xfade.lv2 is an audio-plugin for stereo cross-fading 2 x 2 input channels to 2 output channels.

Compiling this plugin requires LV2 SDK, gnu-make and a c-compiler.

  git clone https://github.com/x42/xfade.lv2.git
  cd xfade.lv2
  make
  sudo make install PREFIX=/usr

  # test run
  jalv.gtk http://gareus.org/oss/lv2/xfade

Note to packagers: The Makefile honors PREFIX and DESTDIR variables as well as CFLAGS, LDFLAGS and OPTIMIZATIONS (additions to CFLAGS).

The plugin has 3 parameters which are interpolated and can be operated in realtime without introducing clicks or similar effects.

Fade between Input A (left-end, -1.0) and Input B (right-end, +1.0).

Allows to smoothly choose the A/B behaviour:

• Linear (default): constant Amplitude. Out ∝ InA + InB
• Equal Power: retain signal power. Out² ∝ InA² + InB²

• X-fade (default): Inputs are fade over the complete range of the Signal A/B control range.
• V-fade: Input A is only faded if Signal A/B is > 0.0, Input B if Signal A/B < 0.0

Consider the following simple diagrams:

     Vol
      ^
  1.0 |AA           BB
      |   A       B
      |     A   B          +-------------+
      |       X            | X-fade mode |
      |     B   A          +-------------+
      |   B       A
  0.0 |BB           AA
      +-----------------> (A/B control)
       -1     0     +1



     Vol
      ^
  1.0 |AAAAAAAXBBBBBBB
      |      B A
      |     B   A          +-------------+
      |    B     A         | V-fade mode |
      |   B       A        +-------------+
      |  B         A
  0.0 |BB           AA
      +-----------------> (A/B control)
       -1     0     +1

xfade.lv2 running in jalv.gtk:

With Ardour3, use a 4 channel bus, bypass the VBAP-pan control and only connect Bus outputs 1&2 to the master bus: