[Liverpool] Silent PCs

[Bob Ham]

On Fri, 2011-06-17 at 20:58 +0100, Sebastian Arcus wrote:

> I know where you can get some 12M (~36feet) USB extensions ;-)
> 
> There seem to be plenty USB audio mixers out there.

USB audio is bad for a number of reasons (which escaped my recall until
I consulted with one of my fellow Linux audio developers :-)

1. Low bandwidth
2. A fixed bus cycle length of 1ms.  This limits the sample rate to
   48 or 96 kHz.  Anything other than that will introduce jitter¹.
3. Holes in the audio device class specification causing variations in
   the operation of different devices.


I have two PCI soundcards² (synchronised), each with 2 digital and 8
analogue input channels, and 2 digital and 8 analogue output channels.
This gives a total of 20 channels at 96kHz in each direction, with the
low latency and bandwidth of the PCI bus.

I don't think a USB bus would be able to handle the bandwidth.  Even if
it could, the latency would be bad.  From another room, I would be
surprised if it was usable.


USB audio is fine for connecting your webcam's mic.  For proper audio
work, it's best to stay clear :-)



¹ http://en.wikipedia.org/wiki/Jitter
² http://www.m-audio.com/products/en_au/Delta1010.html

-- 
Bob Ham <rah at bash.sh>

for (;;) { ++pancakes; }
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