T = Tip
E = Explanation
A = Answer
T: You don't need a Realtime (RT) kernel, nor the RT option in JACK, to carry out simple audio tasks such as editing single files or recording a few tracks, or even sequencing an entire drum track with Hydrogen minus effects (you can use bare ALSA without JACK too).
Application or Realtime not working
E: Realtime is now granted on a per-group or per-user basis via Pam Security. The older, deprecated (to an extent) realtime-lsm method is no longer encouraged.
A: Ensure that you have a login manager like KDM, GDM, XDM or Slim. NEVER start JACK or QJackCtl as root. The group or user privileges are handled by the file /etc/security/limits.conf.
Notes are higher by at least half a tone
E: This is caused by resampling. Depending on hardware, you will get mixed results from loading a 44100Hz sample into a 48000Hz project. You have to understand the process of up/downsampling, take a look here.
A: Stick to a uniform sample rate, most commonly 44.1KHz. This is to nullify the effects of bad sample rate conversion. If you have to work on a project with a higher rate, pre-convert the samples; before you start working with them. Sometimes, you may have to set the rate on a per-application basis even if JACK is handling the communication. Check the settings of your program if that is the case.
T: You can use a shell script along with a multimedia editing tool to resample files in a given directory. Copy and paste the following in a terminal:
Code: Select all
wget -O resample.sh http://rafb.net/p/KklzsX52.txt
install -m755 resample.sh /usr/local/bin/resample