On 05/05/2014 03:21 AM, Stephen Hurd wrote:
If it all works out, I just thought of a new mode that may be worth
playing with... using left/right channels to enable full duplex use
with a single sound card. Not sure if sound cards generally have
enough isolation between the channels though, so it may not work very
well in real life. This would likely end up waiting until I build a
new rig interface though.
Yes, this has been discussed previously and the result of a test would
be interesting. One issue is that you are going to have to disable any
OS use of the sound card.
Cheap sound interfaces are something else that need tons of testing on
multiple platforms, it would be nice to be able to specify a reliable
one. If you can find one with USB 2 speed it's much more likely to work.
No USB 3 ones are available at reasonable prices yet. I have these
problems with some USB audio interfaces even though they are rather
expensive ones:
Failure to negotiate properly when plugged in.
Insufficient bandwidth when operating, even though I have them
plugged direct to the motherboard.
Certainly the Linux driver can be at fault, but in general USB devices
are poorly implemented and the OS driver does its best to cope with
them. What I see on Linux is like these:
[581624.032956] usb 1-8: new full-speed USB device number 38 using xhci_hcd
[581624.059098] usb 1-8: New USB device found, idVendor=0763, idProduct=201d
[581624.065905] usb 1-8: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[581624.073132] usb 1-8: Product: Producer USB
[581624.077319] usb 1-8: Manufacturer: M-Audio
[581681.065462] xhci_hcd 0000:00:14.0: Signal while waiting for
configure endpoint command
[581681.073476] usb 1-8: Not enough bandwidth for altsetting 0
[581712.630467] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called
with disabled ep ffff880831b77880
[581712.639649] xhci_hcd 0000:00:14.0: Trying to add endpoint 0x84
without dropping it.
[581712.647400] usb 1-8: Not enough bandwidth for altsetting 2
[581712.652983] 38:2:2: usb_set_interface failed (-22)
These are extracted from a few pages of messages after plugging in a USB
2 hub with 4 audio devices, 3 of which are a Via USB dongle and the
other is a CM106 clone:
[1604966.737023] 66:1:1: usb_set_interface failed (-110)
[1605113.571615] usb 1-6.3.1: new full-speed USB device number 78 using
xhci_hcd
[1605113.578858] usb 1-6.3.1: Device not responding to set address.
[1605113.791300] usb 1-6.3.1: Device not responding to set address.
[1605114.000897] usb 1-6.3.1: device not accepting address 78, error -71
[1605114.007681] hub 1-6.3:1.0: unable to enumerate USB device on port 1
You know it's broken when you can't even get the device to enumerate.
Thanks
Bruce
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