[April 19, 2001]

Commextrex Releases High Density G.726 Vocoder

Commetrex Corporation announced it had achieved one of the communications industry's highest density G.726 vocoders. G.726, long used in switched-circuit trunking applications, is finding a new home in packet voice due to its high voice quality, low algorithmic delay, and low MIPS requirements.

G.726 -- which compresses 64 Kbps voice to 40 Kbps, 32 Kbps, 24 Kbps, or 16 Kbps -- typically consumes 5 MIPS on a Texas Instruments (TI) TMS320C5400 DSP, yielding 20 channels on a single part. Commetrex claims a 50 percent improvement. TI reports 125 channels on its 300-MHz TMS320C6203 DSP. Commetrex offers 190 channels.

Cliff Schornak, Commetrex' CTO, explained: "The TI TMS320DSPC6000 has two sets of four parallel execution units, so we knew we could process two samples per cycle. But, the ADPCM algorithm of G.726 does not lend itself well to keeping all those execution units busy. So we were very pleased when we saw that our implementation had 6 of the 8 units busy most of the time, explaining how we were able to get down to 1.55 mega-cycles per sample."

Steve Rudner, Commetrex' VP, Sales, said: "I am pleased to be able to offer this highly efficient implementation as licensed technology. It is available in an eXpressDSP Algorithm Interface Standard-compliant version, in an MSP Consortium M.100-compliant version, and on our MSP Media Gateway DSP boards."

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