mqtt-explorer/scripts/cutVideoSegments.js

#!/usr/bin/env node

/**
 * Cut video into segments as GIFs based on scenes.json
 * 
 * This script reads scenes.json and uses ffmpeg to create GIF segments
 * from the ui-test.mp4 video file.
 */

const fs = require('fs');
const { spawn } = require('child_process');

// Check required files exist
if (!fs.existsSync('scenes.json')) {
  console.error('scenes.json not found');
  process.exit(1);
}

if (!fs.existsSync('ui-test.mp4')) {
  console.error('ui-test.mp4 not found');
  process.exit(1);
}

console.log('Cutting video into GIF segments based on scenes.json...');

const scenes = JSON.parse(fs.readFileSync('scenes.json', 'utf8'));

const GIF_SCALE = process.env.GIF_SCALE || '1024';

console.log('Creating GIF segments...');

// Sanitize scene name to prevent path traversal and command injection
function sanitizeName(name) {
  // Remove any characters that aren't alphanumeric, dash, or underscore
  return name.replace(/[^a-zA-Z0-9_-]/g, '-');
}

async function cutSegmentAsGif(scene, index) {
  const safeName = sanitizeName(scene.name);
  const segmentName = `segment-${String(index + 1).padStart(2, '0')}-${safeName}`;
  const paletteFile = `${segmentName}-palette.png`;
  const outputFile = `${segmentName}.gif`;
  const startTime = scene.start / 1000; // Convert ms to seconds
  const duration = scene.duration / 1000; // Convert ms to seconds
  
  console.log(`Creating ${outputFile} (start: ${startTime}s, duration: ${duration}s)`);
  
  // Step 1: Generate palette for this segment
  await new Promise((resolve, reject) => {
    const ffmpeg = spawn('ffmpeg', [
      '-y',
      '-ss', startTime.toString(),
      '-t', duration.toString(),
      '-i', 'ui-test.mp4',
      '-vf', `fps=10,scale=${GIF_SCALE}:-1:flags=lanczos,palettegen`,
      paletteFile
    ]);
    
    ffmpeg.on('close', (code) => {
      if (code === 0) {
        resolve();
      } else {
        console.error(`Failed to create palette for ${outputFile}`);
        reject(new Error(`ffmpeg palette generation exited with code ${code}`));
      }
    });
  });
  
  // Step 2: Create GIF using the palette
  await new Promise((resolve, reject) => {
    const ffmpeg = spawn('ffmpeg', [
      '-y',
      '-ss', startTime.toString(),
      '-t', duration.toString(),
      '-i', 'ui-test.mp4',
      '-i', paletteFile,
      '-filter_complex', `fps=10,scale=${GIF_SCALE}:-1:flags=lanczos[x];[x][1:v]paletteuse`,
      outputFile
    ]);
    
    ffmpeg.on('close', (code) => {
      // Clean up palette file
      try {
        fs.unlinkSync(paletteFile);
      } catch (e) {
        // Ignore cleanup errors
      }
      
      if (code === 0) {
        resolve();
      } else {
        console.error(`Failed to create ${outputFile}`);
        reject(new Error(`ffmpeg GIF creation exited with code ${code}`));
      }
    });
  });
}

(async () => {
  for (let i = 0; i < scenes.length; i++) {
    await cutSegmentAsGif(scenes[i], i);
  }
  console.log('Video segments created successfully');
})().catch(err => {
  console.error(err);
  process.exit(1);
});