8 Nov
2009
8 Nov
'09
5:56 p.m.
On Sun, 8 Nov 2009 16:53:31 +0100 (CET)
karl(a)aspodata.se (Karl Hammar) wrote:
Folderol:
...
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.
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) ? Shall I interpret your answer as the main hurdle is
not to convert
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?
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.