19 Nov
2008
19 Nov
'08
6:16 p.m.
Hi Folks
Whilst my 2.6.24.7-rt17 kernel and disabling all hardware and services
unneeded for audio seems to have gotten rid of those nasty xruns, I live
in fear that they will return. My main worry is how I organise my USB
devices.
My laptop (ThinkPad Z61m) has 3 USB ports. I have several devices that
need to be connected to them, meaning that I need to use USB hubs.
Here are some assumptions (or guesses) that I have made, on which I
would appreciate comment:
* It would be best to balance the devices across the 3 ports.
* My soundcard is a Behringer UCA202, capable of sampling at a maximum
of 48kHz @ 16bits x 2 channels. I'm guessing that this will have the
greatest data rate of all attached devices.
- Should it have its own port?
- Can USB 2.0 take more than this (like another device?)
- Anyone know how to set the sampling rate on this device through
Linux? Just specify in Jack setup?
* Now that I know that I can run USB to MIDI devices through a powered
hub (thanks David), I was thinking of of hooking the following into a
7-port hub:
- iPod cable (no iPod on the end, so no burden.)
- cellphone cable (as per iPod cable.)
- external USB QWERTY keyboard (don't have desk space for this
when doing audio work, so hope it won't be transmitting any
data.)
- trackball (only transmitting when wiggled (I hope) - which should
not occur when recording is going on.)
- USB floppy drive (not in use when recording.)
- USB to MIDI interface
- Another USB to MIDI interface - is it too much to have 2 of
these on the same hub? If not, would it take a third?
Cheers
M
--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
LinkedIn: http://www.linkedin.com/in/smiffy
19 Nov
19 Nov
9:16 p.m.
On Wed, Nov 19, 2008 at 5:16 PM, Matthew Smith <matt(a)smiffytech.com> wrote:
Hi Folks
Whilst my 2.6.24.7-rt17 kernel and disabling all hardware and services
unneeded for audio seems to have gotten rid of those nasty xruns, I live
in fear that they will return. My main worry is how I organise my USB
devices.
My laptop (ThinkPad Z61m) has 3 USB ports. I have several devices that
need to be connected to them, meaning that I need to use USB hubs.
Here are some assumptions (or guesses) that I have made, on which I
would appreciate comment:
* It would be best to balance the devices across the 3 ports.
* My soundcard is a Behringer UCA202, capable of sampling at a maximum
of 48kHz @ 16bits x 2 channels. I'm guessing that this will have the
greatest data rate of all attached devices.
- Should it have its own port?
Yes. This will probably use more bandwidth than all the other devices combined.
- Can USB 2.0 take more than this (like another
device?)
No USB 2.0 audio devices have Linux support AFAIK.
- Anyone know how to set the sampling rate on this
device through
Linux? Just specify in Jack setup?
Should work.
* Now that I know that I can run USB to MIDI devices
through a powered
hub (thanks David), I was thinking of of hooking the following into a
7-port hub:
- iPod cable (no iPod on the end, so no burden.)
- cellphone cable (as per iPod cable.)
- external USB QWERTY keyboard (don't have desk space for this
when doing audio work, so hope it won't be transmitting any
data.)
- trackball (only transmitting when wiggled (I hope) - which should
not occur when recording is going on.)
- USB floppy drive (not in use when recording.)
- USB to MIDI interface
- Another USB to MIDI interface - is it too much to have 2 of
these on the same hub? If not, would it take a third?
MIDI uses very little bandwidth, should work fine.
Lee
21 Nov
21 Nov
7:12 p.m.
Hiho,
On Wednesday 19 November 2008 20:16:24 Lee Revell wrote:
No USB 2.0 audio devices adhere to the usb-audio standard, and their
manufacturers have not opened up their protocol.
sincerely,
Marije
Whilst my
2.6.24.7-rt17 kernel and disabling all hardware and services
unneeded for audio seems to have gotten rid of those nasty xruns, I live
in fear that they will return. My main worry is how I organise my USB
devices.
My laptop (ThinkPad Z61m) has 3 USB ports. I have several devices that
need to be connected to them, meaning that I need to use USB hubs.
Here are some assumptions (or guesses) that I have made, on which I
would appreciate comment:
* It would be best to balance the devices across the 3 ports.
* My soundcard is a Behringer UCA202, capable of sampling at a maximum
of 48kHz @ 16bits x 2 channels. I'm guessing that this will have the
greatest data rate of all attached devices.
- Should it have its own port?
Yes. This will probably use more bandwidth than all the other devices
combined.
- Can USB 2.0 take more than this (like another
device?)
No USB 2.0 audio devices have Linux support AFAIK. 
20 Nov
20 Nov
5:24 a.m.
Matthew Smith wrote:
* It would be best to balance the devices across the 3
ports.
It depends. Usually, all ports are connected to the same controller and
have to share their bandwidth. The same is true for all ports of a
single hub.
* My soundcard is a Behringer UCA202, capable of
sampling at a maximum
of 48kHz @ 16bits x 2 channels. I'm guessing that this will have the
greatest data rate of all attached devices.
USB 1.1 can transport six channels. (In USB 1.1 mode, the SB Audigy 2 NX
just barely manages eight channels, but leaves practrically no bandwidth
for any other devices.)
- Can USB 2.0 take more than this (like another
device?)
No, all communication with USB 1.1 devices is at full speed, not high
speed.
It's different with full speed devices connected to a USB 2.0 hub; in
this case, the computer and the hub communicate at high speed.
To use multiple USB 1.1 devices that together would exceed the bandwidth
of a single USB 1.1 bus, you need to connect each one to a USB 2.0 hub.
(Or use two separate USB controllers, but only the latest mainboard
chipsets that support 12 USB ports have them.)
- external USB QWERTY keyboard (don't have desk
space for this
when doing audio work, so hope it won't be transmitting any
data.)
- trackball (only transmitting when wiggled (I hope) - which should
not occur when recording is going on.)
Input devices must be polled by the computer; not using them doesn't
save much bandwidth.
Furthermore, all communication with low-speed devices runs at low speed,
so they use up as much bandwidth as a full-speed with with eight times
the same data, or a high-speed device with 320 times the same data.
Best regards,
Clemens
5851
days inactive
5853
days old
linux-audio-user@lists.linuxaudio.org
3 comments
4 participants
participants (4)
-
Clemens Ladisch -
Lee Revell -
Matthew Smith -
nescivi