.WAV over LAN

[ef37a]

Hi,
It seems a simple thing to this simple mind but I cannot find any information about this apart from expensive hardware solutions.

I have 2 pc's and a laptop copper networked. Is it easily possible to send in realtime the audio digital op of one to the soundcards of the other two?

Having just typed this out I realize I need an input called something. I have Delta 1/2 and S/PDIF or Fasttrack1/2, etc.
It seems I lack an input such as LAN 1/2 or LAN L/R?

Must be some software surely? I have dabbled with MIDI over LAN and that works.

Dave.

[dmills]

It is actually a little hairy to do unless the soundcards at both ends are locked via wordclock or similar, you need a resampler and delay locked loop to compensate for clock drift.

Now it can be done, and in the unix world, things like nas, netjack and pulseaudio manage to pull it off, but I am not aware of much on the windows side.

Regards, Dan.

[ef37a]

Thanks Dan,

Now be aware I ask this in all ignorance, I am not arguing!

Why does each end need to be locked? I can send S/PDIF pc to pc and just lock the 2496 to the incoming. Why not with a LAN derived signal pretty please?

BTW I am quite happy with 16bits at 44.1kHz.

Dave.

[dmills]

Because SPDIF has a built in clock transport.

The issue is that with the network transport, the two sound cards are only running at nominally the same rate, say both cards are running at (theoretically) 44.1K, the reality might be that one is running at 44.099Khz and the other is running at 44.102Khz.
Now with the spdif link, the one on the receiving end will pull its clock to match the data rate on the spdif link, so both cards will run at exactly the same rate, and support for this is built into the card hardware.

With the network link, the sending end will (probably) generate a packet every time the card fills a buffer, but the receiving card will not be actually accepting the data at quite the same rate (Because the clock is not locked to that of the sending card), thus you need some software at the receiver that resamples the data based on an estimate of the very slight difference in clock rates.

Further note that the clocks both change rate over time, so the rate estimator has to track the slowly time varying clock rate differences.

As I say, it does work, but robust implementation is a slight pain.

Regards, Dan.

[Dave B]

Google 'Wormhole 2'... this is a plugin that lets you set up audio 'tunnels' over the network between DAWs.

[ef37a]

Thanks Dave,
Will give that a do.
BTW chaps, how does radio work over a LAN then?

Dave.

[dmills]

By running well behind realtime and deliberately buffering a **LOT** of audio (And by not being afraid to skip occasionally). Comparing the streaming radio with an FM one can be instructive in this regard.

Things get a lot more tricky when you try to do this at low latency!

Regards, Dan.

[_Nuno_]

Thanks Dave,
Will give that a do.
BTW chaps, how does radio work over a LAN then?

Dave.

It's very different. Radio is not realtime and there's no need for synchronization. There's also no great concern with reliability with a radio broadcast, if you miss a packet, they won't resend it for you. As far as I know radio over the net uses UDP usually because of this.

[ef37a]

Very sorry Dan I have asked slightly the wrong question and used a term, realtime, improperly.

I don't mind latency, just the ability to run audio into the next room over an existing LAN will be fine and CD quality, or MDisc even, would be suficient.

Dave.

[The Elf]

I may be oversimplifying what you're trying to do, but if you have audio files in your Media Player Library and set the library to 'shared' then you can play audio anywhere else on your LAN by telling the other Media Players to find any shared libraries on the network (for some reason I could never get this working reliably on Windows XP, but everyone seemed to - Vista is much better at this)

I actually use a more knuckle-head way of doing it by setting my main 'My Music' folder on my Office PC as a network drive, but the above is slicker.

Not real-time, or anything fancy, and not sure it matches what you're looking for, but may be of interest...