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linux or celliax compatible usb sound devices

Sun, 2007-09-09 12:03 — ka3ax

when you build celliax-based gms termination the most limiting factor you face is the amout of lines per pc. couse you can use 4 pci (and/or isa?) soundcards. this gives you 4 (or 8 with asla hack?) lines.

correct me please if I am wrong.

can we use usb sound devices? which of them are tested/compatible? how many lines are available with this method? some motherboards have 4-8 usb ports onboard and we can use usb hubs also. pci-usb adapters are also available. how many channels (usb sound device + usb datacable) can we connect to one usb port?

the theoretical datatransfer limit for usb2 is 480 mbps. which bandwith do we need per channel (usb sound device + usb datacable)? or should we also take into account some other factors (delays etc...?)

i searched and read forum here... it is not discribed clear and directly. just couple of details mentioned here and there. give me the link please if the question discribed somewhere.

thanks


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Sun, 2007-09-09 13:53 — gmaruzz

usb sound

usb sound is managed by one only "model" of driver in linux (the "generic" one), and is well supported by alsa.
Alsa, generally speaking (eg. not just for usb audio) supports a max of 8 devices, but this can be changed at the kernel level (dinamic minor number allocation)

the problem with usb sound is that:
1) if you connect them (usb soundcard are usb 1.1) through a usb 2.0 hub, you can have very different and bizarre problems, at least until some months ago. I know there have been many improvement to the USB management in the linux kernel, so maybe this is fixed now
2) the cheap "pen drive shape" usb soundcard can be bad quality, the "high end" usb soundcard can be proprietary and not supported by linux
3) anyway, it's not a bandwidth problem (notwithstanding the error message you can have from the usb subsystem), it's a USB protocol management problem of the linux kernel.

So, it all boils down to: test them and find what works better for your machines (yes, the kind of internal usb hub in the pc can make a difference).

Please, let us know how is going, the good and the bad.

no problem with usb datacables, you can have how many you want


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