add dummy transition

README.md

@@ -181,7 +181,7 @@ Edit specs are JavaScript / JSON objects describing the whole edit operation wit
 
 ### Transition types
 
-`transition.name` can be any of [gl-transitions](https://gl-transitions.com/gallery), or any of the following: `directional-left`, `directional-right`, `directional-up`, `directional-down` and `random`.
+`transition.name` can be any of [gl-transitions](https://gl-transitions.com/gallery), or any of the following: `directional-left`, `directional-right`, `directional-up`, `directional-down`, `random` or `dummy`.
 
 ### Layer types
 

examples/audio-transition.json5

@@ -23,9 +23,13 @@
       { type: 'title-background', text: 'Clip 4' },
       { type: 'audio', path: './assets/sample2.m4a' }
     ] },
-    { layers: [
+    { transition: { name: 'dummy' }, layers: [
       { type: 'title-background', text: 'Clip 5' },
       { type: 'audio', path: './assets/sample1.m4a' }
     ] },
+    { layers: [
+      { type: 'title-background', text: 'Clip 6' },
+      { type: 'audio', path: './assets/sample2.m4a' }
+    ] },
   ],
 }

index.js

@@ -152,7 +152,14 @@ const Editly = async (config = {}) => {
     return newAcc;
   }, 0);
 
-  const { runTransitionOnFrame } = GlTransitions({ width, height, channels });
+  const { runTransitionOnFrame: runGlTransitionOnFrame } = GlTransitions({ width, height, channels });
+
+  function runTransitionOnFrame({ fromFrame, toFrame, progress, transitionName, transitionParams }) {
+    // A dummy transition can be used to have an audio transition without a video transition
+    // (Note: You will lose a portion from both clips due to overlap)
+    if (transitionName === 'dummy') return progress > 0.5 ? toFrame : fromFrame;
+    return runGlTransitionOnFrame({ fromFrame, toFrame, progress, transitionName, transitionParams });
+  }
 
   function startFfmpegWriterProcess() {
     // https://superuser.com/questions/556029/how-do-i-convert-a-video-to-gif-using-ffmpeg-with-reasonable-quality