[Jack-Devel] new IIO driver added to jack - large overruns

Hi there,

I have added a new IIO driver to jack.
IIO is Industrial IO and it is for devices with high sample rates.
Currently it is only partially tested with devices which have the 
AD7476A chips onboard - they have a 1MHz sample rate which is rather 
nice :) However I have a problem ... please read on ...

As I don't have write access to the original jack1 repo, I have forked 
until I do. For now you can find it here :
https://github.com/flatmax/jack1

You will also need the git repo for gtkiostream, as it uses this code :
http://www.flatmax.org/gtkiostream/html/classIIO.html

This new IIO driver is in alpha mode... I am currently testing on an ARM 
board however I get large overruns for some reason ...

Here is an example when running 'jackd -r -d iio' :

created iio driver ... iio_pcm|1000000|1024|1024|4|0
iio_driver_start::   enabling IIO : enable(true)
iio_driver_wait
iio_driver_wait
**** iio: xrun of 97145 usec
iio_driver_wait
**** iio: xrun of 81626 usec
iio_driver_wait
**** iio: xrun of 80022 usec
iio_driver_wait
**** iio: xrun of 79894 usec
iio_driver_wait
**** iio: xrun of 79856 usec
iio_driver_wait


I am actually wondering whether anyone can help me with some information ?
I run the driver with zero load ... it doesn't ever try to read anything 
from the actual devices ... however it appears that jack on the ARM 
board is giving Xruns of the order of 80 ms !

This is even when the driver_read function is as follows :
static int iio_driver_read (iio_driver_t *driver, jack_nframes_t nframes) {
   return 0;
}

The relevant driver code is located here :
https://github.com/flatmax/jack1/blob/master/drivers/iio/iio_driver.C

It uses the g++ compiler because it instantiates the IIO class from 
gtkiostream to do the heavy lifting.

Matt

1390210559.4511_0.ltw:2,a <52DCEDF3.1030305 at flatmax dot org>