Indeed, with separate pavilions devoted to home networking, RF and wireless applications, and an entire exhibition center devoted to multimedia — with or without the PC — the show once called the Computer Dealer's Expo, Comdex may increasingly have less to do with the market for personal computers.

The crop of audio news from Comdex last week revealed an industry shifting its focus away from the PC to a mix of broader applications.

Audio chip maker Cirrus Logic Inc. (Austin Texas) announced a licensing agreement with LuxSonor Semiconductors Inc. (Fremont, Calif.) that will enable Cirrus to integrate and manufacture MPEG-2 video playback devices. The agreement is intended to enhance the company's position among manufacturers of DVD players by allowing Cirrus to provide them with both audio and video decoder chips.

The MPEG-2 capability intentionally complements Cirrus' share of the Dolby Digital decoder market among manufacturers of the high-end AV receivers used in home theater systems — already greater than 50 percent in a market that is expected to grow to 28.8 million units in 2004, according to Forward Concept.

Cirrus also used Comdex to reinforce its position in PC audio — a position every bit as enviable as Creative Laboratories. It promoted the CS4205 AC-97 codec, a device intended to reduce some of the cost complexity associated with docking functions in portable computers, said Brain Straup, director of systems engineering and chief architect of the part.

The device is "digital-centric," he said. It integrates a Zoom Video port (providing a digital signal path for signals coming from MPEG decoders), a digital mixer, digital tone controls, and an I2S serial I/O link. It also includes SRS Lab's 3-D sound processing algorithm, which broadens the sound stage produced by two speakers.

Meanwhile, Cirrus competitor SigmaTel Inc., also based in Austin, went the opposite direction by demonstrating devices that showed greater linkage to the PC environment. Its Dolby Digital audio decoder, for example, relies on Pentium hosts to perform much of the work of AC-3 algorithm processing. That is, the host would perform much of the work of segregating 5.1 audio channels (left front, right front, center, left rear, right rear, and bass subwoofer) from a single 192-kbit/second data stream.

SigmaTel's Comdex demonstrations, like the Dolby Digital decoder, was a promotion in behalf of "soft audio," in which the host processor performs most of the audio decode and equalization functions, dramatically lowering the cost and space required to implement playback, said Alan Hansford, SigmaTel's vice president of marketing. A bare-bones Dolby AC-3 soft decoder chip set could offer a 103 dB signal-to-noise ratio, for about $1.50, he said.

Soft AC-3 needs 233 MHz, said Hansford. The power of new-generation Pentium processors is an obvious enabler for simpler audio/video playback silicon. "You can run a movie on the Internet through a DSL connection; you can decode both audio and video with a 500-MHz host," he said.

SigmaTel, whose AC-97 codec sales now challenge Cirrus' according to market analysts like Mercury Research, also demonstrated its STMP34XX MP3 player chips.

Its MP3 player includes a flexible memory interface, a DSP and USB interface for connection with a PC host. It includes an 18-bit sigma-delta codec, an FM radio interface, an LCD driver, headphone output and microphone input. The intent is to replace about $24-worth of electronics with a $15 part, enabling MP3 players in the $79 to $250 price range. All the features are available with one device; the player manufacturer just needs to enable them for the kind of player he is building, said Hansford.

Apogee Technology Inc. (Norwood, Mass.) parked itself in the multimedia center at the Sands Expo Center and demonstrated digital amplifier technology that could live either inside or outside the PC environment. Apogee's "all digital" solution is effectively a two-chip class D amplifier that could convert a serial digital audio data stream into two analog channels, each driving 35 watts into 8-ohm speaker loads.

While Apogee showed the EB-2060X reference design that could easily fit on a PCI card, it also displayed DVD consoles whose outputs could be routed directly to speakers. The evaluation board for the DDX-2000/2060 chip set will easily fit inside DVD players, giving console makers the option to integrate all parts of the audio signal processing chain, said David Meyers, Apogee's director of business development.

The Direct Digital Amplification (DDX) technology promoted by Apogee converts a serial digital audio data stream into a pulse-width modulated stream.

The output of the PWM is effectively a three-state waveform, consisting of a positive-going pulse, a negative-going pulse and third state, which is momentary grounding of the output.

This momentary grounding — which Apogee calls DDX Damped Ternary — is similar to what switching power supply manufacturers Vicor refers to as "zero crossing." It elevates the efficiency of the amplifier, said Meyers.

Texas Instruments Inc. has deployed a similar technology for Class D amplifiers in which the pulses are phase shifted slightly at the zero crossing point.

Chip set demo

Neoh Chong Lim, managing director of FreeSystems Pte. (Singapore), one of the principals in Tritech Microelectronics — a company that was driven out of business by patent infringement suits from Cirrus Logic — demonstrated the Freespan digital wireless chip set.

As implemented in a high-fidelity wireless headset, the transmitter device converts an audio stream (in I2S format) into a Sony-Philips Digital InterFace (SPDIF) format that is transmitted at 2 MHz through an infrared output.

While the wireless headphones of xdream depend on line-of-sight infrared to transmit audio in a digital format, the system has a wider bandwidth than typical wireless headphones using FM wireless transmission, and there is no hiss in the perceived signal. The frequency response of the set is 20 Hz to 20 kHz, with an SNR better than 90 dB at 1 kHz.

The xdream wireless set consists of two pieces: a battery-powered headset with an on-off switch and volume control, and a transmitter that is attached to a host.

The use of both USB and RCA audio jacks on the transmitter means that the audio headphone can be used with PCs or as a standalone with some other audio playback system.