Next week the IETF will be holding a conference in Berlin. Part of that conference is a Technical Plenary Session about the Opus audio codec scheduled for Monday, July 29th 5:40-7:40pm CET. The IETF usually streams much of their conferences…
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.
Think back to the handful of new audio codecs that have been released over the past few years; CELT, SILK and Opus to name a few. Then there are the handful of proprietary codecs that have become available under more attractive licenses. Polycom’s Siren family come to mind on that front. In all of these cases I have observed that the Freeswitch development team are typically amongst the very first to implement any new codec.
In recent weeks they have added support for G.719, an ITU standard codec created by Polycom and Ericsson. With a sample rate of 48 KHz, G.719 is a full-bandwidth codec, supporting a useful audio channel of 20 Hz- 20 KHz. It does so with end-to-end delay of only 40 ms and at bit rates from 32 kbps to 128 kbps. It also supports stereo audio.
Upon completion of the ITU standards process Polycom published a white paper on the codec; G.719: The First ITU-T Standard for Full-Band Audio (pdf).
When experimenting with a new audio path I like to take measurements. Long ago, in an age of techno-pre-history known as the late 1980’s, I craved what were then an emerging class of computerized test instruments, like the Audio Precision System One. Happily, today such costs are unwarranted given the current class of programmable smart devices. I’ve been very happy with Audio Tool For Android running on my Nexus 7 tablet.
If I am to trust the measurements that Audio Tool allows me to make I need to start by confirming the validity of it’s measure using a known reference signal. I was also making use of the Zoom H2 Handy Portable Stereo Recorder, so I decided to record the output of the sweep generator in Audio Tool to the H2. Then I tool the resulting WAV file into Adobe Audition to see what resulted.
After my little experimental effort with Opus in the freeware PhonerLite soft phone I reached out to a variety of people seeking advice about other software supporting this new codec. Someone suggested that I try Countherpath’s Bria. Counterpath is the…
Opus promises to be a great tool for online audio. In technology, as in music, not all opus are implemented equally. Allow me to explain.
Earlier this week I happened into a Twitter exchange with Mike Phillips. Mike is a podcaster. VUC founder Randy Resnick has introduced us once before. Mike is seeking a replacement for the role that Skype plays in his online toolbox.
It came to light that Mike has tried to leverage various soft phones, even giving some focus to finding one that implements the Opus codec. Opus is after all, open source, the current state-of-the-art in audio codecs, and a new IETF standard. However, in Mike’s attempts to tap its potential he has to date come up short relative to Skype.