13 Nov
2009
13 Nov
'09
12:43 p.m.
Folderol:
Giso Grimm <gg3137(a)vegri.net> wrote:
...
> b) own protocol, multiple OSHw, master clock:
>
> Master Clock
> Host sound card
> ||
> jackd <===> OSHw
> <===> OSHw
> <===> OSHw
...
It appears there is a software suite for the
'other' OSs that can
manage 16 channels of 48k over the Internet (not just a LAN) provided
you have an upstream of greater than 150Mbps and downstream better
than 750Mbps.
Then, beginning with 8channels on a lan would be a starting point.
When that works we can add channels as see what happens.
Also, there is a very useful looking fully
self-contained Ethernet chip
that can deliver 25Mbps at application level. This is the WIZnet W5000.
It can also open up to 4 sockets, so I'm not clear as to whether that
is 25Mbps per socket, or in total.
I found [1]. On a 100Mb/s net it must be "total". In a simple test a
few years ago I got 50Mb/s between two ordinary pcs.
Very empirically speaking, with 1 channel at 24 bit
depth that's a
potential sample rate of 1MHz,
Isn't the sample rate something like 44.1, 48, or 96kHz ?
Data rate for 1ch * 24bit * 48kHz = 1.152 Mb/s (+overhead).
or putting it another way 20 channels of
48k! OK, OK, I know I'm leaving out huge swathes of control, collisions
etc. :)
So, if we have multiple 100BASE-TX trough a gigabit switch to a pc with
a 1000BASE-T, we "shouldn't" have any problems with the network
performance with < 100 channels...
Or on with a simple crossed cable only 100Base-tx network, it should be
possible to transfer 30-40 channels.
...
Being a bit simplistic if you have a master clock (not
necessarily
the computer) send just a timecode at 48kHz everything can lock on to
this immediately, and keep updating its copy of the timecode.
For a network solution, that would be the job of PTP (ieee1588) it seems.
Something wanting to transmit audio would then send
back it's own ID,
the current timecode followed by up to 24bits of A/D stream.
Packets would be small and latency low, buffer size could probably also
be quite small.
The computer would pick up all the incoming data streams and sort them
into their appropriate channels and time points. At this level, the
occasional out of sequence packet could probably be put back into it's
right place with only a relatively small additional buffer - well I
hope so!
...
So this would be like Giso's "own protocol" alternative b above ?
Regards,
/Karl
[1] http://www.wiznet.co.kr/en/data/WIZnet_e-brouchure_2009.pdf
-----------------------------------------------------------------------
Karl Hammar Aspö Data karl(a)aspodata.se
Lilla Aspö 148 Networks
S-742 94 Östhammar +46 173 140 57 Computers
Sweden +46 70 511 97 84 Consulting
-----------------------------------------------------------------------