createThumbnail.js

const ffmpeg = require('fluent-ffmpeg');
const path = require('path');
const fs = require('fs');

// Function to maintain aspect ratio
function maintainAspectRatio(height, aspectRatio = 16 / 9) {
  const width = Math.round(height * aspectRatio);
  return `${width}:${height}`;
}

const aspectRatioSize = maintainAspectRatio(360);

// Function to detect scene changes and create a thumbnail
function detectScenesAndCreateThumbnail(inputVideoPath, outputThumbnailPath) {

  return new Promise((resolve, reject) => {
  const tempSceneFilePath = path.resolve(`scenes_${path.basename(inputVideoPath, '.mp4')}.txt`);

  ffmpeg(inputVideoPath)
    .outputOptions([
      '-vf', 'select=gt(scene\\,0.3),metadata=print:key=lavfi.scene_score', // Detect scene changes
      '-vsync', 'vfr',
      '-f', 'null'
    ])
    .on('start', function(commandLine) {
      console.log(`Spawned FFmpeg with command: ${commandLine}`);
    })
    .on('stderr', function(stderrLine) {
      fs.appendFileSync(tempSceneFilePath, stderrLine);
    })
    .on('end', function() {
      fs.readFile(tempSceneFilePath, 'utf8', (err, data) => {
        if (err) {
          createThumbnail(inputVideoPath, outputThumbnailPath, true); // Fallback to simple thumbnail
        } else {
          const hasSceneChanges = data.includes('scene_score');
          createThumbnail(inputVideoPath, outputThumbnailPath, !hasSceneChanges);
          resolve();
        }
        fs.unlink(tempSceneFilePath, () => {}); // Clean up temporary file
       
      });
    })
    .on('error', function(err) {
      createThumbnail(inputVideoPath, outputThumbnailPath, true); // Fallback to simple thumbnail
    })
    .saveToFile('/dev/null'); // Specify a dummy output to satisfy ffmpeg requirements
  })
}

// Function to create a thumbnail
function createThumbnail(inputVideoPath, outputThumbnailPath, fallback = false) {
  return new Promise((resolve,reject)=>{

  const vfFilter = fallback 
    ? `thumbnail,scale=${aspectRatioSize}` 
    : `select=gt(scene\\,0.3),scale=${aspectRatioSize}`;

  ffmpeg(inputVideoPath)
    .outputOptions([
      '-vf', vfFilter, // Scene detection and scaling or fallback
      '-frames:v', '1', // Extract one frame
      '-vsync', 'vfr' // Variable frame rate to handle selected frames
    ])
    .on('end', () => {
      console.log(`Thumbnail for ${path.basename(inputVideoPath)} extracted successfully`);
      resolve();
    })
    .on('error', (err) => {
      if (!fallback) {
        console.log(`Scene detection failed for ${path.basename(inputVideoPath)}, retrying with thumbnail filter...`);
        createThumbnail(inputVideoPath, outputThumbnailPath, true);
      } else {
        reject();
        console.error(`Error extracting thumbnail for ${path.basename(inputVideoPath)}:`, err.message);
      }
    })
    .save(outputThumbnailPath);
  })
}

// Loop through the videos
const thumbnailCreator = async (videoFilePath,thumbnailFilePath)=>{
  const inputVideoPath = path.resolve(videoFilePath);
  const outputThumbnailPath = path.resolve(thumbnailFilePath);
  try{
    await detectScenesAndCreateThumbnail(inputVideoPath, outputThumbnailPath);
  }
  catch(err){
    logger.error(`Error extracting thumbnail for ${videoFilePath}`);
    logger.error(JSON.stringify(err));
  }
  
}

module.exports = thumbnailCreator;