|
JACK Transport
Many Linux audio applications branch from a fundamental UNIX
philosophy, and that is to "Write Programs that do one thing and do it
well". For this reason certain applications might focus on a
singular aspect of developing an audio project such as MIDI editing or
audio mixing. This approach has several benefits such as smaller
streamlined tools that can utilize less resources and subsequently
result in a system that is more responsive
to user interaction. Furthermore, system resources can be allocated to
user-made contents
rather than to application features that may not be applicable for a
certain project. The user also has the choice to only run those
applications that
are applicable to the current development phase of the project.
One of the obvious questions that arise from a system of this type is
how is
audio and data synced across all these different applications?
Most current Linux audio applications have the ability to communicate
with JACK by accepting data from JACK and transferring data to it.
Amongst the various uses of these data streams is the ability to unify
all audio application's transport controls to use JACK Transport
Controls.
What that means is that by setting up your audio applications to use
JACK Transport you are creating a unified transport interface for an
audio project across several different applications. For example,
clicking the Play button in an audio application set to use JACK
Transport Controls will move the Playhead in every audio application
using
JACK Transport to the current applications Playhead location and
play the audio project across all the linked applications in sync.
The procedure for setting an application to use JACK Transport
Controls varies from one application to the next, however each
application certainly emphasizes simplicity in setting up JACK
Transport, as you will see.
Modifying JACK's
Default Transport Setup
If you are running Ardour and Rosegarden, JACK will often try to
connect
Ardour's Transport Controls to Rosegarden, which may be useful if you
wish to use an external devices Hardware Transport Controls. If you
simply want to use
software to control the playback of your audio project, the following
method describes a setup for using JACK, Ardour, Rosegarden (with or
without external hardware and/or software midi) and Hydrogen together.
With
the preceding list of applications running, open JACK's Connections
Window.
Click the ALSA tab, select Ardour's "control"
Readable Client / Output Port and the Writable Client / Input Port that
it is connected to such as Rosegarden's "record in".
Click the
Disconnect button to disable this setup.
Set Audio Apps To Use
JACK Transport
1) Set Ardour to use JACK
Transport by clicking on the Positional
Sync
Source list at the top of the
main interface and set it to JACK.
2)
Set Rosegarden to use JACK Transport by opening the Configure
Rosegarden window, which is accessible through Edit >
Preferences. In the General Section, under the Behavior Tab click "Use
JACK transport" to activate this feature.
3)
Set Hydrogen to use JACK Transport by clicking the "J.TRANS" (Jack
Transport on-off) button in the main toolbar at the top of the window.
The button turns Blue
when it is ON.
Snapping in Ardour
Often you may want edits you make to an audio segment, such as cutting
a
segment or moving a segment, to snap to specific
intervals. This can easily be controlled in Ardour,
Click the Snap/Grid Mode list
in Ardour's main toolbar and
choose Grid.
Then specify intervals to snap to with the Snap/Grid Units
list.
Gain Automation in
Ardour
You can
control a track segments Gain properties with the Draw Gain Automation
tool, which can be found in Ardour's main toolbar.
Simply
clicking on a track segment will
add a node which can be moved around, restrictively, by means of the
snapping
options previously setup.
To delete
a node Shift-Right-Click
the Node.
You can
also Shift-Right-Click a marker
to delete it (regardless of your tool selection).
Program Changes in
Rosegarden
Sometimes you might need the convenience of changing a drum kit or
other midi device from one sound to another. If the effect is subtle it
probably won't warrant setting up another track and linking it to
another of the midi device's channels for a brief interlude. In this
case you might require a simple Program Change. The convenience of a
Program change (or other Midi Event)
is that it is intrinsically linked to a track segment, and not the
track itself.
1) In
Rosegarden
select the track segment where you would like the Program change to
occur. It's best to only have a single track
segment selected before proceeding.
2) With
the
track
segment
selected
click
the
Open Event List Editor
button in the main toolbar. If you have multiple track segments
selected Rosegarden will open a separate Event List Editor window for
each selected segment.
3) In
the
Event
List
Editor
select
the
location you would like the
Program change to occur, then click the Insert Event button (which has
a
star shaped icon).
4) The
resulting
dialog
box
allows
you
to
send various midi events to the midi device that
effects your current track segment selection. These events can be
controller events, pitchbend, system
exclusive and many other event types. In the Event Type list you will
find the option to insert a programchange.
Use
this
option
in
conjunction
with
the
Program
Change number to
specify another midi device sound.
|
|
