Jackd Raspberry Real Time Audio
UPDATE! Have a look to http://rpi.autostatic.com, instead, which should provide a fully working out of the box solution. Here they have jack, if you only need jack: http://downloads.autostatic.com/rpi/jackd2/ '
the start it with
jackd -d alsa -r 48000 -n 16
if you want to use the internal sound card. I can tell you that with the latest kernel, mmap patched, and the above compiled jack, on revision B, you'll get decent sounds even on the internal audio jack.
Raspberry PI is a very fun to use little linux box which runs debian out of the box and has a nice ARM processor without any fan. It costs less than 50€, has HDMI, USB, LAN SD-CARD storage. It also features an integrated audio output jack but... if you need real time audio for professional application you'll soon find out that it's garbage. However you can connect an external USB card to it and enjoy some good sounds. You know you'll need jack to stay away from pop and clicks in your music setup. Jack is available through raspberry pi repository. If - however - you compile it again, from sources, you'll find out that it works better. Here is my working compiled jack package. Have fun with it!
To download and install jack:
wget http://www.my-lab.it/pub/libjack-jackd2-0_1.9.8-1_armhf.deb sudo apt-get remove jackd* sudo dpkg -i libjack-jackd2-0_1.9.8-1_armhf.deb
Restore symlinks, not provided by this package
sudo su cd /usr/lib ln libjack.so.0.1.0 libjack.so.0 ln libjacknet.so.0.1.0 libjacknet.so.0 ln libjacknetserver.so.0.1.0 libjacknetserver.so.0 ln libjackserver.so.0.1.0 libjackserver.so.0
Remember to change group priorities before installing it (you'll need to reboot thereafter)
sudo echo "@audio - rtprio 99" >> /etc/security/limits.conf sudo echo "@audio - memlock unlimited" >> /etc/security/limits.conf sudo echo "@audio - nice -19" >> /etc/security/limits.conf
Then start jack with -p 16 to avoid bus errors
jackd -p 16 -d alsa -d hw:1,0
or, for better buffering
jackd -p 16 -d alsa -d hw:1,0 -s -p 8192
Remember to tweak usual stuff like dwc_otg.speed=1 in /boot/cmdline.txt and nrpacks=1 in /etc/modprobe.d/alsa-base.conf