[Jack-Devel] jack2 crackle sound problem on bbb - jack_bufsize?

dear collected wisdom, i have a tough problem to solve with jackd messing up my input sound. it’s a reoccurring crackling on the input channel that sounds a bit like pulsewave ring modulation. i figured out it’s highly dependent on my blocksize settings. for example: with -p1024 the distortion starts every 7th minute and lasts for 2min50sec. with -p512 the distortion sounds slightly different (like with a higher ringmod freq) and starts every 3min15sec and lasts for ~1min. with -p256 it appears every 1min45sec and lasts for 40sec. etc. after much research i found this... http://thread.gmane.org/gmane.comp.audio.jackit/28114/focus=28115 and this… http://music.columbia.edu/pipermail/linux-audio-user/2005-August/025787.html that i believe describe the same issue. as suggested in those posts resetting the jack_bufsize makes the distortion go away. but only temporarily - it always comes back after exactly the same time! for now i can let my system reset the buffer after a known time interval, but that’s a really ugly hack and i’d be happy for suggestions on how to solve this. below are details of my system. i compile jack2 from master and it’s all running under debian wheezy on a beaglebone black. i use supercollider 3.7 and a terratec aureon dual usb soundcard. i’ve also tried with another usb soundcard (C-MEDIA) but then the crackle occurs on the output instead (and also after longer intervals). so same issue but sounds worse. thank you, _f BeagleBoard.org Debian Image 2015-03-01 Linux asdf 3.8.13-bone70 #1 SMP Fri Jan 23 02:15:42 UTC 2015 armv7l GNU/Linux gcc and g++ version 4.7.2 ~$ aplay -l **** List of PLAYBACK Hardware Devices **** card 1: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio] Subdevices: 0/1 Subdevice #0: subdevice #0 ~$ lsusb Bus 001 Device 004: ID 0ccd:0077 TerraTec Electronic GmbH Aureon Dual USB ~/jack2$ ./waf configure --alsa Setting top to : /home/debian/jack2 Setting out to : /home/debian/jack2/build Checking for 'g++' (C++ compiler) : /usr/bin/g++ Checking for 'gcc' (C compiler) : /usr/bin/gcc Linux detected Checking for program 'doxygen' : not found Checking for program 'pkg-config' : /usr/bin/pkg-config Checking for 'alsa' >= 1.0.18 : yes Checking for 'libffado' >= 1.999.17 : not found Checking for 'libfreebob' >= 1.0.0 : not found Checking for 'gtkIOStream' >= 1.4.0 : not found Checking for 'eigen3' >= 3.1.2 : not found Checking for header windows.h : not found Checking for 'portaudio-2.0' >= 19 : not found Checking for header mmsystem.h : no Checking for 'celt' >= 0.11.0 : not found Checking for 'celt' >= 0.8.0 : not found Checking for 'celt' >= 0.7.0 : not found Checking for 'celt' >= 0.5.0 : not found Checking for header opus/opus_custom.h : not found Checking for 'opus' >= 0.9.0 : not found Checking for 'samplerate' >= 0 : yes Checking for 'sndfile' >= 0 : yes Checking for library readline : yes Checking for header readline/readline.h : yes ================== JACK 1.9.11 svn revision will checked and eventually updated during build Build with a maximum of 64 JACK clients Build with a maximum of 768 ports per application Install prefix : /usr/local Library directory : /usr/local/lib Drivers directory : /usr/local/lib/jack Build debuggable binaries : no C compiler flags : ['-Wall'] C++ compiler flags : ['-Wall'] Linker flags : [] Build with engine profiling : no Build with 32/64 bits mixed mode : no Build standard JACK (jackd) : yes Build D-Bus JACK (jackdbus) : no Autostart method : classic Build doxygen documentation : no Enable ALSA driver : yes Enable FireWire driver (FFADO) : no Enable FreeBob driver : no Enable IIO driver : no Enable Portaudio driver : no Enable WinMME driver : no Build with CELT : no Build Opus netjack2 : no Build with libsamplerate : yes Build with libsndfile : yes Build with readline : yes ~$ tail /etc/security/limits.conf @audio - memlock 256000 @audio - rtprio 75 ~$ sudo jackd -P75 -dalsa -dhw:1,0 -p256 -n3 -r44100 -s & jackdmp 1.9.11 JACK server starting in realtime mode with priority 75 self-connect-mode is "Don't restrict self connect requests" creating alsa driver ... hw:1,0|hw:1,0|256|3|44100|0|0|nomon|swmeter|soft-mode|32bit configuring for 44100Hz, period = 256 frames (5.8 ms), buffer = 3 periods ALSA: final selected sample format for capture: 16bit little-endian ALSA: use 3 periods for capture ALSA: final selected sample format for playback: 16bit little-endian ALSA: use 3 periods for playback