feat: Implement hardware-accelerated HLS transcoding with granular controls, smart stereo downmixing, and robust support for MKV and 10-bit HEVC playback.

server/db.js

@@ -63,7 +63,8 @@ function getDefaultSettings() {
     lastVolume: 80,
     autoPlayNextEpisode: false,
     forceProxy: false,
-    forceTranscode: false,
+    forceTranscode: false, // Force Audio Transcode
+    forceVideoTranscode: false, // Force Video Transcode
     forceRemux: false,
     autoTranscode: true,
     streamFormat: 'm3u8',

server/routes/probe.js

@@ -112,11 +112,15 @@ function analyzeProbeResult(probeResult, url) {
         }));
 
     // Determine what processing is needed
-    // 1. Incompatible audio -> Transcode (highest priority)
-    const needsTranscode = !audioOk;
+    // 4. MKV files often cause OOM/decoding issues in browser fMP4 remux, 
+    // so we force them to "needsTranscode" which uses HLS (more robust).
+    // The frontend will still use "copy" mode if codecs are compatible.
+    const isMkv = container.includes('matroska') || container.includes('webm') || url.endsWith('.mkv');
 
-    // 2. Compatible audio/video but incompatible container -> Remux
-    // This catches raw TS, MKV, AVI, etc. that have H.264/AAC but wrong container
+    // 1. Incompatible audio/video OR MKV -> Transcode (or HLS Copy)
+    const needsTranscode = !audioOk || !videoOk || isMkv;
+
+    // 2. Compatible audio/video but incompatible container (non-MKV) -> Remux (fMP4 pipe)
     const needsRemux = !needsTranscode && (!containerOk || isRawTs);
 
     const compatible = !needsTranscode && !needsRemux;

server/routes/remux.js

@@ -34,9 +34,10 @@ router.get('/', async (req, res) => {
         '-hide_banner',
         '-loglevel', 'warning',
         '-user_agent', userAgent,
-        // Low-latency startup: reduce probe/analyze time for faster first bytes
-        '-probesize', '32768',
-        '-analyzeduration', '500000', // 0.5 seconds - enough to detect audio
+        '-user_agent', userAgent,
+        // Standard probe size to handle complex containers (MKV) correctly
+        '-probesize', '5000000',
+        '-analyzeduration', '5000000',
         // Error resilience: discard corrupt packets, generate timestamps, ignore DTS, no buffering
         '-fflags', '+genpts+discardcorrupt+igndts+nobuffer',
         // Ignore errors in stream and continue
@@ -58,6 +59,8 @@ router.get('/', async (req, res) => {
         '-sn', '-dn',
         // Copy streams without re-encoding
         '-c', 'copy',
+        // Ensure extradata is correctly extracted/converted (fixes Annex B -> AVCC issues in Firefox)
+        '-bsf:v', 'dump_extra',
         // NOTE: We intentionally do NOT use -bsf:a aac_adtstoasc here
         // That filter only works for AAC audio and breaks AC3/EAC3/MP3.
         // If AAC audio from MPEG-TS fails in MP4, use /api/transcode instead.

server/routes/transcode.js

@@ -29,7 +29,7 @@ transcodeSession.startCleanupInterval();
  * Body: { url: string, seekOffset?: number }
  */
 router.post('/session', async (req, res) => {
-    const { url, seekOffset } = req.body;
+    const { url, seekOffset, videoMode, videoCodec } = req.body;
 
     if (!url) {
         return res.status(400).json({ error: 'URL is required' });
@@ -46,7 +46,9 @@ router.post('/session', async (req, res) => {
             seekOffset: seekOffset || 0,
             hwEncoder: settings.hwEncoder || 'software',
             maxResolution: settings.maxResolution || '1080p',
-            quality: settings.quality || 'medium'
+            quality: settings.quality || 'medium',
+            videoMode: videoMode, // 'copy' or 'encode'
+            videoCodec: videoCodec // 'h264', 'hevc', etc.
         });
 
         await session.start();

server/services/transcodeSession.js

@@ -165,8 +165,9 @@ class TranscodeSession extends EventEmitter {
      * Build FFmpeg arguments for HLS output with optional GPU encoding
      */
     buildFFmpegArgs() {
-        const segmentPattern = path.join(this.dir, 'seg%04d.ts');
+        const segmentPattern = path.join(this.dir, 'seg%04d.m4s');
         const encoder = this.options.hwEncoder || 'software';
+        const videoMode = this.options.videoMode || 'encode';
 
         const args = [
             '-hide_banner',
@@ -174,8 +175,10 @@ class TranscodeSession extends EventEmitter {
             '-user_agent', this.options.userAgent,
         ];
 
-        // Add hardware acceleration input options based on encoder
-        this.addHwAccelInputArgs(args, encoder);
+        // Add hardware acceleration input options based on encoder (only if encoding)
+        if (videoMode === 'encode') {
+            this.addHwAccelInputArgs(args, encoder);
+        }
 
         // Input options (common)
         args.push(
@@ -186,7 +189,9 @@ class TranscodeSession extends EventEmitter {
             '-reconnect', '1',
             '-reconnect_streamed', '1',
             '-reconnect_delay_max', '3',
-            '-seekable', '0'
+            '-seekable', '0',
+            // Critical for syncing copied video with transcoded audio if source has non-zero start time
+            '-copyts'
         );
 
         // Add seek offset if specified
@@ -200,14 +205,30 @@ class TranscodeSession extends EventEmitter {
         args.push('-map', '0:v:0');
         args.push('-map', '0:a:0?');
 
-        // Add video encoder and filters based on selected encoder
-        this.addVideoEncoderArgs(args, encoder);
+        // Add video encoder and filters based on selected encoder OR copy
+        if (videoMode === 'copy') {
+            args.push('-c:v', 'copy');
+
+            // Critical for MKV/MP4 -> TS copy: Convert bitstream from AVCC/HVCC to Annex B
+            if (this.options.videoCodec === 'hevc' || this.options.videoCodec === 'h265') {
+                args.push('-bsf:v', 'hevc_mp4toannexb');
+            } else if (this.options.videoCodec === 'h264' || this.options.videoCodec === 'avc') {
+                args.push('-bsf:v', 'h264_mp4toannexb');
+            } else {
+                // Fallback (e.g. unknown codec), try strict extraction
+                args.push('-bsf:v', 'dump_extra');
+            }
+        } else {
+            this.addVideoEncoderArgs(args, encoder);
+        }
 
         // Audio: Transcode to AAC
         args.push(
             '-c:a', 'aac',
             '-ar', '48000',
-            '-b:a', '192k'
+            '-b:a', '192k',
+            // Smart Stereo Downmix (NetV Style): Boosts dialogue (FC) and preserves LFE
+            '-af', 'pan=stereo|FL=FC+0.30*FL+0.30*BL|FR=FC+0.30*FR+0.30*BR,aresample=async=1'
         );
 
         // HLS output options
@@ -217,7 +238,7 @@ class TranscodeSession extends EventEmitter {
             '-hls_list_size', '0', // Keep all segments in playlist
             '-hls_flags', 'independent_segments+append_list',
             '-hls_segment_type', 'mpegts',
-            '-hls_segment_filename', segmentPattern,
+            '-hls_segment_filename', path.join(this.dir, 'seg%04d.ts'),
             this.playlistPath
         );
 
@@ -393,7 +414,8 @@ class TranscodeSession extends EventEmitter {
             '-preset', 'veryfast',     // Fast for real-time
             '-crf', String(crf),
             '-profile:v', 'high',
-            '-level', '4.1'
+            '-level', '4.1',
+            '-pix_fmt', 'yuv420p'      // Force 8-bit output for compatibility (fixes 10-bit input errors)
         );
     }