Question about standard definition picture quality

[cgb2063]

Hello,

I have a question that I hope someone here will be able to answer. I have recently purchased a SHARP AQUOS 37" LCD HDTV Monitor (LC-37G4U) as well as HD service from DirecTV (the 811 dish, I believe). The HD receiver is a Samsung TS360. The problem I am having seems to be mentioned in this forum frequently, but I have yet to read a clear explanation for it. The HD channels all look fantastic on the TV as do DVDs and my local over-the-air digital channels (which broadcast in both HDTV and SDTV). But all the other SD channels on DirecTV suffer poor picture quality (PQ).

It varies from channel to channel: HBO is best and local channels are worst. The picture is not blurry or fuzzy, but suffers from blockiness and other digital compression artifacts. I understand that DirecTV (along with everyone else) is compressing their signals for the sake of more channels in their limited bandwidth. I understand that they use MPEG-2 format for their digital signal, which employs a lossy compression algorithm, similar to JPEG compression for static digital images. So it would seem that there's nothing to be done. The source itself is compressed.

But, why does the same signal coming from my Samsung receiver connected to a regular old analog TV not show any of the digital compression artifiacts? In fact, the picture looks great on a regular TV; I just tried it out comparing my HDTV side by side with an analog TV. What is the analog TV doing to the compressed *digital* (not analog) signal that allows it to look fine? Why can't the HDTV do the same thing for SD signals? Or can it?

Any answers to those last 2 questions would be greatly appreciated.

Thanks.

[SimpleSimon]

There's lots of factors.

Is the LCD hooked up digitally? Is the HD tuner outputting in the native resolution of the LCD TV? Try an analog connection just for comparison. Just guessing here.

[cgb2063]

There's lots of factors.

Is the LCD hooked up digitally? Is the HD tuner outputting in the native resolution of the LCD TV? Try an analog connection just for comparison. Just guessing here.

Yes, the LCD is hooked up via DVI and the LCD TV automatically adjusts its resolution to the input. The HD tuner is set to output the native resolution of the source (480i/p for SD and 720p for HD - I can have it also do 1080i for HD, but then there is a strange flicker in the image. Have to deal with one issue at a time).

[Nick]

Try feeding one of the SD outs from your HD receiver to corresponding ins on your display. None of the HD boxes output SD very well thru DVI or component connects. You will have to switch between HD and SD inputs on your display, but a small inconvenience should improve your SD PQ. Good luck!

[cgb2063]

Try feeding one of the SD outs from your HD receiver to corresponding ins on your display. None of the HD boxes output SD very well thru DVI or component connects. You will have to switch between HD and SD inputs on your display, but a small inconvenience should improve your SD PQ. Good luck!

Yep. Tried that too. No noticable difference. The artifacts are still there, but the whole picture is just ever so slightly more fuzzy. :(

[Slordak]

It's just a by-product of having a large high resolution display. When I watch Dish Network on a 27" analog TV, everything looks clean. When I watch the same signal on a 50" HDTV, all of a sudden all of the imperfections of the image are blown up and made visible. Every compression artifact which was previously blurred or hidden now appears. If you add a stretch mode, well, that makes things even worse.

Standard definition NTSC signals just aren't well suited for display on large televisions, since there's just not enough resolution there.

[mini1]

"the 811 dish, I believe"-Thats Dish Network's HD Receiver name, not DirecTV's.

[kb7oeb]

Some channels are just over compressed. When I used to have the Phoenix local channels on E* I felt like I was watching a streaming video over the internet. It bugged me on my 56" SD tv and my 25" tv. I ended up getting an ATSC tuner for my computer so I could PVR the digital OTA broadcasts. They looked as good as a DVD on my SD tv.

[cgb2063]

It's just a by-product of having a large high resolution display. When I watch Dish Network on a 27" analog TV, everything looks clean. When I watch the same signal on a 50" HDTV, all of a sudden all of the imperfections of the image are blown up and made visible. Every compression artifact which was previously blurred or hidden now appears. If you add a stretch mode, well, that makes things even worse.

Standard definition NTSC signals just aren't well suited for display on large televisions, since there's just not enough resolution there.

But I have seen SDTV signals from cable broadcasts on my Dad's 55-inch analog TV and the picture looks reasonable. Sure, if you sit too close you can see every single pixel, but the digital compression artifacts are not there.

My feeling is that there must be some kind of algorithm that the digital sets can do to mimic whatever it is that analog sets do.

Otherwise, why would anyone in their right mind buy a TV that costs $4K+ when 90% of the channels they watch will look terrible on it. Especially when they could buy a reasonably sized analog TV for $500. (Note: I'm implicating myself as a crazy person here.)

[hikerak]

I agree I just bought a Samsung 3275 with the built in Tuner. While I am very happy with the ota locals both HD and SD, the Locals on Dish appear somewhat fuzzy and I have the Dish plugged into the Svideo jack on the back. The other Dish channels(not local) look fine. The Locals are watchable and I keep think that I will just get used to it but I haven't, and it has been four nights.