AVnu: Getting Streaming Audio Right
By Chris Heinonen on
When you wire up a pair of speakers, you probably are unconcerned with getting the timing correct. Signals traveling over copper speaker wire are moving at a speed measured relative to the speed of light. Having one cable be a few feet longer than the other will not make a measurable change in when the signal reaches each speaker.
Now that we are moving to wireless speaker systems, be it Sonos or Samsung or using Airplay, we no longer have copper wire carrying the signal to each speaker. Our music source might have to send the same signal to multiple speakers, each with their own audio clock(s), over different paths to get it there. Now how do you know the the same signal is getting to the speakers at the correct time and rendering at a common rate? Will one speaker play earlier and destroy the stereo image?
The AVnu Alliance has been working on this problem and came up with a solution called AVB (Audio Video Bridging), based on IEEE open standards. AVB isn’t a new transmission standard or format, but instead a lower-level feature that works with connected devices. Instead it adds a timing signal to your existing Ethernet or Wi-Fi devices that allows them to remain in sync. Every device also receives a master clock signal and then uses that to decide when to play music to keep it in sync.
Being an open standard means that everyone can implement it. As almost every wireless music system out there utilizes Wi-Fi as their transmission system, adding in AVB support is possible to do. It also means that products from different companies can be compatible with each other. You could buy a pair of speakers from Samsung and a pair from LG and they can work together.
Wireless audio has long had the perception of not being truly high-fidelity. It has been a convenience for which you are willing to give up some quality. With true lossless, CD quality streaming being available in many systems now this is no longer the case. Resolving issues about interoperability and timing will only further eliminate downsides associated with streaming audio. Having truly high-quality, wireless audio systems will let people listen to music more easily.
AVB is still 1-2 years off for consumers at this point. Hardware chipset manufacturers are starting to add it in right now. OS X on Apple computers supports it already as a version of it is being used with professional music systems for concerts and other venues. Once products start to appear with this, it has not been decided how to make consumers aware of it, yet. With one more obstacle removed, a future of high-performance, wireless audio is closer than ever before.
Is there any development kit? Where can we find some up to date specifications? The current drafts don’t seem to consider a wireless connectivity
Chris Heinonen says
You can find current specs and white papers on their site: http://avnu.org/knowledgebase/
I already did that and it seems to be only one “Automotive Ethernet AVB Functional and Interoperability Specification” document. Is it safe to assume that currently there is no spec for AVB over wireless networks?
Chris Heinonen says
You can also look here for info on AVB with 802.11: