linuxaudio.org

On Sun,  8 Nov 2009 16:53:31 +0100 (CET)

karl@aspodata.se (Karl Hammar) wrote:
> Folderol:

quoted text
> ...

> > I started looking at the USB2 protocols for something else, but gave up

> > when I saw how insanely complex it is even for relatively simple data

> > transfer. In the end, for my project, it was easier to convert the data

> > into an RS232 serial stream then use one of the standard serial-USB

> > converters.

>

> Well, then you could design around a ft232 [1].

> But would RS232 suffice for 8ch/24bit/44.1kHz (12Mbit/s) ?

My project was relatively slow speed. RS232 wouldn't begin to come close

enough for even 1 channel :(

The FTDI chip would just about manage one channel, but I don't know how

you'd convince the host computer that such high baud fake serial is

possible.
> Shall I interpret your answer as the main hurdle is not to convert

quoted text
> x channels at real time, but to get it into the computer?

Indeed. the conversion itself just requires a very stable clock signal

and an accurate ADC for every input and DAC for every output - well

that's the theory :).
Getting that lot into the computer - now that's the art! I'm not aware

of any open designs, even for a pretty basic sound card, which must

tell its own story.
> Would a network connection solve that problem?

quoted text
> In that case the DACs and ADCs could reside on an embedded computer

> and stream the sound data to/from the pc. And one could envision

> such little things near each mic and ethernet cables or possible wifi

> to the control room. Power-Over-Ethernet [2] could be helpful, and why

> not throw in a pre-amp and plug it directly into the mic.

>

> Regards,

> /Karl

>

> [1] http://www.ftdichip.com/Products/FT232R.htm

> [2] http://en.wikipedia.org/wiki/Power_over_ethernet

Ethernet looks interesting, and I know there is stuff out there, but

have no idea what latency and timing issues there may be. I would

imagine syncing multiple 'drops' to a stable clock might be problematic.
If you're just multicasting an audio stream neither of these is

especially important.
P.S.

I could be quite wrong about most of this - it has been known to

happen :)
--

Will J Godfrey

http://www.musically.me.uk

Say you have a poem and I have a tune.

Exchange them and we can both have a poem, a tune, and a song.

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