[LAU] Open Source Audio Interface (was Successor/replacement for RME HDSP+Multiface?)

[Len Ovens]

On Tue, 2 Sep 2014, Kazakore wrote:

>> Madi can be sub-ms RT (return trip)
>
> Really? Coax, optical or both? I used MADI routers in my work but that was 
> more about sharing multi-channel audio across sites miles apart than 
> low-latency monitoring... (I also have to sadly admit the MADI system is one 
> of the ones I new the least about by the time I left that job :( )

It depends on distance, but it has almost no overhead compared to most 
other formats (besides analog and aes3). It depends on the dsp time used 
to split it up and route.

>> 
>> FOH snake use seems to require ~3ms RT
> Sounds like CobraNet at it's lowest latency setting (1.33ms per direction, 
> plus a little propagation delay.)

reading some of the formums dedicated to FOH kinds of things, it seems 
that yes less than 10ms is possible, but only with loss of channels and 
very clean network. It is a 3rd level network application, so it uses 
standard network SW and shares on an equal basis with other traffic. At 
most it asks for piority. It is like trying to do lowlatency audio with a 
generic kernel... shutting X and friends off and making sure nothing else 
really is running can give reasonable latency with only the odd xrun...

> I assume people have heard and read up on AES67? I admit I haven't beyond 
> skimming it and can't say I'm sure whether it's its own specification or more 
> about getting the various existing solutions to communicate together. 
> Probably worth reading though...
>
> http://www.aes.org/publications/standards/search.cfm?docID=96

I read some of the stuff about it. I do not have an AES account. Nor can I 
afford to buy a list of documents to find out about aes 50, 51, 53, 46? 
(one of those) and 67. 67 is for more wide spread content gathering from 
iphones etc. (If I have the right one, I have been reading too much the 
last few days)

The goal is to replace a local audio IF with something that has 
performance close to FW. With something that can be used on a laptop... 
even if it runs OSx. Something that can be used on stage as a guitar 
effect (funny, what we are talking about might be usable as an effect 
without a host :) or even a softsynth.... though I think a softsynth might 
do better with a host computer.

I had once thought that making an audio IF with enough power, one could 
add a drive and just use the host as an X server :)  Almost all the 
remarks I got were prefaced with "On any modern computer...".

In some ways I almost think taking some old ice1712 chips and connecting 
them to a PCIe IF might do more. Name your own favourite chip.

The only real problem with MADI is that it is hardware specific... old 
hardware... same as the ice chips, mostly not available.

Then there are laptops. None of them have a space for extra cards anymore 
(internally most of then have a single channel mini-PCIe, but I don't know 
how easy it is to use for audio). They have USB. So far USB is just barely 
usable, I don't know if the next generation of laptop will even have an 
ethernet port, they don't seem to be considered useful on small personal 
computing devices.

In the long run making a more powerful audio IF that can do more of the 
audio processing... possibly also running the main application, makes 
sense. In that case we really want that box to be open.

--
Len Ovens
www.ovenwerks.net