feat: add subtitle extraction and display for MKV/container streams

server/index.js

@@ -89,6 +89,7 @@ app.use('/api/favorites', require('./routes/favorites'));
 app.use('/api/transcode', require('./routes/transcode'));
 app.use('/api/remux', require('./routes/remux'));
 app.use('/api/probe', require('./routes/probe'));
+app.use('/api/subtitle', require('./routes/subtitle'));
 app.use('/api/settings', require('./routes/settings'));
 
 // SPA fallback - serve index.html for all non-API routes

server/routes/probe.js

@@ -32,6 +32,7 @@ function probeStream(url, ffprobePath, timeout = 15000) {
     return new Promise((resolve, reject) => {
         const args = [
             '-v', 'error',
+            '-user_agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36',
             '-print_format', 'json',
             '-show_streams',
             '-show_format',
@@ -100,6 +101,16 @@ function analyzeProbeResult(probeResult, url) {
     // Check if it's a raw TS stream (not HLS)
     const isRawTs = (container.includes('mpegts') || url.endsWith('.ts')) && !url.includes('.m3u8');
 
+    // Extract subtitle tracks
+    const subtitles = streams
+        .filter(s => s.codec_type === 'subtitle' && s.codec_name !== 'timed_id3' && s.codec_name !== 'bin_data')
+        .map(s => ({
+            index: s.index,
+            language: s.tags?.language || 'und',
+            title: s.tags?.title || s.tags?.language || `Track ${s.index}`,
+            codec: s.codec_name
+        }));
+
     // Determine what processing is needed
     // 1. Incompatible audio -> Transcode (highest priority)
     const needsTranscode = !audioOk;
@@ -116,7 +127,8 @@ function analyzeProbeResult(probeResult, url) {
         container: container,
         compatible: compatible,
         needsRemux: needsRemux,
-        needsTranscode: needsTranscode
+        needsTranscode: needsTranscode,
+        subtitles: subtitles
     };
 }
 

server/routes/remux.js

@@ -26,6 +26,7 @@ router.get('/', (req, res) => {
     const args = [
         '-hide_banner',
         '-loglevel', 'warning',
+        '-user_agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36',
         // Low-latency startup: reduce probe/analyze time for faster first bytes
         '-probesize', '32768',
         '-analyzeduration', '500000', // 0.5 seconds - enough to detect audio

server/routes/subtitle.js

@@ -0,0 +1,58 @@
+const express = require('express');
+const router = express.Router();
+const { spawn } = require('child_process');
+
+/**
+ * Subtitle extraction endpoint
+ * GET /api/subtitle?url=...&index=...
+ * 
+ * Extracts a specific subtitle track and converts it to WebVTT on the fly.
+ */
+router.get('/', (req, res) => {
+    const { url, index } = req.query;
+
+    if (!url || index === undefined) {
+        return res.status(400).json({ error: 'URL and index parameters are required' });
+    }
+
+    const ffmpegPath = req.app.locals.ffmpegPath || 'ffmpeg';
+    // console.log(`[Subtitle] Extracting track ${index} from: ${url}`);
+
+    const args = [
+        '-hide_banner',
+        '-loglevel', 'warning',
+        '-user_agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36',
+        '-probesize', '5000000',
+        '-analyzeduration', '5000000',
+        '-i', url,
+        '-map', `0:${index}`,
+        '-c:s', 'webvtt',
+        '-f', 'webvtt',
+        '-'
+    ];
+
+    const ffmpeg = spawn(ffmpegPath, args);
+
+    res.setHeader('Content-Type', 'text/vtt');
+    res.setHeader('Access-Control-Allow-Origin', '*');
+
+    // Pipe stdout to response
+    ffmpeg.stdout.pipe(res);
+
+    ffmpeg.stderr.on('data', (data) => {
+        // console.error(`[Subtitle FFmpeg] ${data}`);
+    });
+
+    req.on('close', () => {
+        ffmpeg.kill('SIGKILL');
+    });
+
+    ffmpeg.on('error', (err) => {
+        console.error('[Subtitle] Failed to spawn FFmpeg:', err);
+        if (!res.headersSent) {
+            res.status(500).send('Subtitle extraction failed');
+        }
+    });
+});
+
+module.exports = router;

server/routes/transcode.js

@@ -25,6 +25,7 @@ router.get('/', (req, res) => {
     const args = [
         '-hide_banner',
         '-loglevel', 'warning',
+        '-user_agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36',
         // Faster startup - reduced probe/analyze for quicker first bytes
         '-probesize', '2000000', // 2MB (reduced from 5MB)
         '-analyzeduration', '3000000', // 3 seconds (reduced from 10s)