Turn Static Images into Seamless MJPEG Sequences

I recently embarked on a project to stream live DSLR footage to a website or app. My goal was simple: real-time image streaming from my DSLR. However, achieving seamless streaming proved more challenging than anticipated.

This is how I solved it, leveraging DigiCamControl and Express.js.

The Challenge

DigiCamControl is a fantastic tool for DSLR control and LiveView. The caveat? LiveView provides a static image, updating approximately 20 times per second upon reload. While functional, it's not a true real-time feed.

My objective was to transform this image stream into a standard MJPEG feed, compatible with web and desktop applications.

The Solution

Through experimentation, I discovered a method to convert these static images into a smooth MJPEG stream using Express.js. The process is surprisingly straightforward.

Here's the backend code:

<code class="language-javascript">const express = require('express');
const axios = require('axios');

const app = express();
const PORT = 3000; // MJPEG proxy port
const DIGICAM_URL = 'http://127.0.0.1:5513/liveview.jpg';
const FPS = 20; // Frames per second

app.get('/liveview.mjpeg', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'multipart/x-mixed-replace; boundary=frame',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive',
  });

  const interval = setInterval(async () => {
    try {
      const response = await axios.get(DIGICAM_URL, { responseType: 'arraybuffer' });
      const imageData = response.data;

      res.write(`--frame\r\n`);
      res.write(`Content-Type: image/jpeg\r\n\r\n`);
      res.write(imageData);
      res.write(`\r\n`);
    } catch (error) {
      console.error('Error fetching image:', error.message);
      clearInterval(interval);
      res.end();
    }
  }, 1000 / FPS);

  req.on('close', () => {
    clearInterval(interval);
  });
});

app.listen(PORT, () => {
  console.log(`MJPEG server running on http://localhost:${PORT}/liveview.mjpeg`);
});</code>

Addressing a Common Error

Initially, I encountered this error: Error fetching liveview image: connect ECONNREFUSED ::1:5513. This stemmed from how localhost resolves on certain systems. The solution was simple: replacing http://localhost:5513/liveview.jpg with http://127.0.0.1:5513/liveview.jpg.

The Result

With the server running, I successfully streamed the DSLR's LiveView feed to my web app at a smooth 20 FPS. While not as sophisticated as RTSP, this MJPEG approach is efficient for most applications.

If you're aiming to integrate a live DSLR feed into your project, this method offers a straightforward and effective solution. DigiCamControl handles the camera-side processing, and Express.js simplifies the image streaming. The results are satisfying!

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