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James Cameron wrote:

quoted text
> On Tue, Sep 08, 2009 at 10:14:24AM +0100, andy baxter wrote:

>

>> - using a program which turns the computer keyboard into a virtual midi

>> device. This makes the sound much more immediate. Having tried this, the

>> contrast makes it obvious that there is still a problem with delays from

>> the edirol keyboard.

>>

>

> Interesting.  Let's consider that data path further.

>

> 1.  flow from keyboard USB device to USB controller,

>

> 2.  an interrupt,

>

> 3.  flow from USB controller to processor.

>

> Perhaps another device on the system is preventing the USB interrupt

> from being processed in a timely fashion.  See if you can quieten

> devices one by one and see if the problem changes.  For example you can

> quieten a graphics driver by switching to the text console and then

> resume playing the MIDI keyboard.

>

>

I've tried running qsynth and jackd from the console with no x session

running, and this still doesn't cure the problem. Neither does bringing

down the network interface.

quoted text
> General suggestions for a USB flow rate problem ... try different USB

> sockets, remove as many USB devices as possible, ensure the cable is

> as short as possible, ensure the cable is standards compliant, and if

> there is a way to power the device differently (e.g. a DC input socket),

> then try it.  I've even had particularly strange devices behave better

> on a powered hub.

>

>

OK. DC power is tricky for me but could try it. I've tried all the

sockets and it makes little or no difference.

quoted text
> Your lsusb shows the device is attached to a USB 1.1 hub.  There is a

> Freecom Technologies device attached to a USB 2.0 hub.  This might be

> because the keyboard is only USB 1.1 complaint, I don't know.

>

> Watch /proc/interrupts while trying to play, and see what counters

> increment in the matrix.  Here's a fun way ... run this in a terminal

> window while playing keys on the MIDI keyboard ...

>

> 	watch -d --interval=0.1 cat /proc/interrupts

>

>

I've tried this (nice trick!). It's hard to get precise numbers, but

roughly the interrupt rates are:

int 0 - timer - 700-1000 per sec.

int 17 - sound card - 300-500 per sec.

int 21 - edirol keyboard usb hub - 30-50 per sec.

LOC - local timer - 150-200 per sec.

RES - Rescheduling interrupts - 1000-1500 per sec.
> What is the kernel version?  You mentioned Debian Testing and Ubuntu

quoted text
> Jaunty.

>

2.6.26.8-rt16 on debian testing.

quoted text
> I've looked at the 2.6.30 sources (latest stable), and the USB device

> you showed us in lspci "0582:0033 Roland Corp. EDIROL PCR" is listed in

> sound/usb/usbmidi.c and also in sound/usb/usbquirks.h .  There was

> nothing funny about the quirks.

>

> I've looked at the Ubuntu Jaunty 2.6.28 sources, and usbquirks.h for

> this device is no different.  usbmidi.c *does* have differences, in that

> there have been several fixes in 2.6.30 that might be relevant.  Nothing

> about the changes looked like an exact match to your problem, but that

> could be my inexperience.

>

> I suggest you try downloading and booting from the Ubuntu Karmic Alpha

> CD images that are available now.  The newer kernel in those images may

> change the timing problem for you.

>

>

OK will give this a try at some point.

Cheers for the help.
andy
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