4 PLAYBACK HARDWARE AND MEDIA

4.1 BACKGROUND ON THE LASER DISC FORMAT

The installation's audio and video use the laser disc (LD) format. Laser disc is by far the most successful and popular of the many obscure laser and stylus-based videodisc formats brought to market in the early 1970s. The LD format was introduced in 1978 by Philips and MCA and promoted as the quality home theater alternative to Video Home System (VHS) and Betamax. Early on, the laser disc format became closely associated with the Pioneer Corporation through market dominance and innovative products (the term “laser disc” was originally a trade-mark of Pioneer). Laser disc offers a measure of inter-activity since content can be indexed and played back in any sequence specified by the user. As an interactive means of presenting visual content, the laser disc format attracted the attention of educators, and many educational and cultural institutions adopted the technology.

Laser disc video is stored on 12, 8, or 5 in. optical discs. By far, 12 in. discs are most common. Discs can be either single-or double-sided, holding approximately 30 to 60 minutes of video per side (the discs in the Birnbaum piece are single-sided). From a materials standpoint, the construction of the disc is somewhat similar to that of the more familiar CD-ROM and DVD optical discs. Figure 7 shows a double-sided laser disc in cross section. The video signal is stored using a system of pits and lands impressed into a metallic layer, usually made of aluminum. The thin metallic data layer is adhered to a substrate usually made of acrylic or polycarbonate and is covered by a supercoat, protective layer. The laser from the playback device is either reflected off the lands or is scattered by the pits. The reflections from the lands are detected by a photodetector in the playback device.

While this system has much in common with more contemporary digital optical disc formats (CD-ROM and DVD), the LD video format is strictly analog, as the video signal is represented by slight variances in pit-to-pit spacing (Niland 1999). LD is a composite video format, meaning that luminance and chroma information are compiled into one signal. Image resolution for the NTSC laser disc format is 420 luminance scan lines horizontally by 480 luminance scan lines vertically and 70 chroma lines horizontally by 480 chroma lines vertically (NTSC is the National Television Standards Committee, which sets the standards for color television employed by the United States, Canada, and Japan). A typical luminance signal to noise ratio (S/N) for LD is 52. The frame rate is 30 frames per second. For the sake of comparison, the following table presents these data with that of other common video formats, including DVD (Herranen 1998).

Fig. 7.

The layers in a double-sided laser disc shown in cross section

While laser disc video is always analog, the LD audio can be one of many analog or digital formats. In practice, NTSC laser disc audio is generally digital stereo sampled at a rate of approximately 44,000 to 48,000 samples per second at 16 to 20 bits per sample. The digital sound data transfer rate is approximately 1.44 megabits per second (mbps). A typical signal-to-noise ratio might be in the range of 90–96. The output audio signal requires external amplification for playback.

Laser discs allow the stored content to be organized into separate “chapters” that can be indexed for near immediate recall. The Birnbaum laser discs contain five such chapters: one for each of the four video segments, with one chapter devoted to image and sound quality presenting standardized color bars and tones that allow for visual and aural synchronization among the monitors and loudspeakers. As each of the Birnbaum discs contains all four video tracks, the discs are interchangeable among the four LCD stations.

4.2 LASER DISCS' IMPENDING FORMAT AND HARDWARE OBSOLESCENCE

From the standpoint of physical longevity, optical discs (such as CD-ROMs and DVDs) are estimated to have a useful life of anywhere from 10 to 100 years, depending on the manufacturer, ambient storage conditions, and handling. This life expectancy compares very favorably with video stored on magnetic tape, which, given the same storage conditions, might last anywhere from 10 to 30 years (Van Bogart 1995). Unlike tape-based video, laser disc playback does not require any physical contact so the discs do not become “worn” during playback or even after long periods of “freeze frame” playback. Physical damage to the discs through handling or embedded dust and dirt are more pressing concerns, as these defects can alter the path of reflected laser light upon playback.

While laser discs are relatively stable given proper storage and handling, the viability of the format is seriously threatened. Its major threat appears to be the emergence of competing formats (Academy Advancing High Performance Audio and Video 1998). In particular, the digital video disk (also known as the digital versatile disk or DVD) poses a serious challenge to analog LD. DVDs' perceived advantages include lower production and distribution costs, higher-quality video and sound (see table 1), playback capability in computer DVD-ROM drives, more overall storage capacity, and more levels of interactivity (Messier 1998). At the consumer level, the DVD format can be recordable and rewritable, distinctly unlike the laborious and expensive mastering process required for producing laser discs. The laser disc market, which peaked in 1994 with $345 million in sales, suffered a 20% reduction in revenue upon DVDs' first availability in the marketplace in 1996 (Brass 1998).

The Tiananmen Square installation uses Pioneer LD-V2000 laser disc players. The LD-V2000 was a new model in 1989 and is no longer manufactured. Pioneer Electronics, the holder of numerous key LD patents, is still one of the only major suppliers of LD hardware. At this writing, the company still manufactures LD players, but the forecast for ongoing support is unclear at best. An article recently removed from Pioneer's own website (which purports to refute the death of the format) says that the format should be viable for “three to four years”and recommends transitioning to DVD using Pioneer's line of laser disc–DVD hybrid players (Wujcik 1996). In 1998 Pioneer President Kaneo Ito said it was his belief that “Laser disk will cease to be viable in no more than approximately 1 to 11/2 years” and that the manufacture of combination laser disc–DVD players could cease at that time. The Imation Corporation is possibly the only remaining vendor in the United States offering laser disc mastering.

4.3 PRESERVATION OUTLOOK FOR THE MASTER VIDEOTAPES

As mentioned in section 2.1, Birnbaum made the original off-air recordings using 3/4 in. U-matic videotape. The video was transferred to Betacam SP for editing. Birnbaum retains the original 3/4 in. U-matic tapes and the Betacam SP “disc masters. ”The owners of the two editioned copies have Betacam SP submasters.

Table .

A Comparison of Some Common NTSC Video Formats

U-matic is a composite videotape format introduced in 1971. The format has a very large installed base of professional users, such as news-gathering organizations. It is the first successful videocassette format. Major industry backers of the format included Sony, JVC, and Panasonic. Betacam SP is an analog component format introduced by Sony in 1986 on the heels of the demise of its Betamax format. Another format aimed at professional video applications, Betacam SP is popular among news-gathering agencies for field acquisition and postproduction.

Like laser disc, both U-matic and Betacam SP are “threatened” formats. Sarah Stauderman, in her Video Format Identification Guide(Stauderman and Messier 1999), defines threatened formats as follows: “The playback machines are available; however, either the tape format itself is unstable or has less integrity than other available formats, or it is known that a more popular or updated format will be replacing this one in a short period of time. ” The advent of newer digital formats, especially those targeting news-gathering organizations and other professionals engaged in field acquisition of video, are rapidly displacing U-matic and Betacam SP, as playback hardware for these formats becomes increasingly scarce.

Impending format obsolescence is only part of the problem, as magnetic tape is an inherently unstable medium with a life expectancy of only 10–30 years, given proper handling, minimal playback, and storage at relatively dry and cool conditions of 68oF and 40% RH (Van Bogart 1995). The stability problems of magnetic tape have been examined in depth and are commonly attributed to hydrolysis of the binder medium used to affix the metallic pigments to the tape substrate (Van Bogart 1996). The stability problems facing magnetic tape are not merely theoretical or hypothetical: a recent conservation survey of a media center's video holdings revealed that 20% of the 3/4 in. U-matic tapes in the collection do not play back due to the chemical and physical break-down of the tape (Messier 1997).

4.4 LCD MONITORS

The installation originally used four Sony FDM-330 liquid crystal display monitors known as “Watch-man. ” These monitors had a screen size of 2.7 in. (measured diagonally) and were capable of displaying video input to the NTSC standard of 30 frames per second with a horizontal resolution of 320 lines. While the name “Watchman” persists, Sony has not manufactured these particular monitors for close to 10 years. Attempts to obtain technical specifications on the product from Sony for this report were fruitless. Despite an apparent willingness to help, Sony technical personnel do not have ready access to information on products the company no longer manufactures.

The Sony monitors were used in the early exhibitions of Tiananmen Square: Break-In Transmission at the Josh Baer Gallery (1990) and Rhona Hoffman Gallery (1991). The FDM-330s were obsolete by the time of the next exhibition at Boston's Institute of Contemporary Art (December 1992). This exhibition used another model LCD display, most likely manufactured by Panasonic. As mentioned in section 2.3, the SFMOMA's Seeing Time exhibition replicated the piece. According to Matt Biederman and Steven Dye of the SFMOMA installation staff, finding LCD monitors that matched the original FDM-330s proved impossible. Working with Birnbaum, Bieder-man and Dye finally settled on monitors manufactured by the Citizen Corporation (Biederman and Dye 2001).

Specific models of LCD monitors are driven into rapid obsolescence owing to the recent pace of technological and manufacturing innovation. This situation has been especially true in the last 10 years as the demand for flat screen displays for portable computers has increased dramatically. The current swift rate of development belies the fact that LCD technology is not especially new. LCDs are grounded in principles first described in the late 19th century. This early experimentation showed that the crystalline structure of certain materials can be precisely altered through small changes of temperature, pressure, and current and that these changes are fully reversible when the influence of the variable is removed.

In 1963, the RCA Corporation was the first to exploit this principle to display information, using an applied voltage to alter the refractive index of liquid crystals, thus altering the light-scattering and transmission properties of the material. RCA used applied voltage to alter the orientation of linear crystals along their axis, effectively causing the crystal to twist. These socalled twisted nematic (TN) displays alter the transmission or reflection of polarized light, depending on the crystal orientation. TN displays are made by arranging these linear crystals in a grid controlled by horizontal and vertical bands of electrodes. Independently addressable picture elements, known as pixels, are formed at points of overlap between the horizontal and vertical bands of electrodes. There are substantial limitations in this method, since addressing individual pixels in the matrix requires voltage to be applied to an entire row and column of electrodes. This addressing method is known as “passive matrix. ” Passive matrix TN displays are typically used for low-information-density, monochromatic displays such as watches and calculators. In 1973, the Westinghouse Electric Corporation created the first active matrix display in which individual pixels could be uniquely addressed through localized voltage changes without engaging the other pixels in the matrix. This more-refined level of control is based upon associating a thin film transistor (TFT) with each pixel. While TFT displays are still based on the inherently monochromatic twisted nematic method for selectively blocking transmitted light, color is achieved though dividing each pixel into thirds and applying red, green, and blue filters. Active-matrix TFT displays are used in applications requiring high information density and rapid changes, such as portable computers, camcorders, and digital cameras. The original Sony LCD monitors used in Tiananmen Square: Break-In Transmission were most likely active-matrix TFT displays. The disadvantage in active-matrix TFT displays is the high manufacturing cost inherent in associating a single transistor with an individual pixel. Introduced a decade after the TFT, supertwist nematic (STN) displays rely on the simpler and easier to manufacture passive matrix method. STN displays use liquid crystals that have a dramatically enhanced twist response as compared with earlier TN displays. This higher level of response correlates to higher levels of contrast as transmitted light is more effectively transmitted or blocked. As with TFT, color in STN displays is achieved through the use of the additive color filters. Compared to TFT, STN typically has slower response time, though innovations in the early 1990s allow STN screens to be used effectively for the display of video.

While LCD technology is significantly advanced, it is by no means a “mature” technology, as new applications, increasing demand, better manufacturing methods, and competing display systems influence its development. The pace of development and the resulting cycles of obsolescence are reflected in the Birnbaum piece where the LCD monitors have changed three time in the past 10 years.

For Tiananmen Square: Break-In Transmission these changes have not meant progress. Birnbaum believes that the original Sony monitors were superior to later replacement models in terms of clarity and brightness. Not only was the quality better but Birnbaum was also attracted to the term “Watchman” for its talismanic appeal (Birnbaum 2000b). Unfortunately, such miniature LCD monitors are mostly relegated to the lower end of the consumer market. Consequently, the significant strides in the technology that are readily integrated into highend consumer devices have very little impact on cheaper, smaller, commodity-item LCDs. At this point, there is very little choice when it comes to selecting replacement LCD monitors that fit the design and size requirements of the installation.

4.5 CRT MONITOR

The original cathode ray tube color monitor used in the installation is the NEC PMC 2571-A. The original monitors are still in use in both editions of the installation. NEC has not made this monitor in almost 10 years. The PMC 2571-A was marketed as a professional video monitor, with high-end features that included an 8-pin connection for direct connections to 3/4 in. U-matic VCRs, specialized filters to enhance the sharpness of composite video, a pass-through connection for the video signal, and a built-in stereo amplifier, integrated stereo speakers, and left and right audio output. The monitor has 400 lines of horizontal and vertical resolution, which, according the original NEC specifications, is 30% better than conventional television monitors. The dimensions of the monitor are 231/4 in. vertically, 253/16 in. horizontally, with a depth of 201/2 inches. The diagonal screen measurement is 25 in. The monitor weighs 87 lbs.

Unlike the situation with LCDs, CRT technology is “mature. ” Since the 1960s, the installed base and manufacturing capacity for CRT televisions and computer monitors has been huge and growing at a constant rate. Only recently has the dominance of CRTs been challenged as LCDs are gradually being used in high-end computer systems and television. LCD, plasma, and other flat panel display technologies are making rapid strides and can be expected to significantly displace CRTs for most applications by the end of the decade. However, the high price of these alternatives ensures that quality CRTs (like the PMC 2571-A) will be available in the near term.

4.6 SEQUENTIAL SWITCHER

A sequential switcher is an electronic component that is connected to multiple video sources such as cameras, VCRs, or, in the case of Tiananmen Square: Break-In Transmission, laser disc players. The switcher outputs only one signal at a time, working through the multiple input signals at a predetermined interval and sequence. For Tiananmen Square: Break-In Transmission, the four video signals from the LD players are sampled by the sequential switcher and output for durations of 7–12 seconds for display on the CRT monitor.

For the most part, sequential switchers are integrated into security systems, where the output of multiple cameras is periodically displayed on a single monitor located within a centralized guard station or recorded by a videotape recorder. Sequential switchers can also integrate audio switching, though this feature is not standard and adds to the cost. Since the CRT station in Tiananmen Square: Break-In Transmission does not have sound, this feature is unnecessary.

Initially, Tiananmen Square: Break-In Transmission used the Panasonic WJ-525 sequential switcher. The video input on this device allows for connection to up to 14 composite video input sources, using BNC connections. The switching interval is adjustable between 1 and 30 seconds. The device measures 13/4 in. high, 187/8 in. wide, and 97/16 in. deep. It weighs 6.8 lbs. The WJ-525 was first brought to market in 1981 and is no longer manufactured by Panasonic. Presently, similar devices with nearly identical functionality are readily available.

4.7 LOUDSPEAKERS

The eight speakers used in the installation are Teledyne Acoustic Research Powered Partners loud-speakers, model AR-570. The loudspeakers are “powered,” meaning they integrate an amplifier (necessary since the audio signal from the laser disc players is not amplified), delivering 30 watts of power. As such, the speakers require AC power, though they can be adapted for use with 9–25 volts of DC power. The loudspeakers are capable of delivering approximately 109 dB sound pressure levels at 1m, relatively powerful for their small size. The signal to noise ratio is 85dB. Woofer diameter is 4 in., tweeter diameter is 1 in. The speakers are triangular, with the back of the speakers at the apex and the front forming the base. They are 61/8 in. high by 101/2 in. across the face and 75/8 in. deep. Each speaker weighs 8 lbs. The speakers have rotary volume and bass and treble controls. They connect to the laser disc left and right audio out jacks using standard RCA connectors.

Acoustic Research is no longer affiliated with Teledyne and is now a subsidiary of the Recoton Corporation. Recoton owns other audio component companies, including Advent and Jensen. At some point, the Powered Partners line of loudspeakers shifted from Acoustic Research to Advent, and, until very recently, Advent manufactured the loudspeakers as the AV-570. At present it appears the loudspeakers are no longer being manufactured, though they are still available through retailers. While the future of the AV-570 is unclear, quality amplifier-integrated loud-speakers (some accepting both digital and analog signals) are widely available for use with personal computers. Such speakers, however, are unlikely to have the same triangular appearance and overall dimensions as the AV-570.