Tuesday, June 9, 2009

Why did Dish Network change the signal meter? Part 2

This that a forum poster wrote recently fit right in to the second part of Why the signal meter changed so here it is.

[QUOTE=DefDude;1847431]I get a local channel 55 out of mobile/pensacola. last night I noticed that the size of the pic has shrunk down and will no longer fill the screen on any tv, HD or SD.... with any of my receivers 722,522,322. Even when I stretch or any of the zoom's, It looks like a box in a box in any format. this is one the channels I don't get OTA so my question is, does this have to do with the switch to digital, or Dish. the pic quality does look somewhat darker and clearer but I'm sure if it is because of the smaller pic or because it is now a digital signal.[/QUOTE]

It has to do with low signal strength or poor signal quality.

The shrunken picture is a type of scalability that is built into the MPEG forward error correction. Your television receivers AND your Dish receivers (Directv, digital cable) everything using MPEG has scalability, built right in.

When you have less than the minimum of 70 on a standard digital signal quality meter (everyone's meter except the new improved dish signal meter), there is built-in or rather "written" in, coding that allows for the decoding of a weaker, or compromised signal. It is called Scalable Video Coding extension, and has been a part of HDTV since at least 2005.

One of the types of scalability that is available to use, is spatial scalability. This scalability says, "Since the signal is poor and there is not enough data to produce the full size picture at the proper resolution, then I'll display the proper quality, or resolution, at a reduced size."

These are three types of scalability. They are temporal, spatial, and fidelity scaling options. Broadcasters and TV manufacturers use all three of these handy, low-signal digital tricks.

Spatial scalability is what you are witnessing on your TV. Here the quality remains but the size of the picture decreases. Dish does NOT use this type of scaling because it too easily leads to the truth of the picture/signal relationship.

Fidelity scalability is scaling that reduces the quality of the picture (grainy, blurry) but maintains size. Since most people don't see this difference, and the perpetuation of the "all-or-nothing LIE" says that signal is NEVER the problem, this type of scaling is acceptable to Dish.

Temporal scalability refers to time scalability and accounts for a good portion of the audio sync problems that are being reported. Since these also have a reputation of being blamed on software issues and such, this scaling is also acceptable.

Dish receivers use the fidelity scalability and temporal scalability, but they ditched the spatial scalability as rapidly as they could, after the release of the 811's. When the 811's came into widespread distribution, Dish decided quickly to develop the new receivers that would NOT use spatial scalability. And, they haven't used spatial scalability since.

Did you ever wonder why the 811's were so rapidly converted to 381's? With spacial scaling it is far too obvious that digital picture isn't all-or-nothing. All receivers after the 811's use coding that takes advantage of the quality (fidelity) scalability, and temporal scaling, but NOT to use the spatial scalability. Since compression and bandwidth have been getting the heat from all the "experts" concerning picture quality, Dish thought it good that people continue to blame the "technology" instead of the provider.

If this news got out, they would have to spend more money on training to increase the dish alignment skills of their technicians. Dish would also incur a greater amount of responsibility for the quality of their product because - as I've said over and over the last three years - only a dish that is at absolute peak provides acceptable quality HDTV. It appears that over many years Dish (Directv and Cable) have all been charging for avoidable service calls generated at install by their technicians.

Desiring to avoid a fire-storm of public outrage at Dish (because the picture CAN get better if only their techs were trained properly to maximize signal) they killed spacial scaling and dismantled the 811's. And that brings us back to the burning question, "Why did Dish Network change the signal meter?"

Did I answer that one yet?