Why upscale DVD on HTPC?

[JonMarsh]

I know from a variety of questions and mail I get that a lot of folks are curious as to why upscaling DVD to HD or projector resolutions can offer any benefits. If you've seen it already, you probably don't have to ask, but if you haven't seen it done properly, it's a bit of a chicken and the egg situation- there's no motivation to invest in it unless you've seen it, but if you have to invest in it to see it, you'll never do it- lacking the motivation.

I could talk theory until I'm blue in the face, and for those already familiar with Nyquist theorem and it's consequences, I'd be preaching to the choir.... the rest, it would still be falling on deaf ears, or blind eyes.

So lets go with pictures, specifically some rather good examples prepared by Bjoern Roy, illustrating from an actual image block in the Superbit version of "Fifth Element" how upscaling affects DVD playback quality. Without adding any information.

Take a gander at this image, which is two representations of the same clip from the screen....




Just what do we have here? Well, I'll start off with some clues- the bottom half of the image is a respresentation of the pixel data from a finely detailed portion of the image, at the native DVD resolution of 720X480P, "zoomed" to the same image size as would occur without any scaling or filtering functions as available in PC video cards. Just the raw data off the overlay.


What happens when we try scaling this up this data to higher resolutions availabe with an HTPC and projectors or presentation monitors?





800X600


This is 800X600, the standard resolution for SVGA projectors, and one a few large screen TV's will handle. It's also a snap for presentation monitors like my 30" NEC direct view.






1024 X 768

This is the same picture clip scaled to XGA, widely used in laptops and presentation projectors, and an easy resolution for 7" gun CRT projectors as well as presentation monitors. The text is less blocky than the "native" resolution, but perhaps the improvement isn't really "dramatic", yet.





1280 X 720P

This is scaled to 720P, the "progressive" HDTV format, and my favorite for widescreen material on my NEC presentation monitor. The text is much more readily recognizable and easier to read. There's a whole new family of digital projectors being released based on the HD1 and HD2 chips from TI; plus popular projectors like the Sony widescreen models (10HT, 11HT, 12HT, HS10) handle this OK. The InFocus Screenplay is one of the most interesting new models in this range, as will be the Toshiba variant, the HT8.





1600X900

Hi res CRT displays are flexible in displaying a wide range of resolutions, and both CRT projectors and wide screen monitors do well with 1600X900; this is the maximum usable display size for Radeon video cards, whose video overlay size is limited to 1600 pixels; at higher resolutions, pixel doubling occurs, and the effective video overlay resolution is cut in half.





1920 X 1080i

Last, we have the upper end for HD resolution. This is an option which is pushing the limits of available display technology; fully realizing this requires a top flight CRT display (9" tubes) or the next generation of LCOS and DLP displays (due out in 2003). Or a good desktop computer monitor in the 21 - 24" range, such as a Sony FW900. However, even one of the direct view "monitors" such as the new Thomson/RCA flat screen HD monitors, though not capable of fully resolving this signal, will create a pretty amazing picture compared with what most viewers are used to seeing- especially RPTV's with average (read: bad) convergence.

In real life, with a standard 720X480 display, the edges will be softer at that resolution. But there won't be any clean interpolation or upsampling such as the filtering algorithms in the best of the modern PC video cards can supply (Radeon, nVidia NV17).


Which would you rather have?







As you might have guessed by now, the upper image is an actual shot off the screen (CRT front projection) at 1920X1080.


Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Jay Sylvester]

Just wanted to thank you for this post. There's a bit of a debate going on over at AVS in one of the projector forums over the necessity of 1920x1080 digital projectors given the relative lack of HD source material when compared to DVD. This post helps prove that while DVD is the most prominent source out there right now, projectors with 1920x1080 panels are still justified when paired with a good scaler (either internal or external), even if the source isn't HD.

[Lex]

Amazing post Jon, thanks!

Lex

[Andrew Pratt]

once again the old adage a picture = 1000 words holds true. Thanks Jon.

[George Bellefontaine]

Excellent post, Jon.




My Homepage!

[Clive]

Great Info man, great info!!




CLIVE




HEY!! Why buy movie tickets when you can own a Theater?

[David Meek]

Jon,

Now you've done it! After seeing this oh-so-informative post, what choices are there for those of us needing an external scaler that will output up to 1280x720P? I've chosen a non-HTPC path and yes, a Faroudja would be nice, but not in this lifetime I'm afraid . . . budgetary constraints you know.




David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

[Chris D]

Truly one of the more useful posts I've seen on a forum. Thanks for this info! Now I've got something concrete to show the wife in the front PJ sales pitch...




CHRIS
Luke: "Hey, I'm not such a bad pilot myself, you know"

[JonMarsh]

Hi David!


No HTPC? Well, you know, those puppies come in a lot of different flavors... what if you literally just used the HTPC as a scaler/deinterlacer, with standard video sources? You don't really need a lot of processing power- current PC's are way over the top for the most part, even when using an internal player. (my HTPC running XP pro clocks in with less than 20% CPU utilization when playing back AOTC).

What I'm getting at, is even an old lowly BX board PC with a Celeron CPU, combined with the Immersivetek Holo3D capture card (with a Faroudja DCDI chip, no less, and a high grade video ADC) will do a great job of scaling with a budget Radeon or Nvidia NV17 platform video card (Geforce 4 MX 420 or 440). It has composite, S-Video, and component inputs. It does a great job with video as well as film based inputs. SRP is $895.

Both the Radeon and NV17 boards have nice multi-tap scalers. They do a visibly better job of upscaling DVD than most of the built in projector scalers, including a friend's Sony 10HT I setup with an HTPC. The latter has good down conversion, and works better with a 1920X1080i signal or 1280X720P- it looks better fed from an HTPC running 1280X720 than 848X480P- we tried it both ways- the latter results in a funny kind of subtle crawling blocking (the pixelization some report, I think).

Trying this route, the PC is almost free (just needs to have a free PCI slot, and AGP for the main video). And the result compare very favorably with the $5K and up Faroudja's.

Makes ya wonder a bit, doesn't it?

There are a few good "budget" de-interlacer/scalers, like the Centerstage CS-1, which can output a large number of different resolutions, including std. line doubling, tripling, etc., plus conversion to 1920jX1080i or 1080p.

http://www.focusinfo.com/products/centerstage/centerstage.htm

SRP is $1995, and for what it offers, it's a bargain. The CS-2 offers some additional capabilities for $500 more. Anything else more comprohensive is going to be more money, of course.

Word I've heard is that the CS-1 and Cs-2 are quite comparable to the Faroudja NRS scalers in overall performance, but with the added advantage of multiple output formats supported in each box, and more available through software downloads.

Not "cheap", but high bang for the buck.

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Chris D]

Jon-

Again, good information from you as always. I've been highly thinking about going the same route you just described, using an HTPC strictly as a scaler for existing components and not really as a SOURCE of video. The capture card you described seems to be right up the alley of what I would need.
:?:

I might as well pose a question here to you and everyone else about this: How would a standard video signal (480i or so) upconverted through a HTPC scaler to a resolution like 1080i compare to a video signal that was shot at 1080i from the very beginning? Any differences?




CHRIS
Luke: "Hey, I'm not such a bad pilot myself, you know"

[JonMarsh]

Hi Chris,

You'd have to qualify what you mean by "480i". The reason I make that statement is that there are large qualitative difference between a DVD 480i interlaced video signal from a good player versus a composite or S-VHS signal from a VCR, DSS, LD, etc. A big factor is the difference in Luminance (B&W) and Chroma (color) bandwith.

Conventional NTSC sources in composite have quite limited Chroma bandwidth; then, the necessary decoding of the Y/C signal often introduces further artifacts (dot crawl, banding, edge ringing) with anything less than the absolute best 3D digital filters. (one thing the Sony VPL-W10HT does have in it is an excellent Y/C filter- composite laser disk sources never looked better than what I've seen on a 10HT). S-VHS has about twice the chroma bandwidth as composite NTSC, but it's still under 100 lines. Component video really improves on this, (which is how the DVD signal is stored, in YUV format), but still it's a reduced bandwidth mode, so you still only achieve about 240-300 lines of color resolution on a DVD player signal.

Furthermore, 480i signals must have vertical temporal filtering to reduce line twittering and other problems- this does reduce the effective vertical resolution further compared with what would be possible with a true 480P format.

The big advantage of a good scaler is that it is essentially upsampling and smoothing the video samples with a precise mathematical interpolation, both vertically as well as horizontally. This allows the most accurate recovery of the information which is there. Note, if you look at the images above, if the HF filter on a standard DVD player is carefully designed, you can get a nice smoothing funtion on each horizontal line, but there would still be no vertical smoothing or re-sampling.

Have you ever seen a good HD source on a good display? The extra chroma as well as luminance resolution over HD is striking. Unfortunately, that's sometimes harder to find than you might expect. For example, at several Best Buy stores, I've been in there when they had over half a dozen RPTV's being fed an HD signal, and none of them were adequately converged to render an NTSC signal accurately! This is a problem with RPTV's; they do require careful setup, and they're mostly not very good out of the box. (I speak from experience, regarding the Toshiba RPTV I bought a few years back, and gave to my daughter after calibrating with the factory service menu).

What I did find in one case was that an RCA 38" direct view set outclassed all the RPTV's in the store, simply because it is inherently converged. Although the phosphor dot pitch limits true resolution to about 1200 X 600, it nontheless could deliver a very nice HD image. The last couple of times I was by that store (local), the HD direct views were being feed the same standard definition signal as the NTSC direct views, so it wasn't "upstaging" the badly setup RPTV's. A good HD signal on a good display IS better than DVD; but DVD is at it's best (IMO) scaled up properly on an HD display. Remember, DVD luminance goes all the way out to 6.75 MHz, whereas the theoretical NTSC limit is 4.5 MHz, and cable carriers typically filter their signals down to VHS bandwidth - 2.2 MHz.

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Chris D]

Wow, Jon... 8O I'm overwhelmed. Good info again. Thanks!




CHRIS
Luke: "Hey, I'm not such a bad pilot myself, you know"

[George Bellefontaine]

Yeah, I really believe Jon overwhelms most of us here at The Guide. Whenever I see one of his posts I click on knowing full well it will be some kind of a learning experience.




My Homepage!

[SteveG]

With a tip of the Hatlo Hat to Bjoern Roy.




Steve Goff