A Discussion On Poor SD On HDTVs

rbinck

Great post, thanks.

One quick method to determine if your seating distance is too close, view the SD material in a PIP window. Many HDTVs have the picture beside picture capabilities. If the picture looks good to you and the full screen dosen't, your seating distance is too close for SD.

__________________
www.highdefinitionblog.com
www.BlogOfHawaii.com

Scottnot

Yes, interesting post for those who have not run across this information previously.

However, the foregoing doesn't really apply the "science" correctly.

The 42" diagonal HDTV does not have the ability to display 640 horizontal pixels in 4x3 mode.
This is because the TV will always upscale the input signal to display at its native resolution . . . therefore:
- assuming a 1920x1080 fixed pixel 42" display, the 4x3 mode will contain 1442 horizontal pixels.
- assuming a 1280x720 fixed pixel 42" display, the 4x3 mode will conatin 962 horizontal pixels.

In terms of visual acuity, the above are the figures that should be used.
So, the minimum viewing distance from this is not 12 feet, but rather:
- 6 feet for a 1280x720 TV
and
- 4 feet for a 1920x1080 TV

Of course, nothing is ever so simple as we would like it to be.
But using your example, if we have "the best possible SD picture from a 480p 4x3 DVD player" and if our TV also has "the best possible scaler, then the 6 foot and 4 foot results are quite appropriate.
On the other hand, if we have "the best possible SD picture from a 480p 4x3 DVD player" and if our TV has the worst scaler, then even 12 feet may be too close as the artifacts may carry over beyond the imaginary 640x480 "ideal" image reproduction.

The following chart may be helpful as well.
http://s3.carltonbale.com/resolution_chart.html

dlleno

Sure, you're saying that when the source resolution is low, a good scaler will process and present that low res information on the HD display so that the displayed result will contain additional, realizable detail that is meaningful, important, and pleasing to the eye, such that the closer viewing distance will benefit the viewer by allowing the viewer's eye to distinguish detail that was not present in the original source material. Doing this without introducing unwanted artifacts would indeed be a good thing.

As a practical matter, are you describing scaler performance that is found in today's HDTVs that are commonly discussed here, or scalers that exist external to the display? Identifying such solutions would greatly help those trying to balance SD and HD PQ while sizing the HDTV prior to purchase.

Scottnot

Yes, many (if not most, if not all) of the scalers incorporated into today"s TVs and DVD players have the capability to provide "near HD picture quality" from a "well mastered SD DVD.

My "average" DVD player and "average" HDTV are quite capable of delivering "near HD picture quality" to my eyes.

Of course, there are the "philes" and purists who will never sign up for this, but I have found that the majority on this site find this to be the case.

dlleno

Good to know. However it seems to me that there is a big difference between faithfully reproducing the SD content (via scaling) on the HD display, and adding new information to it. That is, the native resolution of the content is still SD and even if the scaler does a great job you still have no more information in the content than you started with; you've just represented it by firing more pixels. So the viewing distance measurements I was calculating were considering the resolution of the content, not the display.

But if you are saying that a good scaler will add information, and allow your eye to see detail that is not present in the source, then thats very cool indeed.

rbinck

Many people will still to this day tell you that you can't make pixels out of thin air. Well obviously that is wrong as it has been done with line doublers for years. The question is not can it be done, but how accurately can it be done.

In the simple doubler the pixels are just doubled to fill in the voids that would be missing if the available pixels are spread out over the increased resolution. In other words the pixels are just enlarged, which is what was envisioned by dlleno.

But there has been the technologies to both add spatial and temporal resolution for years. The math has been there and is has been used in still images for years. Here is a reference for a popular video processor that largely addresses spatial resolution as well as the other video processing required in today's HDTVs:
HQV Video Processors.
Now that they are going into the 120 Hz refresh rates there is a move toward the temporal resolution as well. This technology has been around for a while as well, but the speed of the processors required to accomplish temporal resolution (at live video frame rates) processing has only been recently achieved for a cost low enough to allow the inclusion in HDTVs. Here is a reference for this technology:
Temporal resolution enhancement in compressed video sequences.

__________________
www.highdefinitionblog.com
www.BlogOfHawaii.com

dlleno

bingo. that is the nature of my inquiry -- whether or not such smart scaling is here today, in the likes of HDTVs below $2K, for example, and how to know if a paticular HDTV has it or not.

Scottnot

Yes, much, though not all, is "here today" and all HDTVs have it.

Thought that is what I said in my post #124 above.

rbinck

That is where research comes in. Deinterlacers in 1080p sets, for example, you would think would be of the highest technology available since they fetch a premium. That where I was at until I was made aware of 1080p sets that fail the deinterlace tests as well as the 3:2 cadence tests. For more info see: The 1080p HDTVs particularly the links at the conclusion.

__________________
www.highdefinitionblog.com
www.BlogOfHawaii.com

Zaphod

I tried sitting farther away watching SD and it did make a difference. Makes sense that you need to sit closer with HD to pick up the detail but causes a quality problem when watching SD. Good post Dlleno

Scottnot

So, if I swap out my old 720p 40" set for a new 1080p 40" set . . .

does that mean that I have to sit closer???

C'mon guys . . . . . cart - horse . . . . horse - cart . . . .

Mike999

Cable channels undoubtedly utilize much better upscaling equipment than a typical HDTV, and yet most TV viewers can easily distinguish upscaled content from true HD programming. In fact, a lot of upscaled content - especially filmed material - actually looks far worse than the standard cable equivalent viewed on a SD CRT. Again, if upscaling really led to "near HD picture quality," movie studios would not be investing millions in Blu-Ray transfers.

After much observation, I've come to the conclusion that upscaling can lead to "near SD picture quality," but only when the material being upscaled is nearly perfect. Analog or compressed video, low bit rate DVDs, out of focus camera shots and the like don't upscale well, and image quality decreases exponentially as the quality of the source decreases.

If you watch nothing but HD-mastered DVDs of recent Hollywood action movies, then you're probably not going to see much loss of quality with upscaling, assuming you have a decent HDTV and you aren't sitting too close to the screen. If, on the other hand, your DVD collection consists of older transfers of old movies and TV shows, or if you like watching newscasts, then upscaling will definitely result in a loss of image quality compared to the PQ on your old CRT.

HDisGoodMan

Anyone have the highly-rated Samsung LN40A550 or LN46A550 ? I'm wanting to buy this set in the next few days, but I'm worried about how SD content will look when upscaled to 1080P. That's alot of pixel interpolation ! I have a 720 XBR Sony LCD from a few years back and cable SD looks fine from my viewing distance of 10 ft. Any advice ? Thanks !

dlleno

yea I guess actual results depend on the display and the eyes watching them. I haven't seen it, but what I'm hearing here is that fancy up-scaling can add enough detail to a low-res source so that when it is rendered by a high-res display you really do see additional detail, for example distinct blades of grass that were not in the original source, facial features, sharp edges and distinct lines, etc. and that this upscaling allows you to sit closer than my minimum distance calculation (using SD resolution) would predict. It would be nice if the magic would apply to SD source content coming from Sats too!

joekewl1971

I think the black (brightness), and white (contrast, or picture) levels are very important to reduce artifacts. The brighter the picture, the worse it looks. Bring the black down, and you see what detail there is to see.

Beauty is in the eye of the beholder. So they say. Everybody will have thier own opinions. I disagree with some of the things I have read in this thread. That is right for me. It may not be right for everybody. Technical advice only goes so far. There is no substitute for looking at the TV to determine if you will like it, or not. You try it one way for an extended period of time. Then you try something different for an extended period of time. I looked at both interlaced and progressive scan before choosing progessive scan. That took me a long time to decide which I liked best.