DirecTV, HDTV, and the Resolution Question
If you all don't remember way back in 2004 a DirecTV customer filed lawsuit saying that he had signed up for HDTV service and was soon getting sub-par results. He claims DirecTV is engaged in unlawful or fraudulent business practices by not delivering actual high definition signals. As most of us in the audio/videophille world know DirecTV started cutting bit rate and then scaling down the resolution of their HD feeds to squeeze more bandwidth. This quickly became known as "HD-Lite" in videophille circles. The drop in bit rate resulted in exacerbated MPEG2 mosquito noise, and posterization. DirecTV's odd 1280x1080i feeds resulted in a softening of the image as the horizontal detail was lost and then stretched back out at the satellite receiver to 1920×1080.
This fella's lawsuit finally came up on the docket on September 20th when a judge ruled against DirecTV's request for arbitration, meaning that this will at some point go to court and be settled by a battle of lawyers.
This lawsuit raises an interesting question: Just what constitutes high definition television?
This question has been asked in another field of the A/V world: Plasma TV's.
In the Plasma TV space one of the most common pixel matrices for mid-range "HD" plasmas is 1024×768. One might stop and wonder how is this HDTV? To be called HD requires at least 720p (1280×720) which is 16:9, right? Well the 16:9 part is taken care of, you see these TV's have rectangular pixels, not square, so they are longer then they are tall, the pixels themselves are 16:9 so you have 1024 but it is wider then you'd initially think. However the astute observer would say "yes but that still only has 1024 pixels of actual resolution!" and you'd be right. However depending on who you ask this may or may not matter. If you check the ATSC specifications you'll see only two proper HD resolutions described specifically as 1280×720 and 1920×1080. However if you ask the CEA (Consumer Electronics Association) of America, they rather liberally define an HDTV as a device that can display 720 lines of resolution or more. Notice the key here is the total lack of pixel configurations or specific resolutions? So the argument these Plasma TV vendors make is that the association of consumer electronics that helps define their industry only says "720 lines" and the Plasma has 768 lines so it not only meets but beats the minimum to be defined as "HD".
So if you stick with the CEA's description of high definition then DirecTV has done nothing wrong. The vertical resolution of the digital TV feed (1080 lines) is intact. But is that all there is to the HD equation? Perhaps from a display device standpoint, although I would argue that 1024×768 Plasma's don't make the HDTV requirement.
However from a broadcast signal feed standpoint there are defined ATSC standards for bit rate as well as resolution. 19.2 Megabits per second is the accepted bit rate for high definition ATSC MPEG2 Transport Steams. Likewise the accepted resolutions for ATSC are 1280x720p/60 and 1920x1080i/30. While there are other variations of frame rate for 720p and 1080i these are the two widely used for actual broadcast.
So if DirecTV isn't sending a full 19.2Mbit/second stream is that high definition? Well to be fair not all of the 19.2Mbit stream is A/V data some of it is padding, error checking data, etc. When stripped down the A/V data is probably more like 15Mbit/sec. So this raises the question when does dropping the bit rate go below high definition? Likewise when does dropping the resolution go below high definition?
The second question I think is pretty clear: when you go below the established pixel layout for the given standard you claim to broadcast, for example: 1080i is 1920 by 1080 pixels.
The first question is quite hard to definitively answer – When does the bit rate become below high definition? I would answer this by saying when the image quality drops noticeably below what a good quality over the air ATSC broadcast looks like. After all that is the defining example of HDTV broadcasting in the USA today. This means when we start to see clear amounts of mosquito noise and posterization and certainly when consistent tiling in fast motion is observed, you have to be real careful… is this high definition?
Perhaps the best solution is to side step the whole issue and start using an alternate compression scheme that is more efficient such as H.264 or VC-1, just like the next generation high-def optical disc formats have. Broadcast is in desperate need of a better codec. Our friends in Europe have already made this move with the ratification of DVB-S2, a satellite standard that now includes H.264 as a mandatory supported codec. Reports are that the H.264 compressed streams look gorgeous. The figures for an H.264 stream of 1080i HDTV are somewhere around the 8Mbit/sec range. That is the bit rate a standard DVD uses! …and far less then the 19.2Mbit/sec of MPEG2 HDTV.
DirecTV and Dish Network are indeed moving to H.264 but the movement has been slow due to the giant installed base of MPEG2 only equipment. I would hope that they both get aggressive in making the move to an advanced compression system. And in the mean time be fair and clear: What they are offering is enhanced definition, not high definition.
To be fair cable companies are well known for pulling bit rate shenanigans on digital cable channels of both SD and HD resolution. The cable companies have a leg up: their customers rent equipment not own it; getting consumers to switch boxes is pretty easy as they don't have to pay for a new box, they just find the time to bring in the cable box to their local office for a swap. Cable doesn't necessarily have to change compression systems to get more bandwidth; going to a switched setup instead of cramming all data down the same copper at the same time will allow immense savings in bandwidth. Also moving the fiber closer to the neighborhood allows more head room per neighborhood. All things a satellite provider can't do.
I sure don't have all the answers, but I do think the compromises made by DirecTV to squeeze more channels out of a given transponder are too much. I don't think they should be charging the high prices for their HD equipment and services when what you get is less resolution and has artifacts that can severely degrade one's viewing experience. This goes for any TV provider who thinks bit starving high definition somehow is OK. High definition is just that… high! It requires more bit rate then standard definition because it has significantly more resolution.
Am I dead wrong? right on? or just mixed up? Feel free to comment.