readme.md

Instructions to repro

create both the files, index.js and worker.js

change the file name in index.js as required with any video file you want

change the storage folder as well if you want

change FFMPEG_PATH and FFPROBE_PATH in worker.js to the path you have in your system idk

npm i fluent-ffmpeg

node index.js

expected out put

Percentage processing: 10%
Generating screenshots for job#test
Percentage processing: 20%
Percentage processing: 30%
Percentage processing: 40%
Percentage processing: 50%
Percentage processing: 60%
Percentage processing: 70%
Percentage processing: 80%
Percentage processing: 90%
Percentage processing: 100%
[
  'F:\\TempEncoderStorage\\screenshot-test-10.png',       
  'F:\\TempEncoderStorage\\screenshot-test-20.png',       
  'F:\\TempEncoderStorage\\screenshot-test-30.png',       
  'F:\\TempEncoderStorage\\screenshot-test-40.png',       
  'F:\\TempEncoderStorage\\screenshot-test-50.png',       
  'F:\\TempEncoderStorage\\screenshot-test-60.png',       
  'F:\\TempEncoderStorage\\screenshot-test-70.png',       
  'F:\\TempEncoderStorage\\screenshot-test-80.png',       
  'F:\\TempEncoderStorage\\screenshot-test-90.png',       
  'F:\\TempEncoderStorage\\screenshot-test-100.png'       
]

actual output

Percentage processing: 10%
Generating screenshots for job#test
Percentage processing: 20%
Percentage processing: 30%
Percentage processing: 40%
Percentage processing: 50%
Percentage processing: 60%
Percentage processing: 70%
Percentage processing: 80%
Percentage processing: 90%
Percentage processing: 100%

It seems the parentPort.postMessage is never executed.

index.js

import { Worker } from "worker_threads";
function run() {
  const worker = new Worker("./worker.js", {
    workerData: {
      file: "E:\\TV Series\\Hyouka (720p)\\01 - The Revival of the Long-established Classic Literature Club.mkv",
      storageFolder: "F:\\TempEncoderStorage"
    }
  });

  worker.on("message", (message) => console.log(message));
}

run();

worker.js

const { parentPort, isMainThread, workerData } = require("worker_threads");
const Ffmpeg = require("fluent-ffmpeg");
process.env.FFPROBE_PATH="H:\\ffmpeg-20200617-0b3bd00-win64-static\\bin\\ffprobe.exe"
process.env.FFMPEG_PATH="H:\\ffmpeg-20200617-0b3bd00-win64-static\\bin\\ffmpeg.exe"

if(isMainThread) {
  process.exit();
}
const PERCENTAGE_INCREMENT = 10;

function execScreenshot(id, percentage) {
  return new Promise((resolve, reject) => {
    console.log(`Percentage processing: ${percentage}%`)
    if(percentage >= PERCENTAGE_INCREMENT * 10) {
      resolve(
        (new Array(10)).fill(0).map((v, k) => `${workerData.storageFolder}\\screenshot-${id}-${k + 1}0.png`)
      );
      return;
    }
  
    Ffmpeg(workerData.file)
      .on("start", () => percentage <= PERCENTAGE_INCREMENT && console.log(`Generating screenshots for job#${id}`))
      .on("error", (error, stdout, stderr) => {
        console.error(error, stdout, stderr);
        reject(error);
      })
      .on("end", (stdout, stderr) => {
        execScreenshot(id, percentage + PERCENTAGE_INCREMENT);
      })
      .takeScreenshots({
        filename: `screenshot-${id}-${percentage}.png`,
        folder: workerData.storageFolder,
        timemarks: [`${percentage}%`],
        count: 1
      }, workerData.storageFolder);
  })
}

async function threadRun() {
  try {
    execScreenshot("test", 10).then(data => parentPort.postMessage(data));
  } catch (e) {
    console.error(e);
  }
}
threadRun();