Re: [libdc] More than four cameras on a single bus

[Stefan R. <st...@s5...>]

Martin Habbecke wrote:
> I have read somewhere that some controllers are limited to 4 
> isochronous streams. Is that true? And is there a way to find out how 
> many streams my (on-board) controller supports?

Yes, and yes.
$ dmesg | grep ohci1394
ohci1394: fw-host0: OHCI-1394 1.1 (PCI): IRQ=[18] 
MMIO=[fd8ff000-fd8ff7ff]  Max Packet=[4096]  IR/IT contexts=[4/8]
ohci1394: fw-host1: OHCI-1394 1.1 (PCI): IRQ=[20] 
MMIO=[fbffd000-fbffd7ff]  Max Packet=[2048]  IR/IT contexts=[4/8]
ohci1394: fw-host2: OHCI-1394 1.0 (PCI): IRQ=[17] 
MMIO=[80000000-800007ff]  Max Packet=[1024]  IR/IT contexts=[4/4]

The number of IR contexts is one of the limits for the maximum number of 
streams you can capture at once.  (Here: 4 contexts at each of these 
controllers, TSB82AA2, VT6307, NEC-something.)  There are other limits 
too of course, notably FireWire bus bandwidth.

> Moreover, can anyone 
> suggest a firewire controller that allows for synchonously capturing 
> with more than four cameras?

Looks like only Agere controllers implement more than 4 IR contexts.
http://www.ptgrey.com/support/kb/index.asp?a=4&q=146

Also related:
http://www.ptgrey.com/support/kb/index.asp?a=4&q=22
-- 
Stefan Richter
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http://arcgraph.de/sr/