Michael Graves

This author has written 1376 articles

IETF CODEC News: OPUS Is Ready For Testing

On the mailing list of the IETF’s CODEC working group Jean-Marc Valin made a significant announcement on Feb 4th. It reads as follows:

Hi everyone,

We’d like to announce that the Opus codec is now ready for testing. The bit-stream is now is a “pseudo-freeze”, which means that unless a problem is found during testing/review, there are no longer any changes planned. The only exception to this are the SILK-mode FEC and the stereo SILK mode, which should be landing in the next few days. Considering that these are not critical features, we felt like the testing phase could already begin.

<snip>

Cheers,

Jean-Marc

Please recall that OPUS is the new codec arising from the combination of CELT and Skype’s SILK. It’s multiple operating modes accommodate many different applications, from extremely low-latency high-quality links between production studios, to voice applications on very low bit-rate channels. OPUS brings us the current state-of-the-art in audio codec technology in a royalty-free, open source form.

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Advantage GSM Carriers: Simultaneous Voice & Data

Now that Verizon Wireless is getting traction with the iPhone 4 on their CDMA network AT&T is left trying to find ways of differentiating itself. While it’s too early to know how much of a bloodletting AT&T will suffer, it’s clear that in many parts of the country Verizon’s much touted network supremacy will win over a significant number of frustrated AT&T customers, even if it means buying a new CDMA capable iPhone4.

Perhaps the biggest difference between the two carriers is the type of networks they operate. Networks based upon GSM standards, like AT&T and T-Mobile here in the US, allow the simultaneous use of voice and data. In marked contrast, CDMA networks like Verizon’s, simply don’t do this.

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Deep Geek: Audio Beam-Forming In The Real World

Have you ever encountered something that seems a little odd, then find that you are in fact surrounded by examples if it in your daily life. So it is with “Beam Forming.” You may never have heard of it, but it’s all around you, and it’s more than a little interesting.

Wikipedia tells use that, “Beam forming is a signal processing technique used in sensor arrays for directional signal transmission or reception.” It is essentially a way of using an array of omnidirectional sensors to synthesize directionality.

Cast into the audio domain beam forming is a way to use the signals from multiple omnidirectional microphones to create the equivalent of a direction microphone. Further, since the process is based upon signal processing, it can be variable. It can create the equivalent of an electronically steerable microphone, complete with the ability to “zoom” in or out. It’s not unlike a zoom lens for sound.

Sounds cool, right?

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