Ask Uncle Willy #3: July 7, 1995
Uncle Willy has received several questions about the sounds and music in games by Williams Electronics Games, Inc. Since this a rather extensive subject, Uncle Willy has decided to devote this week's issue of Ask Uncle Willy to covering this subject in depth. Uncle Willy apologizes for the length of this article, but hopes this topic proves interesting.
All comments and questions are welcome. Keep in mind that some questions just do not have an answer. Others, of a proprietary nature, do not permit an answer.
Uncle Willy enjoys hearing from you!
Question: Can you tell me about the sounds and music from the games by Williams Electronics Games, Inc.? How are the sounds made? How is the music composed? How does the sound system recreate sounds? Who are the people who compose music for Williams games? Answer: Introduction Williams Electronics Games, Inc. designs and manufactures pinball games under the Williams and Bally names and coin-op video games under the Midway name. Anyone who has played these games knows that the computing power and graphics behind them have become very sophisticated and lifelike. Pinball games are equally sophisticated, often containing several computer-controlled playfield toys that are integrated into the pinball action. To keep the audio on par with these state-of-the-art games, Williams has developed a new sound system, called DCS (which stands for Digital Compression System). The DCS sound board provides four channels of 16-bit digital audio, with independent control over the volume, looping and playback of each channel. Each channel can dynamically play back anything from an entire piece of music to a short sound effect, with a typical game using one channel for music and the remaining three for sound effects, speech and foreground music such as fanfares or breaks. The first pinball game to use DCS was Indiana Jones. The first video game to use DCS was Mortal Kombat II. Background DCS is not the first digital game sound system, but it is the first truly high-fidelity, digital audio system designed specifically for coin-op arcade pinball and video games. A comparison to past and current game sound systems puts its sophistication and sound quality in perspective. The "beeps" and "blips" of early arcade games were made with analog circuits and simple digital tone generators. These sounds dis- appeared from arcades in the early 1980's when chip sets became available to do FM synthesis. For several years, most sound systems for arcade games combined a microprocessor, and FM synthesis chip set, and a low sample rate, low quality digitizing system. These systems were very similar to many of the sound cards currently available for personal computers, and provided fairly complex music, somewhat understandable speech and sonically interesting (if not altogether realistic) sound effects. FM synthesis was in turn replaced by sample playback systems, implemented with custom hardware or with software running on a Digital Signal Processor (DSP). Samples help to make music more realistic, but the systems often suffer from a lack of polyphony and and upper limit of a few seconds recording time for each sample. One of the most recent advances in game sound is CD-ROM. Although CD-ROM technology is popular in home and personal computer games, there are several drawbacks that limit its usefulness in fast-paced, multi-player arcade games. One problem is that CD-ROM audio schemes are limited to a single channel of mono or stereo sound. Arcade games require several independent sound channels for layering music, sound effects and speech. Access time is another problem. Delays as short as 20 milliseconds between action and sound can make an arcade seem sluggish. Most of the CD-ROM game systems rely on a separate sample playback or FM synthesis system for interactive sound effects. Also, few CD-ROM systems can withstand the bumping and shaking excited players can inflict on arcade game cabinets. DCS was designed to overcome the limitations of other game sound systems. There were three main design parameters: improving sound quality, maintaining interactivity and streamlining sound develop- ment. 16-bit audio played back at 32 kHz delivers near-CD sound quality. The ability to instantly start, stop, loop and control the volume of four independent channels in response to commands from the game provides interactivity. Most importantly, the process of developing sounds changes from programming synthesized sounds to producing music and sound effects in profession recording studios. Audio Data Compression The biggest limitation with most game and multimedia sound systems is storage. 16-bit digital audio at a rate of 31,250 samples per second requires about 60 kilobytes of storage per second of sampled sound. Overall cost of a game limits the ROM available for sounds to about 3 megabytes. The problem is that 3 megabytes of ROM at 60 kilobytes a second is only enough for about one minute of total sound. Most Williams games have a total of 10-15 minutes of non-repeating sound. The solution to this storage problem for DCS was the development of a proprietary transform coder algorithm that reduces a 500 kilobit/ second data rate by a factor of ten or more, and runs on a low cost DSP chip. This algorithm is similar to the algorithms used in the Sony MiniDisc format, the Philips Digital Compact Cassette format and the emerging digital sound formats for movies such as Dolby Stereo Digital, Sony Dynamic Digital Sound, and Digital Theater Sound. The encoding phase takes place on a PC, starting with digital audio files. The fields are broken down into frames of 240 samples each. A frame is 7.68 milliseconds of audio, and files can range from one to several thousand frames in length. Each frame is transformed by a 256-point Fast Fourier Transform, with simple cosine windowing and eight samples of overlap on each end. The resulting spectrum is further broken down into 16 bands and quantized according to masking curves and user-controlled parameters. The quantizing levels and the resulting data for each frame are entropy encoded into variable length packets. The packets for each file are combined with header blocks and stored as files that are used later to generate ROM images. The decompression phase takes place on the DSP chip. Starting with the header, a packet of compressed data is read from ROM and decompressed into a frame. This involves entropy decoding the data stream, and then de-quantizing the data into a frame of frequency domain data. The four channels are decompressed independently and summed in the frequency domain. Volume operations, such as level settings and cross-fades, are also performed in the frequency domain. The final frame is inverse transformed and clocked out a serial to a Digital to Analog Converter (DAC). Music and sound effects compress to an average of 50 to 70 kilobits/second, and speech reduces to 20 to 40 kilobits/second. The resulting audio quality exceeds that of other algorithms operating at similar bitrates. Several aspects of the DCS algorithm capitalize on the nature of sounds for games. The encoding, which is more complicated than decoding, can be performed on a PC without any restrictions on processing time. The algorithm has a variable bitrate, which means that the amount of artifacts and the overall quality can be fine tuned for each individual sound. Since the frame size is small, it is possible to carefully edit sound effects and seamlessly loop music. Hardware The DCS hardware is relatively simple. The major components, a surface-mounted DSP chip, sockets for ROM, a 16-bit mono DAC, and an audio power amplifier, are contained on a two-layer printed circuit board measuring about eight inches square. There are additional discrete analog and digital components making up filter, interface and power supply circuits. The DSP chip used is the ADSP-2105 by Analog Devices. The 2105 runs at 40 MHz and executes over 10 million instructions per second. The 2105's on-chip RAM is supplemented with additional static RAM on the DCS board. This memory is used primarily as temporary storage for the realtime decompression and inverse FFT operations required for each of the four playback channels. DCS contains a bi-directional, 8-bit interface between the sound board and the game host. Playback commands from the game host can trigger anything from a single sound effect to a one-minute segment of music that loops indefinitely. Commands from the host are asynchronously received and buffered and can arrive at a rate greater than 25 thousand per second, although a typical rate in game play is 10-100 per second. The sound board can also send timed data back to the game host. This data is useful for synchronizing animation, display effects and light shows with music and sound effects. Staff Several full time composers and one freelance composer produce sound effects, voice overs and music for all of the pinball and video game projects. Jon Hey has been at Williams for several years. The Jon Hey Band recently headlined at the Chicago Film Makers benefit and performed at the Bucktown Arts Festival in Chicago. Vince Pontarelli joined Williams two years ago, having previously worked at Libman Music, a well-known Chicago jingle and post-score house, and as a writer for Todd Scales at Windsound. Dave Zabriskie also joined Williams fairly recently, having come from Premier pinball. In addition to a long list of game sound credits, Dave has written extensively for orchestral and choral groups, including a recent string symphony for the Chicago String Ensemble. Kevin Quinn is the newest addition to the Williams sound department. Before coming to Williams, Kevin owned and operated Concord Music, a successful commercial jingle house in Chicago. Freelancer Dan Forden works out of his own project studio. Dan has put together and worked out of several project studios over the last several years in connection with bands that he has both played in and recorded. Facilities Each staff composer has an office and a MIDI workstation. Supporting the MIDI workstations is a fully equipped recording studio built around a Tascam M-2516 16-channel mixer. Four patch bays connect the mixer to a DS-30 DAT recorder, a CD player, an Alesis ADAT and the outboard gear, which includes a Lexicon LXP-15, an Ensoniq DP/4, and various equalizers and compressors. The studio is divided into two rooms, one of which is built around an isolation booth. The studio is used mostly for recording vocals and voice-overs in the isolation booth and for creating and editing sound effects on a Macintosh IIci running Digidesign Sound Tools. Sound files are stored on removable 45 megabyte cartridges, making it easy for each person to manage the files for the game projects he is working on. Production Original music is composed for each game. The MIDI workstations for the staff composers consists of a Mac Quadra 630 running Mark the Unicorn Performer software, a Kurzweil K2000 keyboard, one or more Emu Proteus modules, Roland JV 1080 sound modules, and Ensoniq DP/4 effects processor, and Alesis Quadraverb II, and Alesis Quadraverb GT and an Alesis D4 drum module. Each workstation also has its own MIDI interface, mixer, compressor and equalizer. For variety, there is also a Roland JD-990, a Korg 01W/FD, and Ensoniq SQR and two Akai S1100 samplers and an Alesis ADAT digital multi-track tape machine. In addition to the Mac Quadra, each composer also has a '486 or Pentium PC. The PCs are used for hard disk recording and editing, using custom hardware and software that generates files for the data compression system. All music must be uniquely arranged and recorded for a game, even when the music is based on a film or television score. For example, in Star Trek the Next Generation pinball, which was arranged and scored by Dan Forden, the music package included an arrangement of the show's well known theme (based on the movie theme by Jerry Goldsmith) as well as several original Forden compositions. Sound effects for games fall into three basic categories: sound effects pulled from CD, field recordings and sounds taken from film or video soundtracks. Williams owns several sound effects libraries. A portable DAT recorder is used to make field recordings. Many sounds, such as those used in the Indiana Jones pinball, are taken from sound effects submixes of film soundtracks. Regardless of the source, almost every sound effect is custom edited and processed to work in the context of the game. Speech and voice effects are also an important part of the sound package for any game. Anywhere from a fourth to a third of the available memory space is used for speech and voice effects which inform and entertain the player. This is especially important in games based on movies or other high profile themes. For example, each major cast member of the television series Star Trek the Next Generation recorded material expressly for the pinball game. Vocal talent is also recorded in the isolation booth located in the Williams sound department studio. This was the case with all of the screams, grunts and moans heard in the Mortal Kombat II and 3 video games. Because WIlliams sound designers now work in a recording studio using professional tools, as opposed to programming music and sounds in assembly language, the time to complete a sound package for arcade pinball and video games has been cut roughly in half. More import- antly, the sound quality has been drastically improved with the advent of DCS.
All text and images Copyright © 2005 The Pinball Factory. All games made under license to Williams Electronic Games Inc.