Effects

[Joery-M]

This document explains what 'effects' represent in the application.

Effects are modules that are added to timeline items (#290) to alter rendering and behavior of said items.

Effects can be grouped into the following groups:

• Transform
• Generate
• Transition
• Modify
• Audio
• Source

This list is subject to change with new features and should only be maintained as a baseline.

Effect types

Transform

This effect type transforms the existing image. For example moving the image to the right by 10 pixels.

Generate

This effect type generates an overlay on top of the existing image. For example:

• Text
• Outlines
• Fake lens flares

Transition

This effect type manages a transition between 2 timeline items. It should be visible on the timeline.
Examples:

• Cross-fade (audio and video)
• Slide
• Wipe

Modify

Name needs to change, this is very broad.

This effect type modifies the existing image or audio. So basically everything that doesn't fall into other categories.

Audio

This effect type specifically applies to audio, for example:

• Volume
• Normalize
• Panning
• Reverb

Source

This effect type generates the source data that will be used on the timeline item. There can only be 1 video source for each timeline item.
For video, the effect defines the base width and height and will provide the base image that will be used.
Examples:

• Media files
• SVG
• Static color
• External timeline
• Audio tone
• MIDI
• Subtitle file (VTT, SRT)
  For video, if there is no source to define width and height, the width and height of the current timeline should be used.

The source effect should also pass the following information to the timeline item:

• Source name
• Source type to be used for timeline colors
• Source duration
• (Video) Frame width and height

Implementation

Images

Image effects use a pipeline system of transformations. Each effect is added to an instance of Daguerreo, after which each one will sequentially modify the image.

A source effects starts the pipeline off by providing a CanvasRenderingContext2D, after which each transform effect will modify the source ctx.

Each effect passes along additional data like a DOMMatrix (or equivalent library), opacity and composite mode.

Audio

Audio effects use the Web Audio API to create AudioNode instances that alter audio.
Audio effects are instantiated with extra data like channel count and the BaseAudioContext.

Note

Audio is not implemented, and I (@Joery-M) need more experience with WebAudio to write a definitive reference.