Proposal Crossfade

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Revision as of 22:36, 17 April 2008 by Jeff Hussmann (talk | contribs)
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  • Display - The original mock-up is only effective at displaying a crossfade if a single linked fade that lasts the entire duration of the overlapping region is being displayed.
    • Single linked fade
    • Indicating Clip Overlap Regions
      • Zoomed Out - What does this text look like?
    • Single fade vs. Independent Fade

  • Summary

I want to build an intuitive interface for creating non-destructive cross-fades in Audacity.

Here is a link to the origin project suggestion on the Audacity GSoC ideas page. GSoC_Ideas#Intuitive_cross-fading

    • Stage 1 - half way target deliverables
    • end of summer deliverables
  • Proposal

For the first stage of the project, I will implement the basic functionality implied by the the cross-fade mockup at

  • Cross-fade functionality - For this stage of the project, the fade-in and fade-out shapes will be a single linked fade. Three fade shapes will be selectable.
    • Linear - A constant-gain cross fade in which a linear envelope decreasing from 1 to 0 over the course of the fade is applied to the left-hand clip and a linear envelope increasing from 0 to 1 is applied to the right-hand clip.
    • Logarithmic - A constant-power cross fade in which a logarithmically decreasing envelope is applied to the left-hand clip and the mirror image of this envelope is applied to the right-hand clip.
    • S-Curve - A commonly discussed fade shape - see for instance An envelope of 1/2+1/2 cos (2*pi*w/T) is applied to the left-hand clip where w is the number of samples from the start of the fade and T is the fade length in samples. The mirror image of this envelope is applied to the right-hand clip.
  • Display -

When a modifier is held down (I propose ctrl-shift), clips dragged near each other will no longer snap

    • draft gui images
      • zoomed in view
      • zoomed out view
    • define keystrokes and behavior


    • define mouse behavior
    • undo-stack
    • stereo track support
      • display different from mono tracks
    • crossfade type:
      • constant amplitude cross-fade
      • constant sum power cross-fade
      • fade-out-and-back-again "crossfade"
      • picker for fade type
    • presets / repeat effect (having done one cross fade, do the next one with the same 'parameters')
    • files/classes affected
      • planned changes to affected files

  • possible optional extensions
    • fade in/out with out another clip