Trying to apply a watermark in real time with Node.js + FFMPEG - node.js

Question

I'm trying to write a streaming video server using Node.js express. the main task of the video server is to apply a watermark on the video. Here is my code
const express = require("express");
const fs = require("fs");
const path = require("path");
const ffmpeg = require("fluent-ffmpeg");
const ffmpegInstaller = require("#ffmpeg-installer/ffmpeg");
ffmpeg.setFfmpegPath(ffmpegInstaller.path);
const app = express();
app.get("/", function (req, res) {
const path = req.query.video;
const WATERMARK_PATH = req.query.id + `.png`;
const stat = fs.statSync(path);
const fileSize = stat.size;
const range = req.headers.range;
if (range) {
const parts = range.replace(/bytes=/, "").split("-");
const start = parseInt(parts[0], 10);
const end = parts[1] ? parseInt(parts[1], 10) : fileSize - 1;
const chunksize = end - start + 1;
const head = {
"Content-Range": `bytes ${start}-${end}/${fileSize}`,
"Accept-Ranges": "bytes",
"Content-Length": chunksize,
"Content-Type": "video/mp4",
};
res.writeHead(206, head);
new ffmpeg(fs.createReadStream(path, { start, end }))
.input(WATERMARK_PATH)
.complexFilter(
"overlay='x=if(eq(mod(n\\,18)\\,0)\\,sin(random(1))*w\\,x):y=if(eq(mod(n\\,18)\\,0)\\,sin(random(1))*h\\,y)'",
)
.outputOptions("-movflags frag_keyframe+empty_moov")
.toFormat("mp4")
.pipe(res, { end: true });
} else {
const head = {
"Content-Length": fileSize,
"Content-Type": "video/mp4",
};
res.writeHead(200, head);
new ffmpeg(fs.createReadStream(path))
.input(WATERMARK_PATH)
.complexFilter(
"overlay='x=if(eq(mod(n\\,18)\\,0)\\,sin(random(1))*w\\,x):y=if(eq(mod(n\\,18)\\,0)\\,sin(random(1))*h\\,y)'",
)
.outputOptions("-movflags frag_keyframe+empty_moov")
.toFormat("mp4")
.pipe(res, { end: true });
// fs.createReadStream(path).pipe(res)
}
});
app.listen(3020, function () {
console.log("App is running on port 3020");
});
As a result, the video doesn't play, and the following error appears in the console.
Error:
c:\myapp>node server.js
App is running on port 3000
events.js:292
throw er; // Unhandled 'error' event
^
Error: Output stream closed
at Timeout._onTimeout (c:\myapp\node_modules\fluent-ffmpeg\lib\processor.js:491:25)
at listOnTimeout (internal/timers.js:549:17)
at processTimers (internal/timers.js:492:7)
Emitted 'error' event on FfmpegCommand instance at:
at emitEnd (c:\myapp\node_modules\fluent-ffmpeg\lib\processor.js:424:16)
at Timeout._onTimeout (c:\myapp\node_modules\fluent-ffmpeg\lib\processor.js:491:17)
at listOnTimeout (internal/timers.js:549:17)
at processTimers (internal/timers.js:492:7)
If you remove the assignment of headers and contact the server, we will download the video, that is, FFMPEG works, a watermark is added.
Q: How do I set up video playback?