Research ALERT!

#1
We have approximately 100 minutes to research the difference in quality from our broadcasters.

Currently, the same feed for Haiti is on just about every network channel.

At this time you can compare the exact feed from each of your stations. Look for differences in picture and sound.

Those with similar signal strengths across stations should see the same quality across stations. Those with varying signal strengths could see differences in the quality of the picture. To most easily see this, watch your lowest signal for 15 minutes or so, then switch to your highest signal strength.

Let's go!
 

Trip

Moderator, Webmaster of Rabbit Ears
Staff member
#2
Signal strength should not impact picture quality unless the signal is right on the border between decoding and not decoding.

- Trip
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#3
That is what I learned recently, from the guys on the forum here. That is how the error correction circuitry works, its perfect or the picture fails.

The bit rates from channel to channel are differnent though...and that does affect quality. RabbitEars.info has information on those bit rates for channels and subchannels.
 
#4
Gentlemen,

I have what is considered by some, as very distressing news.

Digital picture isn't all or nothing.

Several years ago I began searching for the answers to the variations I'd witnessed and heard about. Shortly after beginning to install Dish satellite systems, I went to a service call. I said "Hi" and looked at the perfect black-and-white picture on his old television. I asked him "What was the problem?", to which he replied, "It's a COLOR TV!".

"Knowing" what I'd been told about digital being "All or nothing", I was already set in my mind that he would need a new television. But, integrity said to check his system and give him his money's worth for me showing up. As usual, I reached behind his receiver to check that the feed line was tight and as soon as I touched it, it fell out in my hand. "Knowing" what I knew about digital, replacing this fitting wouldn't change anything, but it needed to be fixed. I replaced the fitting and screwed the line back into the receiver. As the receiver fired up with signal, the television came back IN COLOR!

Now, perfect black-and-white picture is far from "all" and far from "nothing". I asked everyone I knew how or why that happened. I got the same response from everyone, "It shouldn't have happened."

Well, it did happen and I decided then, if no one knew the answers, then I'd find out for myself. That was in late 2005. by the grace of God, I am smarter and wiser, now.

What we've been told about digital picture might have been true at one time. What we've been told about MPEG and FEC needs revision also.

I hope that the understanding of this will be found in the article I hope to write soon, "Exploring MPEG"

Please keep an open mind...the science backs my observations.
 

IDRick

DTVUSA Member
#5
Jeff,

My apex converter box outputs signal via composite or s-video. If the s-video is not properly seated, there is a greenish cast on the video from *all* stations. Correct connections and no multipath are assumed in the "all or nothing" statement relative to digital OTA signals. IMO, the appropriate slant to your article would be "exceptions to the rule" rather than is the rule valid or not.

JMO,

Rick
 
#6
Rick,

There are many things that can affect picture quality. Green cast always points me to a bad cable or connection. Good one to remember!

Actually, I can't think of one case where anything digital is "all or nothing", so I'm not sure what you are saying. (Don't get me wrong, I am interested in what you are referring to.)

What about digital television IS "all-or-nothing"?

Did you read "Examining MPEG 2,4 and FEC?

P.S. I am aware that I'm still dragging on giving you an answer on a previous thread. I wanted to lay some groundwork before jumping in on that one.
 
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IDRick

DTVUSA Member
#7
Hi Jeff,

I was thinking of the digital cliff data that I posted in a different thread. Based on my signal quality meter and my visual appraisal, there is no difference in picture quality until I'm within a few dB's of the digital cliff. IMO, digital reception is very close to "all or nothing" or stated differently (high quality or nothing). Yes, I have experienced multipath where there are huge effects on picture quality even though there is plenty of margin (signal above losses from antenna through distribution system + receiver). IMO, that is an exception, rather than a rule.

No, I had not heard of the article "Examining Mpeg 2,4, and FEC". Is it available on line?
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#9
I did an examination of the studio feeds of singers, that night.

Tough to make out much differences. I thought I noted some color saturation and contrast differences, perhaps attributable to image processing at the local broadcasters. But Im not sure. I dont know how they handle the signals coming in like that...if they run them straight through or what.

The 720p station FOX 24 WTAT didnt seem to be any less sharp to my eye either.

I think that the ABC affiliate WCIV uses the highest bit bandwidth for the primary HD channel. They all have 1 sub channel and 1080i, except for WTAT which is 720p and no sub.

WCIV is also prone to more reception issues with pixelation. I wonder if they are connected. Its high bitrate and this.
 
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#10
All I could tell from one to the other was better sound on PBS.

I even switched to my "waterfall" (previously "cliff") signal and again, the only difference I could identify was PBS sound.

Here it needs to be stated:

You may have low signal and NOT see any picture disruption. It all depends on what portion of data is corrupted.

The important thing to remember is that IF someone has complaint of poor picture quality, they're not crazy and there are answers.

Usually, it is either signal or calibration. These two make up the largest differences witnessed in PQ variations. (Not counting those who don't have source, cables, etc. correct.)
 

FOX TV

Contributor
#11
B & w

Gentlemen,

I have what is considered by some, as very distressing news.

Digital picture isn't all or nothing.

Several years ago I began searching for the answers to the variations I'd witnessed and heard about. Shortly after beginning to install Dish satellite systems, I went to a service call. I said "Hi" and looked at the perfect black-and-white picture on his old television. I asked him "What was the problem?", to which he replied, "It's a COLOR TV!".

"Knowing" what I'd been told about digital being "All or nothing", I was already set in my mind that he would need a new television. But, integrity said to check his system and give him his money's worth for me showing up. As usual, I reached behind his receiver to check that the feed line was tight and as soon as I touched it, it fell out in my hand. "Knowing" what I knew about digital, replacing this fitting wouldn't change anything, but it needed to be fixed. I replaced the fitting and screwed the line back into the receiver. As the receiver fired up with signal, the television came back IN COLOR!

Now, perfect black-and-white picture is far from "all" and far from "nothing". I asked everyone I knew how or why that happened. I got the same response from everyone, "It shouldn't have happened."

Well, it did happen and I decided then, if no one knew the answers, then I'd find out for myself. That was in late 2005. by the grace of God, I am smarter and wiser, now.

What we've been told about digital picture might have been true at one time. What we've been told about MPEG and FEC needs revision also.

I hope that the understanding of this will be found in the article I hope to write soon, "Exploring MPEG"

Please keep an open mind...the science backs my observations.
If this connection was from the RF modulator to the TV, you may have had a bad connection that would not pass the chroma signal, thus the reason for your B & W picture.
 
#12
FOX TV,

But it was not the Rf out to TV.

As I stated in the post, this was the "satellite in" feed line from the dish.

Signal that was corrupted on the way to the receiver produced this result. An example of garbage-in, garbage out.

When signal is too corrupted for FEC to cover up or fix errors, you may see many unexpected things.
 

FOX TV

Contributor
#13
FOX TV,

But it was not the Rf out to TV.

As I stated in the post, this was the "satellite in" feed line from the dish.

Signal that was corrupted on the way to the receiver produced this result. An example of garbage-in, garbage out.

When signal is too corrupted for FEC to cover up or fix errors, you may see many unexpected things.
I missed the point about it being the feed from the dish. I have never heard of something like this. I will have to think, inquire, and ask others, because I did not think that was possible either.
 
#14
I missed the point about it being the feed from the dish. I have never heard of something like this. (NO one had heard of this and everyone gave the answer, "It shouldn't have happened, or It's not supposed to happen.") I will have to think, inquire, and ask others, because I did not think that was possible either.
Better depend on thinking. Asking others will get you the same replies.

This little "un-answerable" question was the best thing that happened to me along this journey. It happened within the first several months of installing satellite systems and when no one would even think that it could have happened. But, I saw it and corrected it. When no one had any answers that's when I said to myself, "Well, this is pretty new and if no one else knows the science, I'll go find it myself."

I'd never even witnessed a digital picture before July 2005. I'd never seen satellite television. The beauty of beginning with no understanding of these systems (and seeing this aberration so soon) was that I wasn't sufficiently put into "the box" of all-or-nothing. Thinking out of the box is easier when you've never been put in the box!

If I had started installing satellite a few years earlier, I would probably maintain the general consensus opinion. Before the advent of HDTV, no one was even giving picture quality much thought. (Other than that digital picture was more clear and crisp than analog OTA.)

The earlier satellite systems were easily installed. They had lower signal demands, and lower noise factors, and you could do a poor install that seemed just as good as a quality install. They didn't have to pay much attention to detail in the install. This is where the idea that grounding didn't matter, R59 was ok, fittings were "close enough", and the speed of the installation was far more important than quality of the installation.

Unfortunately, speed is still the primary factor in satellite install. Since "quality" and "fast" are inverse terms, you just don't get both at the same time. HDTV is all about detail. If you don't pay attention to the details of installation, you will lose detail in your HD. Over 90% of digital function (including PQ issues) are generated at install.
 
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