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Qtractor 0.4.6 - The Funky Deviless is here!

So much to tell, even more to do... then one could hardly shake, this long overdue. Lousy rhymes and no miserly times. And there it is: a bug-fix release, I'll mean to ease.

Oh crap! Let's get it through once and for all.

With huge compliments to all who got the nerve and report as many too much idiosyncrasies (nee bugs). Don't, never look back. There's plenty more ahead, no matter where you look, or hear, whether is up or down hill :)

Qtractor 0.4.6 (funky deviless) is here!

Release highlights:

  • MIDI Editor draw mode (aka paint mode) (NEW)
  • MIDI Swing-quantize (NEW)
  • LV2 UI Instance & Data-access extension support (NEW)
  • JACK Session support (EXPERIMENTAL) (NEW)
  • LV2 Save/Restore extension support (NEW)
  • MIDI Editor event list in-line editing (NEW)
  • MIDI Clip time-stretching (FIX)
  • MIDI Clip editor file salvage quietness (NEW)
  • MIDI Control bus switching crash (FIX)
  • MIDI Bank-selection backout (FIX)
  • Initial widget geometry extents (FIX)
  • Input-only bus playback crash (FIX)
  • Bus connection persistence crash (FIX)
  • Drag-and-drop cloning plugins (FIX)
  • MIDI Editor floating-selection persistence (NEW)
  • Audio inserts garbage signal (FIX)

A bit more or not so detailed change-log is found below.


Project page:


Weblog (upstream support; you're already reading it):

License (no kiddin'):

Qtractor is free, open-source software, distributed under the terms of the GNU General Public License (GPL) version 2 or later.


  • Introducing a non-painting edit sub-mode on the MIDI clip editor's piano-roll (see Edit/Select Mode/Edit Draw menu).
  • The MIDI clip editor (aka piano-roll) is now a lot more quiet about saving its own dirty content, delegating all
    salvage questions to main session control.
  • Don't show session restart message box when changing JACK transport mode option anymore.
  • Dedicated MIDI control bus switching fixed. Was closing the wrong bus eventually and crashing the whole show with it (fixes bug #2989590).
  • MIDI bank/program backout has been corrected on MIDI track properties dialog rejection (ie. user cancellation).
  • MIDI bank select method has been corrected for tracks with no instrument defined (probably fixing bug #2987071).
  • LV2 UI Instance and Data Access extension support added; reduce LV2 external UI parameter value update flickering.
  • JACK session infrastructure support. (EXPERIMENTAL)
  • Initial widget geometry and visibility persistence logic has been slightly revised as much to avoid crash failures
    due to wrong main widget hidden state.
  • Initial mixer widget extents are now set reasonably larger.
  • General source tree layout and build configuration change.
  • Ever since smooth-ramping introduction that having at least one input-only buses were causing immediate playback crashes, now hopefully fixed.
  • Refactored for common engine client nomenclature, primarily provided by JACK, then secondarily passed to ALSA Sequencer, getting rid of the JackUseExactName requirement and lifting the unique/single instance restriction in the process.
  • Current JACK Transport, MMC Device, and MIDI Song Position pointer (SPP) control modes are now saved/loaded as part of session option properties.
  • MIDI clip editor's context menu crash on Qt >= 4.6 has been fixed (resolving bug #2972603).
  • An ancient double-free corruption has been finally fixed at the audio/MIDI bus connection persistence logic.
  • Improved visibility of track state buttons text (R, M, S) when turned on dark colored themes.
  • LV2 Save/Restore extension support kicks off.
  • MIDI engine read-ahead period has been shortened to half than it was since inception--now it's a 500msec cycle.
  • MIDI clip editor event list gets its due inline editing, for time, note, value/velocity and duration columns, just
    one double-click away over the target cell ;)
  • Add-plugin selection dialog position and extent are now remembered across invocations and application sessions
    (tipping by Frank Neumann).
  • MIDI clip time-stretching is now made available through the same gestures as audio ones, by just shift+dragging
    either of the clip edges.
  • Drag-and-copying plug-in instances (cloning) is now fixed with regard to parameter value replication.
  • MIDI clip editor snap-per-beat setting is now independent from main multi-track view; File/Save As... dialog fixed;
    the current event selection is now kept floating as long as it's possible after editing command actions; finally,
    edit mode has been extended to free-hand event drawing, chalking off (piano roll) draw mode from the TODO list.
  • Swing-quantize has finally made its overdue debut as an additional MIDI clip editor tool (see Tools/Quantize...).
  • Almost since its inception, audio inserts were injecting garbage random noise when not being activated, now fixed.
  • Dedicated audio output ports for MIDI track plugins, now have their connection persistence back in business due on session load.

Cheers && Enjoy (what else?)


I tried it under Ubuntu 9.10 (from sources). Preferences dialog doesn't unblock OK button when something changed, though, it asks wether to apply changes or not.

rncbc's picture

Preferences dialog or is it File/Properties... dialog? This looks for essential session property that you must fill in no matter what: its name.


here fresh Ubuntu 10.04 install.... tried new qtracor version but buggy.... doesn't launch : segmentation error....

rncbc's picture

Can you try using gdb or strace and let it be known where or what precisely is crashing? Usual suspects are missing or bad libslv2 dependencies like librdf, librasqal or whatever ...

Please give more details about your system and installation.


I have a Ubuntu 10.04 newly installed.
Jack2. HDA Intel (or UA-25 usb)

libslv2 is installed and the other ones you mentionned as well...
In fact it is just that when I click on qtractor's icon, the interface appears during less than half a second and then vanishes...
All is working well if I reinstall the previous version of Qtractor.


rncbc's picture

I guess you've installed from one of the debs above...

Any chance in summoning the beast from source?


Sorry. I mean View/Options (by F12 key).

rncbc's picture

Ok. Please. check for invalid option values. Most specially some filenames (like New session template) that must exist, otherwise the OK button will stay grayed until you disable the offending option or set it a valid value (existing file).


Aaargh, sorry! I found a blocker. I switched FLAC 32-float sample format for export/capture functions. 8) So, may be, bug is that settings are saved when I say "Yes"? ;)
IMO, better behaviour is to not show sample format items, unavailable for selected file format.

Thanks very much for taking the trouble to provide us with .deb files, Rui. Sadly, I can't comment on your latest offering yet as, similar to a poster above, Qtractor folds on start up on my amd64 machine.

I ran it as root in the terminal and received (from memory only!) this output:-

[2] 2011
[1] Segmentation fault

if that's any help?

I guess this is the boring bit, especially when your 'testers' go into hysterics (me included!) the moment words like 'source' and 'dependencies' are mooted! ;-)

I admire your tenacity...


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