just a matter of flipping a switch to give it more juice?
They may be waiting for construction to commence (or finish) on a new tramsnitter for their digital signals. If they are low power, this probably because the transmitter they are using is temporary.
 
squicken

squicken

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Thanks for the info guys. It would be that much better if they returned phone calls.
 

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