What would you think if digital images were stored on your PC in such a way that it prevented you from ever using more than 640 x 480 VGA (the minimal IBM PC video graphics display standard)? Or stopped you from displaying images at 1024 x 768 (superVGA), and beyond? Or limited you to displaying just 16 image colors?

Obviously, this is not the case. Computer users can, hardware/software permitting, continually increase image resolution, and display millions of colors. Now think about the current DVD brouhaha. These new formats are the functional equivalent of foisting VGA-restricted graphics on the consumer. You may want better audio sound and image resolution. And you know the binary bits are all there on that DVD for this enhancement processing. But instead, all DVD vendors intend to give you is fast forward, frame seek, slow motion, and freeze frame. Real rocket science stuff.

Once you see through all the marketing-war smoke surrounding CD, DAT, DCC, DVD, etc., you quickly realize these devices are nothing more than artificially-restricted mediums for storing bits. But bits are bits, no matter how special their producer/vendor may think they are.

A bit could care less if it turns out to be a reproduced Mona Lisa or just cheap porno. It is the software that assembles and displays the bits for the user that makes the final determination as to how it all comes out. The format the bits are stored in is just an artificial contrivance; a set of conventions, for storing and retrieving the data.

As the format is only an arbitrary set of rules, these formats are easily transformed back and forth from one to another -- provided, of course, you have a general purpose, 'open' computer and the software to do the transformation. PC users are accustomed to such processing flexibility. You can readily buy add-in cards to process digital sound in 8, 16, or 32 bit formats for ever higher resolution. Ditto for video.

But instead of providing such open systems, consumer electronics vendors try to lock their customers into a dizzying array of 'closed' special purpose devices having limited functionality.

For digital convergence to truly succeed, we must move away from largely irrelevant format battles, like the recent DVD fiasco, to where the discussion properly belongs: How to intelligently manipulate the audio/video data stored on any given medium to produce the best sound/picture in your home. And without question, such consumer freedom lies in the domain of 'open' computing.

Truly open digital convergence would spur tremendous technology innovation. Hapless consumers would be freed of the consumer electronics stranglehold over audio/video technology. And just as in PC's, off-the-shelf application software would become the new king of the consumer electronics market.

Via low cost, plug and play software and open systems, the consumer gets far more product choice; a standardized, all-digital platform from which to grow; a much better performing A/V system; and easy performance upgrades. No more throwing away the whole expensive shebang just to get an incremental(and questionable) performance benefit.

The result of such open multimedia systems is no more new (and suspect) A/V format/storage mediums just to push increased sales. Instead, like PC hard drive manufactures, the consumer electronics vendors would have to provide standardized, general purpose digital A/V storage devices that are differentiated solely upon price and performance -- and not on what they may inadvertently do to the sound or video.

For the sake of brevity, let's call this new audio/video 'open PC' an APX system. And keeping with the times, let's also consider using digital signal processors as the system's CPU linchpin Why use DSPs? See the Jan. 1, 1996, issue of 21st, "Why DSPs may put Intel on the Trailer") The computer industry has shown that several such competing APX 'standards' would be acceptable, even welcome. E.g., IBM compatibles, Macintosh, Sun SPARC, etc.

Moreover, as the multimedia APX is a general purpose computer, it can use some currently available peripheral storage devices that, unlike DVD, are read/write capable, and offer as much capacity as DVD. Moreover, as it could be labeled a 'computer' device, and not a consumer electronics product, the APX could also avoid all the SCMS copy protection nonsense.

For the purposes of this discussion, let's think about the business economics of such a DSP-based APX system. Audio and video system vendors, both in the 'high end' market and in consumer electronics, could, if they wanted, act like PC vendors, and make and market the complete APX system chassis. Some of these vendors could also continue making their custom 'black art' widgets; but these are now add-in cards that adhere to the format of the computer industry's new local bus standard, the PCI (Peripheral Component Interface).

But most important, by all of the vendors relying on a standardized APX computer platform, they could instead focus on creating innovative, software-based, high performance, audio/video processing algorithms.

Once the bits are fed into the APX computer, the data can be stripped of its clocking signals, protocols, etc., and turned into a general purpose, real time data stream. Other vendors' specialized software/add-in cards could then massage that data stream, and enhance it most any way they think most effective. Presuming a 32 bit APX computer architecture, many powerful kinds of digital enhancements to the A/V data are possible.

In many ways, this consumer electronics vs. open PC scenario has already been played out in another industry. The recent shotgun marriage between the vendors of proprietary telephone PBXs and 'open telephony' PCs is a perfect example of digital convergence at work. See this issue, So Who Ya Gonna Call?


Let's Wrap It All Up In Something Hot

A couple of other important points. No mention has been made so far about the other principal component in the digital A/V chain: The media transports/receivers. The consumer electronics manufacturers somehow consider it to be in their best interests to sell you as many non-compatible format devices as possible, e.g., DCC, CD, CD-E, DAT, DVD.

So, assuming this vendor-enlightened behavior will continue, the APX has to be able to interface to all these fecund digital gerbils.

The interface solution certainly does not rest in using S/PDIF (Sony/Philips/Data Interface) nor in Toslink; two truly brain dead consumer electronics protocols for shoveling bits around. What we want on the APX is a low cost, plug and play, high speed peripheral protocol that supports isochronous transmission of data; meaning that a fixed slice of bandwidth can be dedicated to a particular multimedia peripheral; e.g., to an audio or video component.

The answer lies in the use of the new IEEE P1394 serial interface, aka, 'FireWire'. (See FireWire article, last issue, in the Impact section). FireWire is cheap, fast, supports isochronous digital audio and video, as well as computer peripherals, can be readily integrated into consumer-level multimedia transport devices, and has the backing of many of the consumer electronics giants. With FireWire, we finally have a good reason for throwing out both Toslink and S/PDIF.

Finally, let's not forget that our APX system box must also support the TCP/IP Internet protocols. For good or ill, TV cable companies will soon be bringing low cost, high speed, 10+ megabit/second Internet connectivity right into your home. So at some point in the not too distant future, you will be able to quickly download a digitized audio/video recording of your favorite artist/movie right off the 'Net, and record it onto your FireWire-enabled, APX digital recorder system for later playback.

[This type of Internet-connected 'AV/appliance' also opens the door to consumer PCs that can act as servers for automating the 'smart home.']


Some APX Application Examples

In the last issue, we discussed the coming of 3D sound to PCs. Some 3D audio PC systems work on both headphones and speakers (they are user selectable). A sensing device on the headphones monitors the listener's head position, and then renders the sound accordingly.

When listening to speakers, you can usually move your head back and forth in front of the monitor plus or minus 45 degrees. For surround sound in the home, 3D PC systems like this conjure up some intriguing possibilities.

For audio-only listening, a person is typically seated alone, in a favorite spot. Moreover, the average listener height is relatively easy to gauge. So, a smart sonar sensing device might not have such a hard job detecting the person's whereabouts in a room. The sonar data could then cause DSP-active, intelligent components to shift the soundstage to accommodate the user's listening perspective.

So, via a graphic menu displayed on your APX machine, you could dial in your favorite seating position in a concert hall, and then have the APX system adjust the 'active' soundstage accordingly.

Moreover, you could even turn your head in the direction of, say, a trumpet player, and have the sound localization as naturally shift as if you were physically there. In this listening scenario, the demands on the sensing system are probably less rigorous than in active head tracking for a fast moving VR PC game.

But the key to success in a 3D audio processing system lies in getting at the bits so they can be processed in real time by smart algorithms. Thus, digital convergence = open media formats.

Once a general purpose audio/video computer like the APX gains access to the bits, it then becomes feasible to radically shift the surround soundstage by simply changing the software program. One result can be new sound fields that readily accommodate multiple viewers for home theater/TV. This intelligent system approach makes a lot more sense than just adding more 'dumb' speakers to increase the sonic perspective; i.e., the brute force method taken by current surround systems.

If the bits become truly free through digital convergence, then it also makes the whole debate about AC3/DTS (the two competing surround sound system technologies for DVD, with AC3 being the current DVD standard), and the new 'super' audio discs moot, if not irrelevant. If you have ready access to the bits, then you simply software select various types of enhancements.

For new audio media, the best approach may be to cram in as many audio tracks packed with as much data as possible into a 'generic' format, sampled at as high a rate as possible, and then use specialized software to determine how the sound should be 'displayed' at run time. Computer users routinely do such resolution selection with their video graphics displays via system software.

To a certain extent, Sony is already developing such a 'generic audio format' system. This future product is a professional encoder (used to prepare/write the bits to master disc/tape) and will utilize Sony's new DSD, or "Direct Stream Digital" technology.

In the Sony scheme, a signal with more than 100KhZ bandwidth and 120dB dynamic range is first recorded and stored on a professional digital recorder. The data is then transferred and converted to whatever consumer release format is required. The professional recording engineer would be able to select from 44.1kHz, 48kHz, 88.2kHz, or 96Khz sampling rates; as well as choose 16 bit, 20 bit, or 24 bit precision.

A Bad Case of the Jitters?

But regardless of how the data is recorded and laid down on these new high capacity systems, like DVD, their proper playback will likely require yet another add-on utility: The user will probably want some specialized APX software which reduces 'jitter' noise. Briefly stated, jitter is caused by timing errors that creep into the data stream.

Some Background: Digital data on DVD discs and CDs is stored via pits and 'lands'. The absence/presence of pits/lands is detected via a coherent laser beam within the CD/DVD player, which scans the rotating disc. A land reflects back light, a pit does not. (More technically, it is the laser light scanning past a transition area between pits and lands that causes the signal fluctuation, which in turn is then interpreted as a change in state.) Thus, we have the basis for a binary on/off switch, or digital 0's and 1's.

[The shorter the wavelength of the laser, the smaller these pits/lands can be. And the smaller the pits/lands, the more data that can be stored within a given area. Which is why IBM was so hot to get the DVD battles over with. Its new blue lasers are of a much shorter wavelength than the lasers currently used in CDs/DVD. Thus, IBM stands to make a bunch of money manufacturing/licensing its blue lasers to the off-shore DVD manufacturers.]

If you have sloppy transitions as the signal swings from one state to another (i.e., 0 to 1), and it is not auto-corrected by the player's on-board circuitry, then you get a spurious, or time shifted, signal. This erroneous signal is the jitter 'noise'. It is a result of a data timing error, as the circuitry used to reconstruct the data for accurate playback finds itself out of synch.

Ordinarily, this DVD/CD data is self-clocking, with a repetitive pulse slotted right into the data stream. This pulse, aptly enough, is called a 'clock'. This self-correcting mechanism is meant to avoid any timing problems. But it doesn't always work. According to many in the high end audio industry, this badly timed data routinely escapes detection/correction, and can produce audible distortion, i.e., jitter.

Jitter can happen anywhere in the data transfer food chain. And if you take the point of view that music is based on time, then anything which significantly effects timing is a bad thing. Which is why audiophiles have been most concerned with the jitter phenomenon. As a consequence, numerous add-on devices are available for getting rid of jitter. Typically, they are sold into the high end consumer audio market, and often cost many hundreds of dollars.

Anecdotal evidence increasingly seems to indicate that much, or most, of the jitter in audio CDs is caused by land/pit imperfections created during the disc manufacturing process itself. See Mobile Fidelity GAIN System, this issue.

But the manufacturers are going to have get a whole lot better at it if they are to keep up with the demands of DVD. The reason is simple: There are many more land/pits packed into a square centimeter of DVD tracks than on a CD. The resulting effects from bad disc manufacturing will thus be cumulative, so there will likely be much more jitter with DVD than with the present CD format. [This will be even more true when Big Blue's tiny blue lasers arrive on the scene.]

But if an APX machine is used, there is an elegant way to combat this jitter breeding problem. Jitter in the signal can be viewed as a repeating pattern -- if it weren't somehow repeating, it wouldn't be called jitter. By using self-adaptive software algorithms (which can be thought of as a means to recognize reoccurring patterns), and then applying intelligent autocorrection 'on the fly', the jitter bug can be killed dead in its tracks. And because the jitter-killing algorithm is adaptive, it can recognize new circumstances, and act appropriately.

It should be noted that such self-adaptive systems, like those that utilize artificial neural networks, can be designed to work in real time; i.e., they can scan and jitter-correct a data feed as it streams off a DVD. Thus, an intelligent APX system could stay one step ahead of any new and unexpected forms of DVD jitter.

Free The Bits!

The computer and consumer electronics industries are now at the same marketing crossroads as the PC telephony upstarts and the old-line telephone PBX vendors once were. Like computer telephony, some fundamental issues make the shift to open consumer electronics almost inevitable:

1) The multimedia computer model works, and it is the way of the future, because it is open, and the Bits are Free.

2) The restrictive consumer electronics/entertainment model doesn't work, and is doomed to the past, because the Bits Are Enslaved, along with the consumer.

The solution is therefore obvious: It is Time to Free the Bits!

In the next issue of 21st, we see why powerful forces within the entertainment industry would much prefer to keep the bits enslaved, and how the U.S. Congress got in on their bad act.