Originally Posted by bizeesheri
Looks good. When I wonder how good the HD looks, I quickly change the channel to the SD just to remind me.
Can someone explain why the PBS station (I'm getting all my HD OTA), looks SO MUCH better than the networks? It just seems to really jump out at me more than the other channels. In fact, I watch more PBS now because of it.
I agree with your observation that our KTNW-HD ch 31.1 seems to have a better picture more of the time. I don't claim to have all the answers, since KTNW has a sub channel and is not devoting the maximum data bits to picture quality. Thus other factors are involved. I can share a few such factors that I have read about.
First is the picture quality of the source material they broadcast. In a number of cases, especially movies and reruns of older material, a digital copy must be made from film or even videotape. Taking the film example, each frame of film must be digitized, just like you would scan a photo into your PC. Since film runs at 24 frames per second, as scan resolution goes up, it takes longer and thus costs more to create a digtital copy of a movie or TV program at maximum HD quality. I have read of cases where networks and HBO etc. have apparently used such digital masters created for DVD production, which are NOT as high a resolution as HDTV. If they just upscale such DVD masters instead of paying for a new HD digital master copy of the movie, we see the result in HD as "soft" resolution.
Second, HDTV camera lenses vary in quality. HD broadcast lenses used to cost several hundred thousand dollars each! Prices are coming down now, so better lenses are more likely, but a lot of cheap ones are probably still around. So some production companies may be using cheaper HD lenses on their cameras than others, and this shows up in the finished product. Portable HD cameras used in the field are almost certain to have lower quality lenses, since good HD lenses are large and heavy and not very portable. I have seen sports broadcasts that still are using old SD cameras for some of their cameras, and quite often still use SD equipment for "replays" that is just upscaled to HD. Resolution is not the only factor, since contrast and color accuracy are also very important in lens design, and and to get good blacks and colors costs money for a good lens.
Lens quality is quite obvious in the consumer digital cameras on market that advertise "5 megapixel" chips, but put cheap lenses on the camera that don't even have 2 megapixel resolution. Look at any catalog of high end digital cameras with interchangeable lenses and you will see lenses costing hundreds or even thousands of dollars to fully utilize the resolution of 5+ megapixel chips.
Third, I have read that some stations use analog equipment to insert their ads into the HD program from the network. In some cases they may convert the network HD digital stream to analog, insert their analog TV ad, and then re-digitize and upscale the mix back to 720 or 1080. If they leave this equipment in the loop and have D to A and A to D conversions even during the HD programs, picture quality loss is inevitable. Since KTNW-HD is not inserting local ads, perhaps this may be a cause. IF the station Logo appears down in a corner of a HD network program, I wonder how they superimposed that logo locally and are they using fully HD compatible digital mixer equipment to do that logo insertion?
Finally there is compression. We see a program after a long chain from the source to our HD sets. This chain may include wires, fiber optics, satellite and microwave links. Each has a bandwidth limit, and most are sending more than one program stream over the system. By compressing the data more they get more programs onto their transmission at the same time- read more revenue!!!! The temptation is to shave bits off the signals of everyone.
I think it boils down to human management decisions which balance picture quality vs. quantity and reducing picture quality often means more revenue. Since PBS is not a profit making organization, perhaps the pressure to shave quality is not as strong on the PBS HD network. Since most people are still watching network programs in SD on old analog sets, some in in broadcasting may decide, "why spend more money" for just a few HD viewers, since they will watch our program anyway?
It takes management commitment to get maximum quality. I see this in DirecTV's HD channels where HDNet and HDNet Movies ( run by HD promoter Mark Cuban) and HD Discovery channels consistently have better picture quality than the others most of the time.
I am sure no one on this forum is guilty of the following causes of poor picture quality, but a survey of people with "digital" cable found over half thought they also had HDTV on an analog TV! Many people buying HDTV sets do not connect them to the HD inputs, or even subscribe to HD program material and then complain that HDTV is not "any better", so a lot of education of viewers on how to connect HDTV is still needed. That is where forums such as this will help.
I am sure there are other factors, and even corrections to my understandings, so I welcome other posts.