- 1 Concept
- 2 Jack Draft
- 3 Other Stuff
Concept of wiki documentation accompanying infrastructure and audio applications that are present in binary or source form in the official arch repositories, in AUR and in the archaudio.org repository.
Due to limited workforce documentation focus should be on:
- Base audio system (jack et. al.)
- applications present in the official binary repo
- applications present in the archaudio.org binary repo
- applications present in the archaudio.org source repo
- applications present in AUR
Organisation of information through use of categorization as tagging system (multiple categories per article describing the basic functionality) and extensive use of hyperlinks between articles in the wiki as well as to external pages like manuals and tutorials.
- Some kind of portal, replacement for the proaudio page, reuse content if possible
- tagging structure (categories)
- Infrastructure: jack, alsa, midi (jackmidi, alsamidi ?)
- plugin APIs: ladspa, dssi, lv2, (vst-native, vst-windows?),
- kind of application: sequencer, plugin host, synth, ..
- ... what else and what exactly?
- One page per application (at least for core applications)
- link to homepage, manual, tutorials..
- own manual/tutorial if external information insufficient
- arch specific information
- "What needs to be done?"-page
Part One: Beginners Guide
Who is this Jack? Do I need him?
If all you want to do is listen to music and watch videos you don't need it. It could get into the way or could be useful for special tasks, it all depends on your exact usecase.
Jack is designed with two goals in mind: low-latency and flexible connections.
- Low-latency is especially useful in professional-grade recording applications, to be able to hear what you play or hear without noticeable delay. In this respect jack performs at least as well as similar systems on other operatingsystems.
- Flexible connections is an outstanding possibility that only jack provides. It allows you to route audio output from one application to another to three others to the next two back to anotherone, record it with yet another one and to your speakers. Or so, or any other way you can imagine.
So do you need jack? If you plan on Linux in a recording or audio production environment, be it a professional grade studio or your bedroom, you almost certainly need it to achieve lowest possible latencies and make full use of the available applications. Also the connection possibilities make it a very useful component in many special applications, be it a complicated multi-speaker setup or just for adding some compression and room equalisation when watching movies. The possibilities are there, pretty much all you need is your imagination.
Show and explain how to get a basic setup that should work for most users. On commandline and in qjackctl
How to make connections in qjackctl -> connect and in patchage (maybe even brief example on commandline)
What are they? (Why didn't I have them on Windows/OSX?) What can I do to get rid of them?
Xruns are either buffer-over or buffer-underruns, so basically some part of your audio chain couldn't keep up and data got lost. It's therefor quite essential to avoid them.
You used audio applications on Windows or OSX and never heard of something like that? Be assured that this problem exists there as well, the applications there often just don't tell you what's going on, you just end up with crackling noises in your recordings.
So how do you avoid them? There are many things that can cause them or influence their occurence which in concequence means that there are many things you can try.
Part Two: Additional Information
List of content without order:
- devices by alphanumeric name, cat /proc/asound/cards
0 [UA25 ]: USB-Audio - UA-25 EDIROL UA-25 at usb-0000:00:10.0-2, full speed
the thing in brackets -> UA25 or try 'aplay -l',
- performance tweaks (move these to a dedicated audio system tweaks page?)
- usage tricks
- killing qjackctl without killing jack (move to qjackctl page?)
- killall qjackctl
- start jack before qjackctl
- killing qjackctl without killing jack (move to qjackctl page?)
- additional hardware latency compensation: -I and -O in frames
- per application portlimit (256, needs change in source)
- jack with dbus and implications
- dbus applications, jack_control
- "JACK_NO_START_SERVER" env variable
timers, hpet, hrtimer
hpet is a very high precission timer available for newer motherboards. Using it might enable better midi timing than using older timers. Jackd can use hpet if run with the options '-c h', but it's not totally clear to me if this improves midi timing and in which cases it improves it.
I couldn't test it since I still have troubles.
How to check whether hpet is available: $ ls -l /dev/hpet crw-rw---- 1 root root 10, 228 2009-11-10 10:13 /dev/hpet
It seems like you have hpet, but it's not a certainty. I got this through adding hpet=force to the kernel command line:
$ dmesg | grep -i hpet Kernel command line: root=/dev/disk/by-uuid/3e47466f-5ca1-499b-85fc-152074f36364 ro hpet=force pci 0000:00:11.0: Failed to force enable HPET
As you can see, it failed, so hpet isn't available, yet I have /dev/hpet.
I recommend to try: $ dmesg | grep -i hpet
If hpet isn't enabled it will tell you. If you don't have a BIOS option to enable it, you could try hpet=force, but chances are your mainboard just doesn't have it, as in my case.
/dev/hpet is a userspace interface to hpet, only jack uses it. If you run jack with the option '-c h' you might get a message saying: This system has no accessible HPET device (Permission Denied)
Which means you need to change the ownership group of /dev/hpet to audio: (sudo) chgrp audio /dev/hpet
If jack still complains and says: This system has no accessible HPET device (Device or resource busy)
Something is still wrong..
check whether alsa uses hrtimer as default source: $ zgrep CONFIG_SND_SEQ_HRTIMER_DEFAULT /proc/config.gz CONFIG_SND_SEQ_HRTIMER_DEFAULT=y
This annoys me a lot, and seems to even cause xruns, at least on my laptop. Here's a good resource I found on this: http://www.shallowsky.com/linux/x-screen-blanking.html Theoretically the manpage should help:
However, the syntax is rather strange. This is more or less what should keep the screen from turning off:
xset s off xset 0 0 0 xset -dpms
To query the status of xset:
These settings can be made permanently in xorg.conf, but don't ask me about the syntax. I don't use the xorg.conf and put it into xinit.rc. Actuall, these two lines are likely enough, but I didn't test it:
xset s off xset -dpms
Want To Know What's compiled Into Your Kernel?
zcat /proc/config.gz | $PAGER
zcat /proc/config.gz | grep ACL
Other useful stuff seems to be: zless/zmore
Apps that would be nice to have in AUR and archaudio.org
GUI version of some LV2 plugins - http://sourceforge.net/projects/teliasopia/
Very nice looking note visualization tool - http://clam-project.org/wiki/Chordata_tutorial
Musical midi accompainment - http://www.mellowood.ca/mma/
probably nice ladspa plugins - http://www.studionumbersix.com/foo/
some more new plugins - http://sourceforge.net/projects/pxu/
matrix jack connection manager, in early development afaik - http://svn.fuzzle.org/jsweeper/trunk/
genetic algorithm synthesizer, it looks fun - http://www.pawfal.org/Software/fastbreeder/
daw based on libardour - http://ayyi.org/
Rumors and stuff
ZynAddSubFX Qt GUI - http://metellius.mine.nu/zynexperimental.png