Q&A # 234 - June 27, 2001

Staff

Q In the text describing the software decoder "Intervideo WinDVD 2000 (PC DVD software)", you say:
" We also were disconcerted by an overall stuttery quality in almost all pans, credit scrolls, etc." In the same chapter, you also say: "We ran the PC at 60 Hz". which, I assume, refers to the vertical refresh of the display.

Now, As far as I know, very few PC graphics cards are capable of genlocking their video outputs to any other clock (they are always "master", never "slave").

If that holds for the setup you used, the only way to NOT have motion artifacts like "stutter", or, more accurately for this case, "judder", is to have the software decoder genlock its decoding speed to the video card vertical frequency.

But that would more or less violate MPEG2 decoding requirements regarding the accuracy of the MPEG2 clock. It would also have a negative impact on the audio channels (pitch!).

So that would lead to the only possible conclusion, which is that PC-based DVD players produce the video frames asynchronously to the actual vertical refresh of the display, causing typical motion artifacts. Typically your PC monitor is driven at e.g. 60.1 Hz, while the NTSC video is decoded at 59.94 Hz, and the rest is obvious.

The problem would be even worse if you tried playing a PAL DVD on this setup (50 Hz on a 60 Hz display).

Assuming I am right, this means the stutter you describe is a common problem along PC-based DVD decoders, and may be very hard to circumvent.

Any comments?

A Thanks for your input. We will look into this possibility.

Q In " DVD Benchmark - Progressive DVD Player Shootout - December, 2000",  you state, " We still like the idea of the Cinematrix, and we hope that the next revision gets better. A huge improvement would be to use the Silicon Image (DVDO) chip instead of whatever one they are using."

Well, I know for a fact that Cinematrix uses a Genesis gmVLX1A-X chip. They scrape off the markings on the chip, but they can't hide that fact that the pin connections (power, ground, digital progressive output to the DAC, SDRAM connections) match exactly those of the gmVLX1A-X. They tried to sell their solution to us saying it was a custom design, superior to all others, blahblahblah. We got a demo unit, and opened it up to look inside. The fact that it is a Genesis chip matches with the test results you listed, showing that designs using the Genesis chips all share similar de-interlacing defects.

A We were aware of the use of the Genesis chip in that product, but decided not to discuss it. We probably should have mentioned it.

Q What is the value of 540p over 480p? Seems to me that more artifacts would be introduced up-converting to 540p compared to just staying at 480p. Like up-converting from 44.1 kHz to 48 kHz.

A There is less line structure with 540p. 480p is pretty much not enough anymore, with the big size of TVs these days. If you plug 480p into these 65" RP TVs, you will still see scan lines. The lines will be lessened with 540p. The reason you can have 540p is because it uses the same scan rate and memory as 1080i.

It is true that you may introduce scaling artifacts by up-converting 480p to 540p. The only reason they scale to 600p, 720p, 768p, 864p, and 960p is to hide the line structure.

Q Where can I find more information on building my own hi-fi speakers? I'm new to this area, and I need to find out more on good raw speakers (brand-names), good crossovers, and other stuff.

A There are lots of links if you go to Google and type in speakers, DIY, do it yourself, building. Here is a link for you to start with     http://dmoz.org/Recreation/Audio/Do-it-Yourself/Loudspeakers/. And, we have a DIY page too.

Q I recently bought a Hitachi 61SDX01B TV to replace my previous large screen TV (a non-HD ready Sony). I have been using a GE1105P DVD player which, from the research I can find, is basically an RCA 5220P in a GE branded box. Needless to say, the image quality isn't the greatest. This was especially noticeable when viewing "Crouching Tiger, Hidden Dragon" - images looked pixelated at the edges with some combing as well. I went out today and tried to buy the new, and apparently popular, Denon 2800 box, but it is unavailable until next month. I then settled on the Pioneer DV-37. I was very excited to set up and view my "progressive scan" movies. I was somewhat shocked to see that image quality was not very much better. In "Crouching Tiger" - the very first scene with the close-up of Michelle Yeoh - her nostrils don't look round but like boxes. I then threw in "The Matrix" and found the colors to be a muddy mess and the edges and whatnot were combing/blocky. I am starting to wonder whether this is due to the TV or the DVD players. Is the TV a dud or did I just happen to pick two lousy DVD players to view? Or worse, is it both? Would the compression of a 16:9 wide screen image to letterbox on a 4:3 cause problems with image quality? Should I return the whole mess and buy something different altogether?

A We tested the Pioneer DV-37, and it is a good player. I suspect this is a TV problem. However, because of all the variables here, you need to take the player to your TV dealer and connect it to a different brand of TV that has progressive scan to see if the problem persists. You also need to experiment with having the DVD player send progressive scan vs. having the DVD player send interlaced and let the TV convert it to non-interlaced (progressive scan). There is a wide variability in the quality with which TVs handle progressive scan signals, and how they convert interlace signals to progressive scan.

Q In a recent article about power cables, you write: "Note from Editor: To those of you who don't believe cables can make a difference, we sympathize, because it does seem a little like voodoo. So, in a later article, we will discuss why cables might indeed conduct in such a way as to make for better sound."

As an aspiring chef, I know that you can't create a quality dish without using quality ingredients. I believe the same goes for audio equipment, including cables. However, I also believe that the mystique surrounding "high end" cables is mostly hype. I would love to be proven wrong, so I look forward to your aforementioned article, but with some reservation. Audio reviews are never conducted in a double-blind manner, and that fact continually disturbs me.

Any scientific observation that is intended to be purely objective holds absolutely no merit unless it is conducted double-blind. Why are audio reviews so different? When reviewer Joe Smith hooks up his new $600 power cord or his new $3000 preamp, he expects to hear a difference, and so he most likely will, whether one is present or not. I can not take any review seriously (regardless of the experience of the reviewer) unless that possibility is systematically eliminated, and I don't understand how non-double-blind comparative reviews have become the norm in this industry. Comments like, "I plugged in my new $1000 patch cord, and the music just came alive!" make me laugh. Nonsense like that makes a mockery of the scientific method and sounds about as convincing as a QVC salesman.

The bottom line is this: it is impossible to have a truly objective comparative review unless double-blind techniques are used. There is no way that I can bring myself to believe the voluminous rants and raves about equipment that reviewers "test" only by themselves with an A/B switch, knowing what is A and what is B. I really enjoy your site and the great information you provide, but I'm afraid I'm not going believe anything anybody tells me about cables until their test results come out of a double-blind configuration.

A I heartily agree that double blind is the best way to go, but it is a very difficult thing to set up. We did conduct a single-blind test of cables, published in 2000. The ABX test is also excellent (here is "A", and here is "B", now what is "X" [it's either "A" or "B"]?) You need a bunch of people to do the test, and most reviewers are at sites different than the main office of the magazine. So, we do the best we can with available people and equipment.

Q I have my audio /video rack next to my left main speaker and have noticed that certain low frequencies are resonating off my HTS-3500 line conditioner and creating, at times, a very annoying rattle from the conditioner's top. Is there anything I can do or buy to stop the rattling?

A What you need to do is put a bean bag or other absorbing item on top of the conditioner. You could also remove the cover of the conditioner chassis and put a small strip of thin felt between the cover and chassis.

Q I read somewhere that for the best results with multi-channel DVD-A (or SACD), you need to have exactly the same speakers in front and rear. The only difference between the Mission M73 and the M71 is that one is a floor-stander and the other one a bookshelf, but the drivers are the same. So, what is your opinion about that? What should I do?

A The best setup for DD, DTS, DVD-A, and Multi-Channel SACD is having all the speakers the same, front and rear. But, obviously this is not always possible. For starters, it is not very convenient to use another floor-stander for the center channel speaker. As long as the brand (Mission) and drivers are the same for the M73 and M71, it is very likely that these will be a good match for your 5.1 system.

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