Here is the Digital Myth stated in several ways:

   "There is no variation in digital picture quality due to signal strength."

   "Digital signal is an "all-or-nothing" proposition."

   "You either get the picture, or you don't. The picture quality doesn't change."

   "If you have lock, you'll have the best quality picture available."

These statements are all false.

The digital all-or-nothing idea was begun as a way to market the newer, more expensive, digital technology. What began as marketing has become "science". They contain misinformation gleaned from the marketing not science.

THE Digital Myth - Exposed!

The truth about HD televisions, receivers, and digital systems, is that they are capable of producing a stable, but lower quality picture. At times a lower resolution picture is presented. Your picture may look blurry, grainy, blotchy, and be lacking realism. It may also look like enhanced definition instead of high definition.

This is the truth, the digital science related to signal strength and signal processing. 

If the incoming signal is too low, your digital TV or receiver can still produce a picture of degraded quality. The degraded picture may be great by yesterday's standards, but due to the limited amount of information provided by the low signal, the picture lacks much of the detail that defines high definition. (Standard definition digital picture quality can degrade, also.)

Opponents of this idea (that digital picture quality varies) often site that Forward Error Correction (FEC) takes care of all the errors.

It has taken years to find easy and understandable documentation about the signal quality and picture quality connection. Thankfully, you no longer have to read and understand my digital science explanations!

What no one wants you to know is that digital picture is not only variable, it is HIGHLY variable. The ability for these changes is written into the Forward Error Correction algorithms! We've been deceived again.

I found this article from:

 "Overview of the Scalable Video Coding Extension of the H.264/AVC Standard"

(Let me just add here that the previous name of SVC scalability was SNR scalability. That's Signal-to-Noise Ratio Scalability.)

The abstract states it very simply:

Abstract—With the introduction of the H.264/AVC video coding standard, significant improvements have recently been demonstrated in video compression capability. The Joint Video Team of the ITU-T VCEG and the ISO/IEC MPEG has now also standardized a Scalable Video Coding (SVC) extension of the H.264/AVC standard. SVC enables the transmission and decoding of partial bit streams to provide video services with lower temporal or spatial resolutions or reduced fidelity while retaining a reconstruction quality that is high relative to the rate of the partial bit streams. Hence, SVC provides functionalities such as graceful degradation in lossy transmission environments as well as bit rate, format, and power adaptation.

And,

Index Terms—H.264/AVC, MPEG-4, Scalable Video Coding (SVC), standards, video.

Read it for yourself! Very interesting! http://ip.hhi.de/imagecom_G1/assets/pdfs/Overview_SVC_IEEE07.pdf

And check here: http://en.wikipedia.org/wiki/Scalable_Video_Coding

or look here http://www.chiariglione.org/mpeg/technologies/mp04-svc/index.htm says:

Quality scalability in SVC (also known as “SNR scalability”) can be seen as a simple case of spatial scalability, where the prediction dependencies are applied between pictures of same resolution, but different qualities. 

If you would like more information read on:

   Signal Science - A Rebirth - Visit the science behind digital receivers.

   Signal Strength Meters and BER - How this works on your receiver's meter.

   Impaired Digital Picture - Other causes

   Real World Proofs - Still not convinced?

   Why haven't we heard of this before now?

   Picture Quality Observations - Observations from the field.

   Digital Science Links - Links to learning resources, papers, files, and websites to increase understanding of digital workings in the new millennium.