Part 5: DVD TRICKLE DOWN:
 
Why We Have To Wait For Technology
 
©1997
 
by
 
Eddie Ciletti
 
At the time this article was written ó 1997 ó DVD was already a year behind schedule. As of summer'98 Video, however, titles are in the stores.  I now own the Panasonic SV-310 DVD player.  It has stereo and surround outputs (both analog), SPDIF (for standard CDs) and DTS (for an external decoder) as well as composite, component and "S" analog video outputs. In standard configuration ó as a source for home video ó DVD delivers data-compressed digital video and 5.1 channel digital audio the latter at about 360 kbits/sec.  Audiophiles want the DVD to be their saviour.  It could easily deliver 96kHz / 24-bit stereo audio. Sony also has a dual-format disc with a standard CD layer and a high-resolution audio layer.

But alas, the audio biz is just a small slice of the technological pie. Thatís why we are at the mercy of our favorite pasticceria: consumer electronics. This means that professionals ó specifically in the audio field ó reap the benefits of consumer technology as it trickles up, rather than the other way round.  Take DAT, for example. A failed consumer-oriented product ó it survived the battle of lawyers, record companies and government. (The acronym SCMS ó that annoying copy protection scheme pronounced "scums," seems more than appropriate here.) Had DAT penetrated the consumer market, the machines that we use would cost about half as much. (Think about the price of a VCR!) For this reason, it is in our best interests that DVD succeed because as a market success story, it can deliver more sonic gain with less financial pain. (Projected prices for initial DVD players for computer use will be $1000.)

There is one more point I can only touch on briefly.  Because Dolby and DTS and Sony are all vying for a slice of the DVD pie, it's the format wars that are holding back the format are about licensing.  Everyone wants to be the default format because, for example, every audio and video tape with the Dolby Logo and every piece of hardware with Dolby decoding chips returns a royalty to Dolby.

MORE THAN JUST "SLEIGHT-OF-HAND"

Advances beyond the current state of digital recording ó improved bandwidth and real time signal processing, for example ó have been hampered by the simple fact that the most available and affordable DSP chips are also those used for consumer electronic tasks like Surround Sound. For both shear enjoyment and as a mixing tool, Surround is a personal favorite. But if you didnít know, it is also just an audio card trick.

In its most basic form, Surround requires four identical monitors that can be connected to any stereo system with a simple wiring variation (visit http://www.tangible-technology.com). All of the brand-name accoutrement are no more than sleight-of-hand stereo with "steering/logic" (computer-assisted panning) and delay, not four discrete channels. Why DSP is involved Iíll never know. Do consumers really add reverb to their tapes and CDs?

WHATíS IN A NAME?

What started as the Digital Video Disk is now known as the Digital Versatile Disk. Iíve seen the "video" and it was pixelated. Why demo a system with obvious flaws? Could it be that double-sided, multiple layer DVDs are not yet ready? Why else would manufacturers try to fit 133 minutes on the single side of a disk? Too much data compression looks about as fab as recording at SLP.

FYI, the laser disc is analog technology that has much more resolution (detail) than VHS. I donít currently own a laser disc player, but I certainly wonít be investing in DVD if the video is so obviously compromised. At present, DVD is much better suited as the designated replacement for the CD-ROM. (Players and new titles appear should be appearing soon.) Data compression is appropriate in applications such as the internet where speed and data-thriftiness is more important than accuracy.

Another failed consumer format, the Minidisc, found a place in the radio industry as a replacement for "carts," the endless loop tape cartridge used for commercials. Even with digital compression, the Minidisc will be a welcome improvement over the flaws of analog cassette tape currently used in "personal" multitrack recorders.

LETíS TALK ABOUT SEX, BAY-BEE

All right, so maybe sex is the only way I could lure you into a paragraph loaded with numbers. Table One lists the data rates for technologies past, present and future. There are four DVD options from single-sided, single layer to double-sided, double-layered. One side of a digital versatile disk holds about six times the storage capacity of a standard compact disk.
 

F O R M A T
sides/ layers
time / capacity
MBytes per min
bits per second
modems
 
 
 
28.8k, 33.3k 
& 56k /sec
ISDN
 
 
 
128 kbits / sec 
CD
1/1
73 min / 771 MB
10.575 MBytes / min
1.41 Mbits / sec 
88.2 kHz DVD audio
 
146 min / 1.54 gig
21.15 Mbytes / min
2.82 Mbits / sec
4 channel 88.2 kHz
 
146 min / 3.08 gig
42.3 MBytes / min
5.64 Mbits / sec
DVD-5 (4.7 Gbytes)
1/1
133 min / 3.78 gig
35.17 MBytes / min
4.69 Mbits / sec
DVD-9 (8.5 Gbytes)
1/2
133 min / 8.50 gig
63.9 MBytes / min 
8.52 Mbits / sec
DVD-10 (9.4 Gbytes)
2/1
133 min / 9.40 gig
70.67 Mbytes / min
9.42 Mbits / sec
DVD-18 (17 Gbytes)
2/2
133 min / 17.0 gig
127.8 MBytes / min
17 Mbits / sec
uncompressed composite video
 
133 min / 598.5 gig
450 Mbytes / min
120 Mbits / sec
 
 
 
 
 

Please note that the "average" throughput for DVD ó 4.69 Mbits/sec ó will allow 133 minutes on a single-sided disk. Using Variable Bit Rate (VBR) technology and MPEG-2 compression, DVD mastering engineers will decide (in conjunction with software) to raise the bit rate to accommodate detail (fast moving images) and lower it for nearly still images. At this rate, 133 minutes of video ó with three channels of audio and four sub-title channels ó will fit on less than 4 gigabytes.

NOTE:

From the four standard disc capacities, I extrapolated data rates that would accommodate video projects that demand greater detail using less compression.

When DVD does become available to the audio industry, it will have no problem storing digital audio. Based on the data rate for a standard 44.1 kHz CD (1.41 Mbits/sec), doubling the sample rate to 88.2 kHz will do the same to the data rate (2.82 Mbits/sec). A 73 minute classical recording will take up a mere 1.51 gigabyte of space. With a little imagination, why not 90 minutes of discrete four channel audio (3.08 gigabytes)?



 
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