Qtractor An Audio/MIDI multi-track sequencer

[Intro] [Screenshots] [Requirements] [Downloads] [CVS] [Installation] [Configuration] [Bugs] [Support] [Acknowledgments]

What's Qtractor ?

Qtractor is an Audio/MIDI multi-track sequencer application written in C++ around the Qt4 toolkit.

The initial target platform will be Linux, where the Jack Audio Connection Kit (JACK) for audio, and the Advanced Linux Sound Architecture (ALSA) for MIDI, are the main infrastructures to evolve as a fairly-featured Linux Desktop Audio Workstation GUI, specially dedicated to the personal home-studio.

Licence: GNU General Public License (GPL)

Sourceforge project page: http://sourceforge.net/projects/qtractor

Screenshots

Click on image to see more screenshots...

Requirements

The software requirements for build and runtime are listed as follows:

Mandatory:

• Qt 4 (core, gui, xml), C++ class library and tools for crossplatform development and internationalization
  http://www.trolltech.org/products/qt/
• JACK Audio Connection Kit
  http://jackaudio.org/
• ALSA, Advanced Linux Sound Architecture
  http://www.alsa-project.org/
• libsndfile, C library for reading and writing files containing sampled sound
  http://www.mega-nerd.com/libsndfile/
• LADSPA, Linux Audio Developer's Simple Plugin API
  http://www.ladspa.org/

Optional (opted-in at build time):

• libvorbis (enc, file), Ogg Vorbis audio compression
  http://xiph.org/vorbis/
• libmad, High-quality MPEG audio decoder
  http://www.underbit.com/products/mad/
• libsamplerate, The secret rabbit code, C library for audio sample rate conversion
  http://www.mega-nerd.com/SRC/
• librubberband, Rubber Band Audio Time Stretcher,
  an audio time-stretching and pitch-shifting library
  http://breakfastquay.com/rubberband/
• liblo, Lightweight OSC implementation
  (needed for DSSI GUI support)
  http://liblo.sourceforge.net/
• DSSI, An API for soft synth plugins with custom user interfaces
  http://dssi.sourceforge.net/
• VST SDK, Steinberg's Virtual Studio Technology
  http://www.steinberg.net/

Downloads

Qtractor's still in some alpha stage of development, but already functional. The bleeding-edge development source tree is readily available from the sourceforge's public CVS repository. However there has been several so called pre-releases that might be representative of the project's shallowed milestones.

Latest release

2008-05-02 - The Frugal Damsel.
qtractor-0.1.3.tar.gz (user manual)

• As one may find convenient sometimes, the global time display format (frames, time or BBT) may now be changed on the main transport time spin-box context menu.
• Left-clicking on the track list number column now toggles all track content clip selection.
• Prevent audio-buffer initialization mashups when editing short audio clips while playback is rolling and within clip region.
• Audio peak files gets a bit simplified, dropping the peak frame count from its header; peak waveform graphics are now rendered as straight lines when over the end of audio file.
• The drop-span option (View/Options.../Drop multiple audio files into the same track) now also applies when importing tracks (as in Track/Import Tracks/Audio...) to concatenate multiple audio clips into one and the same new track.
• Audio and MIDI meter level colors are now user configurable (as global configuration options, View/Options.../Display/Meters)
• First attempt for Qt4.4 build support, regarding the bundled atomic primitives, which have changed upstream as advertised (thanks to Paul Thomas, for spotting this one first time).
• Record monitor switch is now an accessible button option on all track mixer strips; for visual consistency, the old bus "thru" switch button has been renamed to "monitor".
• Force track-view position reset to origin on session close.
• Fixed segfault on inserting an external file into files widget.
• Mixer splitter sizes are now better saved/restored when closed.
• Track record monitoring is now a state option, being toggled from the Track/State/Monitor menu; applies both to audio end MIDI tracks: when set all input will be pass-through to the current assigned output bus, including track plug-ins chain.
• Session dialog gets split in its own tab components, between descriptive, time and view configuration ones.
• Drifting correction among audio and MIDI engines is now back, but avoided while recording or should it be while looping? (EXPERIMENTAL REGRESSION)
• Time-stretching percent value gets its semantics inverted, as thought consistent with ones general sense for relative stretching ie., lower to shrink and higher to make longer. this is a major up-side-down change and should affect all sessions saved with time-stretched audio clips.
• Slack space in main tracks and MIDI clip editor views are now proportional to viewport width, leaving enough room for drag and moving content past the current session length, specially at the lower zoom levels.
• Clip end time is now also shown on tool-tip.
• When armed for recording, MIDI tracks are now monitored and filtered through their own output bus, thus having the same behavior as audio tracks; this also implies that all record armed tracks won't playback their current content material when recording is engaged and rolling; track mute and solo states are now honored on record monitoring.
• Audio clip pitch-shifting makes its first appearance, with the optional help from Chris Cannam's RubberBand library.
• A new MIDI editor tool is available: note/pitch randomize.
• Avoid (re)setting the default session directory if a session cannot be open or loaded for some reason.
• Another nastiness bites the dust: a subtle but progressive drifting has been swept away from the audio buffer looping; zero buffer flushing is now also taken into account, which was the cause for serious drifting on time-stretched clips.
• A major digital audio processing bug was tamed: audio clip fade-in/outs are now linearly piece-wise applied, even at the clip edges, giving a much smoother rendering and thus mitigating the nasty click-and-pop artifacts that were in fact due to some early design optimization with a poor and sloppy implementation.

Previous and older pre-releases, including the change log, are also available here.

Installation

The installation procedure follows the standard for source distributions. Once under the extracted source directory:

./configure [--prefix=prefix]
make

and optionally as root:

make install

This procedure will end installing the following couple of files:

• prefix/bin/qtractor
• prefix/share/pixmaps/qtractor.png
• prefix/share/applications/qtractor.desktop

Just launch prefix/bin/qtractor and you're off (hopefully). Note that the default installation path prefix is /usr/local .

Configuration

Qtractor holds its settings and configuration state per user, in a file located as $HOME/.config/rncbc.org/Qtractor.conf. Normally, there's no need to edit this file, as it is recreated and rewritten everytime qtractor is run.

Bugs

Plenty still, after all this is early alpha software ;).

Support

Qtractor is open source free software. For bug reports, feature requests, discussion forums, mailling lists, or any other matter related to the development of this piece of software, please use the Sourceforge project page.

You can also find timely and closer contact information on my personal web site.

Acknowledgments

Qtractor user manual has been co-authored by James Laco Hines.

Qtractor logo/icon is an original work of Andy Fitzsimon, borrowed from the public domain openclipart.org gallery.

This project has also a freshmeat.net entry.

Enjoy,

rncbc aka Rui Nuno Capela
rncbc at rncbc dot org