Add speed

server-plugins/apply.js

@@ -4,12 +4,14 @@ import { SplitRenderPlugin } from './split-render.js';
 import { FramesPlugin } from './frames.js';
 import { CaptionPlugin } from './generate-captions.js';
 import { FlattenPathsPlugin } from './flatten-paths.js';
+import { SpeedPlugin } from './speed.js';
 
 const pluginRegistry = {
   'split-media-render': SplitRenderPlugin,
   'frames': FramesPlugin,
   'generate-captions': CaptionPlugin,
   'flatten-paths': FlattenPathsPlugin,
+  'speed': SpeedPlugin,
 };
 
 export async function applyPluginsPrerender(plugins, originalManuscript, originalManuscriptPath, jobId) {

server-plugins/speed.js

@@ -0,0 +1,55 @@
+import _ from 'lodash'
+import fs from 'fs'
+import { Plugin } from './plugin.js';
+import { FFMpegUtils } from 'common-utils';
+
+export class SpeedPlugin extends Plugin {
+  constructor(name, options) {
+    super(name, options);
+  }
+
+  async applyPrerender(originalManuscript, jobId) {
+
+  }
+
+  async applyPostrender(originalManuscript, jobId, outFiles) {
+    for (let outFile of outFiles) {
+      const speedFactor = this.options.speed || 1.0;
+      if (speedFactor !== 1.0) {
+
+        const tempFile = outFile + '.original.mp4';
+        fs.renameSync(outFile, tempFile);
+        try {
+          const pts = 1.0 / speedFactor;
+          if (pts <= 0) {
+            return
+          }
+
+          // atempo only supports 0.5-2.0, so we chain filters to approximate the target
+          let remaining = speedFactor;
+          const atempoFilters = [];
+          while (remaining > 2.0) {
+            atempoFilters.push('atempo=2.0');
+            remaining /= 2.0;
+          }
+          while (remaining < 0.5) {
+            atempoFilters.push('atempo=0.5');
+            remaining *= 2.0;
+          }
+          atempoFilters.push(`atempo=${remaining.toFixed(6)}`);
+          const audioFilter = atempoFilters.join(',');
+          this.log(`Speeding the video ${outFile} by a factor of x${speedFactor}`);
+          const cmd = `ffmpeg -i ${tempFile} -filter_complex "[0:v]setpts=${pts.toFixed(6)}*PTS[v];[0:a]${audioFilter}[a]" -map "[v]" -map "[a]" ${outFile}`;
+          await FFMpegUtils.execute(cmd);
+          fs.unlinkSync(tempFile);
+        } catch (err) {
+          this.log(`Error applying speed change: ${err}`);
+          if (fs.existsSync(outFile)) {
+            fs.unlinkSync(outFile);
+          }
+          fs.renameSync(tempFile, outFile);
+        }
+      }
+    }
+  }
+}