Cable Tech

Broadcom Chips Away at Voice

Chanting its usual mantra of integration -- the combining of multiple chips into a single device -- Broadcom Corp. (Nasdaq: BRCM) announced today what it claims is the first single-chip voice processing unit, targeted at set-top boxes, cable modems, and DSL modems.

The company's BroadVoice product is based on the BCM3341 chip, which has at its core a digital signal processor (DSP), the central engine for any voice-processing chip or box. But the chip also includes many of the required peripheral chips, such as those that provide POTS (plain old telephone service) ring voltage or keep watch on the power level of a modem's backup battery.

Broadcom appears to be the first company to integrate that many telephony devices onto one chip, says Will Strauss, president of research firm Forward Concepts Co. "Texas Instruments Inc. probably comes closest, but not specifically for the cable market."

Broadcom also put serious work into its codec, the compression/decompression algorithm that runs on the DSP, digitizing the voice signal and shrinking the amount of bandwidth it uses. The International Telecommunication Union (ITU) has established two standards for voice codecs, the commonly used G.729 and the higher-end, more expensive G.728. Broadcom makes chips for both these codec standards, but company officials felt they weren't ideal for broadband.

"They're complex and they're big, and in a consumer world they're not the best solution," says John Gleiter, Broadcom's director of marketing for cable modems.

Broadcom hired a team that included Bell Labs researchers experienced in G.728/729 codecs, charging them with developing proprietary codecs that run on the BCM3341.

Of course, this opens up the usual issues with interoperability. "It does no good to use 'G.Broadcom' if the guy on the other end doesn't know what G.Broadcom is," Strauss says.

In fact, Broadcom is shooting to use its own codec on isolated networks where proprietary systems might be used. One version of the BroadVoice codec supports wideband telephony, which provides CD-quality signals without that static-filled, "filtered" telephone sound -- but only if both parties are using wideband-enabled phones.

Broadcom sees some advantages in developing its own codecs. They do a better job than those already supporting the standards, Gleiter says, and they avoid the royalties tied to G.728/729.

At the Western Show this week, Broadcom is demonstrating its new chip, running inside a gateway by Cedar Point Communications Inc. The BroadVoice chip and codecs are shipping in volume.

— Craig Matsumoto, Senior Editor, Light Reading
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