Q&A # 25 - August 19, 1997
Staff
Q If DVD allows video resolution of approximately 500 lines, won't it be obsolete once HDTV is here allowing twice that resolution? Are
the DVD players "forward" compatible and able to play discs of higher
resolution, or are things fixed in the compression algorithms not allowing
this? Aren't all those new DVD movie releases going to be "low resolution"
as well; should people wait before compiling a library?
A You brought up one of my pet concerns about DVD. As far as I know, the current DVD players will not be forward compatible with HDTV. NTSC uses 525 horizontal scanning lines (called the vertical resolution), with PAL having 625 in Europe. This requires 15.75 kHz scanning frequency (for NTSC), which is derived by multiplying 30 frames per second time 525 lines per frame = 15,750. HDTV has 1,050 scanning lines, and can be interlaced at 31.5 kHz or non-interlaced at 63 kHz. They will also have more than 1,000 lines of horizontal resolution (vertical lines on the TV screen), compared to 230 for VHS, 330 for NTSC broadcasts, 420 for LD, and 480 for DVD. This amounts to about 4 times as much picture information on the screen with HDTV as compared to even a current DVD image, let alone regular broadcast NTSC! I have seen HDTV images at the CES in Las Vegas, and they are fantastic. The DVD players of today are set up to handle NTSC or PAL, but not the high scanning frequencies of HDTV. And even if they were, it is as you say: the DVD movies coming out now will be obsolete when HDTV hits the US market. HDTV is already available in Japan and Europe. DVD has the space for HDTV. It would require using both layers and both sides for some movies, but that would be fine with me, and I'm sure, everybody else who is a DVD fan. I really would not mind having to turn the disc over, and it probably won't be very long before DVD players are available that will automatically play both sides, just like most LD players do now. Lastly, even though there won't be a lot of HDTV programming for a while (it starts in the USA sometime around the Fall of 1998), I would have been delighted to just use my HDTV mostly for watching DVD movies. The problem is that numerous companies are developing the various technololgies, and no one wanted to wait until ALL the new audio/video technologies were ready for integration. The first
software available for HDTV will be UHF broadcasts, which have already
begun testing in various cities. The current Japanese system is called the
MUSE system, and it is analog. It is already obsolete in Japan, and they
are moving to a digital system like the US has. The DVD resolution is not 500 lines, but rather, it is 480 because the bandwidth of the D1 master is 6 MHz. (80 lines per MHz x 6 which = 480)
Q I have a pretty good home theater setup, but I want better. I have a 40" Mitsubishi TV, Meridian surround pieces 518, 519, 562V, and 565 with AC-3 and DTS. Acurus amps 2x250 and 3x200. Velodyne F1800 sub and Snell THX LCR
500 with dipole in back. I cannot have speakers higher than 25 inches in
front because I have a cabinet. How much better will the new Wilson Audio Cub
speakers sound? Also do I need Krell or Meridian amps? I am 90% video
listening. I want the best, but will this upgrade be worth the money?
A It appears to me that you have excellent equipment already. Unless you have heard the Wilson side-by-side with the Snell, it is difficult to say whether or not one would sound "better" than the other. Both of the these manufacturers make very good products. At this level, "better" is more likely to be a measure of your preference for tonality, rather than one of distortion. Movie soundtracks are not quite the same thing as music on a CD, and since you seem to have plenty of power in your Acurus, I would say you do not need to move on to Krell or Meridian power amplifiers. If you were using them for 90% CDs instead of home theater, perhaps you would hear more detail with the Krell and Meridian, but for home theater, probably not. The Velodyne F-1800 certainly would make up any difference in the ability of your power amps to handle intense bass. So, maybe consider some room treatments instead. Something on the wall behind the TV, and corner tunes to help reduce boominess. Next year (1998), we are supposed to have HDTVs introduced into the US, and they are going to be expensive. Save your upgrade dollars for that. HDTV images are spectacular, and I plan to be there when they open the doors to begin selling them.
Q What's special about coaxial digital cables? How are they different from RCA audio interconnects? Can I use a Monster composite video cable to make a digital connection?
A Digital coax cables are 75 Ohm impedance, while most audio coax cables are 50 Ohms. We tried a 50 Ohm audio coax to connect a CD transport to the DAC, and it sounded terrible. However, there are some audio cables that state a 75 Ohm impedance, and if your Monster cable is 75 Ohm, it should work. The final verdict, though, will be in the sound quality.
Q I would like to mate four NHT SuperZeros or SuperOnes to Bob Carver's Sunfire subwoofer. What do you think and what is
the best cross-over frequency?
A The SuperZeros respond down to 85 Hz, and the SuperOnes down to 57 Hz. I would suggest a crossover for the sub at 60 Hz for the SuperZeros and 45 Hz for the SuperOnes. This will allow for overlap of the slopes from the speakers and the subwoofer. Either speaker model should give you good results, but the larger mid/bass driver of the SuperOnes will allow you to listen to the sound at somewhat higher SPL without mushiness. Your decision to get some modest speakers with a powerful subwoofer is excellent. Deep bass is very important to the home theater experience.
Q I am currently mulling over the purchase of a data-grade front CRT video
projector that scans horizontally from 15kHz to 64 kHz, and can
project
1280 by 1024 pixels (RGB). I want to be sure that the purchase of
this
expensive equipment will allow me to enjoy all of the future HDTV
formats include 1080i, which is the highest resolution interlaced
format. In addition to scan rate and line resolution concerns, this
projector has a 5-pin RGB connection that is touted as being able to
receive future HDTV video signals. As this point, does anyone know
what
the future HDTV video connections will look like? Five connectors for a
single HDTV signal seem like a bit much.
A Data and Graphics grade projectors will be capable of playing most, if
not all, HDTV scan rates. HDTV will likely require 5 connections like
today's line doublers and quadruplers. Red, Green, Blue, Horizontal Sync,
and Vertical Sync are your 5 connections. But instead of running 5 individual cables,
they probably will decide (I hope) to use a computer type plug on the end with multiple pins.
Q I have a Mitsubishi VS-5081 RP Television, an Angstrom 200 Entertainment
Director,a MSB Gold LD Player, an ADA PTM6150 AMP, NHT VT-2 and VS-2
as
well as
Triad Gold Surrounds. I am planning on purchasing a DVD player with
component output
and would like to know how I could upgrade the TV to component input as
well as the Angstrom 200. If not the TV, then how could I upgrade the
Angstrom to S-Video which only has composite output? If this can be done
will there be a significant improvement?
A I have spoken to many TV tweak experts, and it does not look like adding a
component input to a TV would be feasible, or at least, it is just not being done at this time. Perhaps MSB Technology would be able to do this, but it would not be cheap. They are
offering a DSS receiver with component outputs at $3,000!
You might want to contact Angstrom directly about adding an S-Video
switcher inside their unit. If you add one to it yourself, it would probably
void their warranty. I recommend getting an external switcher. Sony,
JVC, and Entec (Monster Cable - coming soon) have Video switchers that
do a good job. It is always best however to run the video straight to
the TV rather than through any switches, such as there are in receivers.
Q What are the differences between the three most common digital comb filters: 1) Digital Comb Filter; 2) Digital 3-Line Comb Filter; 3) Digital 3D Y/C Comb Filter.
A 1. A digital comb filter is one where the signal is routed through an A/D
converter, then the separation is performed in the digital domain, and then
the signal is routed through a D/A. If the A/D is not clean, this is a step
where the picture quality can be degraded. The good news is that most such filters do a
good job in this area.
2. A line 3-comb filter is also called a 2D digital comb filter. Both the
Faroudja and Audio Alchemy filters are this type, and most other digital comb filters
are this type. The process looks at the previous line and next line to
determine what is the best way to separate the Y and C. Hence 3-line.
3. A 3D filter is a temporal filter. What it does is look ahead at the
next field. (there are two fields for every frame of video, one field is the
odd # lines and the other field is the even # lines from 1 to 525.) It then
compares and separates accordingly. The problem with 3D filters is
determining when to do field (3D) or line (2D) level comparing. The logic
here is far from perfect and often introduces decoding errors. It works
great on static images, but when there is motion, it must revert back to a 2D
comb filter. So a 3D filter is both a 3D and 2D filter in one. Because of
the cost of memory required to do 3D filtering, they often cut costs on the
2D portion, which, unfortunately, does most of the work.
Q I would like to know if there is any difference between component outputs of DVD and RGB? Are the two actually the same thing?
A They are different! RGB is Red, Green, and Blue. This is the most raw
form. Component is Y = Luma, R-Y (Red), B-Y (Blue). Component is a matrixed
version of RGB, and it allows the signal to be sent far, requires less
bandwidth, and can "easily" be converted back to RGB, with virtually no
loss.
� Copyright 1997
Secrets of Home Theater & High Fidelity
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