Blink Does Opus

Last week there was some exciting news on the AG Projects mailing list; Blink support for the Opus codec was being released for the Mac version of Blink. A similarly capable release of the Windows version was expected shortly. Earlier this week Adrian Georgescu, the A. G. of AG Projects, passed me a Blink for Windows release candidate for experimental use.

This beta release installed readily, right along side the production release. I quickly registered it with my account at SIP2SIP.INFO so that we could have a couple of brief test calls.

Since most telephony oriented audio hardware doesn’t do justice to full-bandwidth audio I connected my Blue Microphones Yeti USB Microphone and a pair of AKG K 240 Semi-Open Studio Headphones . It seems that the team at AG Projects have also settled on the Yeti as a very good, yet affordable choice for high-quality sound pickup.

Adrian and I conducted a short series of test calls. He first called using G.711 simply to confirm connectivity and the baseline behavior of the echo cancellation routine. We then repeated that exercise using G.722, which sounded much better, as you might expect.

In a third test call we enabled Opus but with a 32 KHz sample rate. Certain aspects of Blink, including the echo cancellation, voice activity detection and background noise suppression, are designed for use with 32 KHz sampling. This combination of settings allows for use of Opus along with all of the voice-related conveniences. As a practical matter that means not being forced to wear a headset.

Speaking with Adrian over Opus at 32 KHz sounded notably better than G.722. The difference, while real, is not especially compelling for voice alone. Its value becomes more apparent when music is involved. Adrian made this point by turning on a good quality stereo as we were speaking.

With the music turned up to a considerable level, and use a Yeti himself, the music was well reproduced at my end of the call. It’s worth remembering that FM radio rolls off beyond 15 KHz, which is about what we experienced with Opus in this mode.

Those who wish to have very best possible audio experience can disable the echo cancellation routine and select the 48 KHz sample rate. That implies that you will need to use a headset. In my case the Yeti + AKG combination takes adequate care of that.

It’s worth noting that the sample rate setting internal to Blink can be switched between various rates, including; 8 KHz, 16 KHz, 32 KHz, 44.1 KHz and 48 KHz. If The Opus codec is in-use the call status will always be reported as 48 KHz.

Over the next short while I hope to make a couple of test calls between two instances of Blink, measuring the resulting audio channel. I’m confident that it will more than meet the requirements of podcasters like Mike Phillips who might be seeking an alternative to Skype.

This new release of of Blink for Windows remains in beta, but was just made available here.