Re: [Discuss-gnuradio] USRP-Overrun Problem

[Eric Blossom]

On Sun, May 09, 2010 at 04:01:48PM -0400, Marcus D. Leech wrote:
> On 05/09/2010 02:57 PM, Eder Matthias wrote:
> > Hello,
> >
> > i'm newbe at Gnuradio and i started with a simple FM receiver project.
> > I use a USRP1 interface with a TV Rx rev3 daugtherboard and gnuradio
> > 3.3, installed on a Ubuntu 9.04 distribution.
> > The CPU is a AMD X2 4800+, ramsize is 1GB.
> >
> > The good news: The FM-receiver works very well.
> > The bad news: "uOuOuOuO"-messages
> >
> >
> > The USRP parameters are:
> > freq: 102,4 MHz
> > decimation: 256
> >
> > Realtime scheduling is enabled too.
> >
> > The decimation factor of 250 devides the full usb bandwith of 64MB/s
> > to 256kB/s.
> > In my point of view, this should be no problem for the pc to read this
> > amount of data.
> > Nevertheless i get many of the overrun messages ("uO").
> > The effect of the lost messages is hearable to (of course!). I can
> > hear a cyclic! click.
> >
> > That means, that the pc isn't able to read the USB data fast enough.
> > But why?
> > The CPU load is about 15% of each core. But gnuradio isn't listed in
> > the process-list. So i cannot say what load is produced by gnuradio
> > itself.
> >
> > Does anybody can give me any hint, where the problem could be?
> >
> > Thank you for your help.
> >
> > Matthias
> >
> >
> I'd look at the existing USRP example FM receiver to get some hints
> about how to handle
>   the two-clock/two-buffer problem.

The proper fix needs to go in the audio sources and sinks.

Although there is an "ok_to_block" constructor argument, most of the
implementations ignore it.  Please feel free to fix.

Eric