On 11/12/2012 02:10 PM, Tom Hendrick wrote: > > > Hello Josh, > > Thanks for the suggestion. Yes I had zero padded the file with about 1 > second of zero signal prior to the signal I want to transmit. I had still > seen the blip/noise when running the script even when there was 1 second of > zero padded signal. Is there anything else I should try? >
Well, then perhaps it not the result of an underflow. What is your transmit amplitude? In the old libusrp1 floats were +/-2**15, but now they are +/-1.0 fullscale. So you must have had to adjust the amplitude of the baseband samples; but are they scaled small enough to avoid truncation? -josh > Thanks, -Tom > > > ________________________________ > From: Josh Blum <j...@ettus.com> > To: discuss-gnuradio@gnu.org > Sent: Monday, November 12, 2012 1:03 PM > Subject: Re: [Discuss-gnuradio] UHD Underrun with Wav File Source and USRP > Sink > > > > On 11/11/2012 01:21 PM, Tom Hendrick wrote: >> Hello all, >> >> I am using a USRP1 and an LFTX daughtercard and Ubuntu 12.04. >> >> I am having an issue with a simple GRC script I made which has three >> blocks. A WAV file source connects to a resampler block and then to >> the UHD USRP sink. >> >> When I run the script I get a single underun right at the start of >> running the script and no other underrun. When I run the script using >> the sudo in front of it, I get two underruns right at the start of >> running the script and no other underrun. I monitored the signal out >> of the LFTX using an oscilloscope and noticed some blips/noise when >> the script is run and I believe they correspond to the underruns. I >> tried this with and without real-time scheduling enabled and didn't >> see any difference. >> >> >> I tried the same exact type of script with an older version of GRC on >> a different laptop with Ubuntu 10.04. This uses the USRP sink block >> not the UHD sink block. This script plays the file perfectly without >> any underruns at all and I don't see the blips/noise at the beginning >> of the signal. >> >> I am using the LFTX for an audio application and the blips/noise will >> cause a problem for me. Does anyone know why I am seeing this >> behavior with the newer UHD block? Is there anything I can do to >> eliminate it? >> > > Hi Tom, > > If I am understanding correctly, you are getting some initial underflows > when the flow graph begins processing. This is causing some > discontinuous stream interruption over on the receiver side. > > If thats the case, I dont know of anything specifically to cause this, > so it might just be the issue of interrupt coalescing. That is the host > isnt initially ramped up to push out USB packets at full speed. So, > driver wise, there may have been a subtle difference thats brining this > out, USB 1.0 vs .1 for example. > > I'd like to replicate it over on end. But if I have a quick suggestion, > it may be helpful to zero-pad the beginning of the wavefile so those > initial discontinuities are only lost in the padding. > > -josh > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
