Electronic Design

PC-Hosted Audio Accelerator Delivers 5.1-Channel Sound

Delivering a full 5.1-channel sound capability, the Thunderbird Avenger audio accelerator chip brings the home-theater experience to the PC. Its multichannel sound output totally immerses users in simulations, games, movies, or any other PC application. This chip also is the only accelerator that combines multichannel speaker support, hardware acceleration, and two-speaker 3D virtualization. It's designed for use on either a PCI adapter card or on the motherboard.

A dedicated, programmable digital-signal-processing controller that performs most of the audio data-stream processing is included on the chip. A 3D virtualizer that takes the AC-2 multichannel signal and encodes it into two-channel virtualized 3D audio also is on board. Employing the algorithms developed by QSound Labs, the chip eliminates the need for cross-talk cancellation. Moreover, it delivers a wide "sweet-spot" for strong positional perception.

With only two speakers, users can enjoy a true 3D experience regardless of head movement and positioning. An S/PDIF (Sony/Philips digital interface) output that can feed the AC-3 data stream to an AC-3 decoder is included on the chip as well. This output lets a wide variety of consumer audio systems be connected to the PC, such as stereo receivers, minidisc players, or digital speakers.

The chip's audio performance is similar to the previously released Thunderbird accelerator. The new version can handle up to 96 simultaneous 3D streams. It also can support 256 DirectSound streams and up to 320 wavetable voices. In addition, it manages MIDI music synthesis and includes an integrated game port for analog or digital joysticks.

Both of the models offer virtualized three-dimensional output, along with the lowest overall overhead requirement from the host processor of any mainstream audio accelerator chip. Among the features included are support for 16-channel virtual write master for stream redirection, and special-effects capabilities such as reverb, occlusions, and obstruction to provide positional queues.

Broad API support is available for the Thunderbird Avenger chip (the SAA7785), including DS3D, EAX 1.0, EAX 2.0, I3D Level 2, and A3D 1.0. Samples are immediately available. In lots of 10,000 or greater, the chip sells for $12.45 apiece. Production quantities will be available later this quarter. The previously released Thunderbird chip, the SAA7780, sells for $9.60 apiece in similar quantities.

Philips Semiconductors, 811 E. Arques Ave., P.O. Box 3409, Sunnyvale, CA 94088-3409; Greg McCarthy, (480) 752-6372; www.semiconductors.philips. com.

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