Oh and of course you have the Open-AVB project first started by Intel.

Looks like folks are talking about getting it running on a BeagleBone or iMX6 based board: 

On Sun, Jun 7, 2015 at 12:08 PM, Jesse Cobra <jessecobra@gmail.com> wrote:
Just a few notes, not sure if this is of any use:

Motu and Presonus are now shipping some semi-affordable AVB audio devices and switches. The Motu switch is $295.

All shipping Apple hardware supports AVB, via the BroadCom NIC they are using. You could of course install Linux on said hardware.

Any computer using the same BroadCom chipset can also support AVB. For Windows Echo Audio was making an AVB to ASIO application for this. Again you could install Linux on any of these computers.

The NIC that the FreeScale iMX6 and Texas Instruments AM335x (of which the BeagleBone is based) can support AVB. Some audio companies are shipping closed AVB products based on the AM335x and iMX6 that use Linux.

I know of one developer who was thinking of making his AVB stack for Linux on AM335x BeagleBone open source but currently it remains a closed solution.

Then of course you have the XMOS reference design but that has nothing to do with Linux.

I think the cost to do this is becoming a non-issue, with a $200 switch and a BeagleBone based audio interface it should be possible to make a cheap AVB solution on Linux.

Just my 2 cents...

On Sun, Jun 7, 2015 at 7:15 AM, Len Ovens <len@ovenwerks.net> wrote:
On Sat, 6 Jun 2015, Reuben Martin wrote:

I thought I would post this since there was a big conversation here a while back about AES67 and the slow death of AVB due to lack of support.

Well I was talking with a guy from Meyer Sound who told me that AVB has been resurrected from the dead. Apparently Cisco and other large network hardware vendors were willing to back it as long as it was made more generic to accommodate industrial uses that are also time-sensitive.

So apparently it has been re-branded as “Time-Sensitive Networking” and has a lot more momentum behind it.



Some notes on AoIP and Linux. There are some well funded people/companies that use Linux for many things, but much of the development in the audio world is with people who have hardware that they can't afford to replace and so write drivers for. I think this is part of the reason we are not seeing much in the way of Linux drivers for AoIP (AVB, AES67, Ravena, whatever). Right now, AoIP on Linux costs about twice as much as a normal audio card because the Linux box requires both an interface card in the computer as well as the Audio IF on the other end of the network cable (not to mention a switch in the middle).

Why is this? Linux is based on lowest common denominator hardware... we call it the PC. The Linux world has gotten much better preformance out of this box than it was designed for. But, in the case of audio, the HW does limit performance at least with AoIP. That limit is the clock. The PC does not have a HW PTP clock built in and in this case software is not good enough. The way around this is with a custom NIC that does. For some reason even though one can buy an ethernet chip that includes a stable PTP clock for less than $5, any NICs I have found with a PTP clock are closer to $1k.

I was "listening in" on a IRC conversation about the differences between ALSA and Core audio and why Core audio "does it right". The difference ends up being this HW clock. That is ALSA is build the way it is because the PC requires it to be.

Whats the point of all this? TSN sounds good to me. It widens the scope of low latency networking and the requirement of distributed clocking into areas where cost matters. I am hopeful that this means the cost of a NIC with good HW clock will go down or even become standard. All kinds of AoIP would see the benefit from this. I also think the cost of AoIP audio interfaces would come down to similar cost as USB or firewire.

There is no reason we could not make an ALSA AES67 driver that would work with any GB-NIC out there but the closed drivers now available show that on a PC latency is double that of Core audio and handles fewer channels.
(Core audio at 192K = 64 channels in and out min latency 32 samples, Win at 192k = 16 channels in and out min 64 samples) So any ALSA driver would suffer from similar lower performance. This is why almost all AoIP setups suggest their PCI(e) card in place of your stock NIC.

* numbers from:
I have seen similar numbers (or worse) elsewhere.

* I am not in any way suggesting anyone use 192k sample rate for audio recording or streams. It's use here is only to show the difference in HW capabilities. 48k is what I use and suggest others use.

Len Ovens

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