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Old 19th July 2008, 05:13 PM   #15
Francis Vaughan
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Join Date: Jan 2008
Posts: 537
Quote:
Originally Posted by triez View Post
USB sends data in packets while Firewire streams continuously. You can send 72 channels of Audio down a Firewire cable, I've personally never seen more than 4 down USB.
This isn't quite right. FW is packetised. FW runs a cycle clock of 8kHz, and any member of the bus that wants to send something on the bus can request a time slice to do it. Isochronous devices (which all audio devices tend to be) are able to pre-book the slices they need, and thus are always guaraneteed that they can send. So in a sense they stream - but only in that they are pre-booked and do not need to negotiate (and maybe fail) to get the slice needed. This indeed is a huge win over USB which provides no such mechanism. But inside the time slice, a packet is what is sent.

(It is interesting to notice that the 8kHz cycle clock is the same frequency as used on SDH and SONET for long haul data telco level data communications. Much the same problems are being solved in similar ways.)
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