I don't have an answer to this, but I just discovered http://raspberrypi.stackexchange.com
I've been ending up at Stack Exchange for several years whenever I search for answers for technical issues, I didn't know there was a special place on there for the Pi. I'm just looking at building a kernel on mine, I've done it once on i386 Debian years ago but mostly I use OpenBSD and FreeBSD on i386/686. rtl-sdr works on mine, last I knew. Alan ----- Radio Astronomy - the ultimate DX -------------------------------------------- On Wed, 4/16/14, Robert Nickels <[email protected]> wrote: Subject: Re: Buffer underrun on raspberry pi To: [email protected] Date: Wednesday, April 16, 2014, 2:50 PM On 4/16/2014 12:02 PM, David Radakovits wrote: > Hi! > So i finally got the rtl-sdr "working" on my raspberry pi. > What i have now, are buffer underruns when i type > > rtl_fm -f 87900000 -M wbfm -s 200000 -r 48000 - | aplay -r 48k -f S16_LE -t raw -c 1 > > i had those underruns too on ubuntu which i ran in virtual box on my mac, > but i didn´t get them on a notebook running xubuntu, everything was working fine there. > any ideas why i get them and how to fix it? > David, I and others have been working this issue on the Raspberry Pi forum, as the root cause has been identified as an unintended side-effect from a recent kernel change. For details see: http://www.raspberrypi.org/forums/viewtopic.php?f=28&t=72545 and related threads. The issue affects other ALSA applications and the issue has been opened on github. At least one user has reverted to a previous kernel version which does eliminate the problem, but creates new ones in terms of keeping the Pi updated. One experiment you might try is to run top in another console while you're experiencing the buffer underruns - CPU utilization should be running <20%. Then run top again using this command option: top -d .01 (causing top to update almost continuously). In my case, anything like this that prevents the CPU from becoming idle allows the audio from rtl_fm to stream without interruption. Hopefully the linux kernel developers will be fixing this soon, especially with the recent improvements that have been made to rtl_fm. 73, Bob W9RAN
