use all cpu cores

.claude/settings.local.json

@@ -46,7 +46,11 @@
       "Bash(pkill -f \"cam-debug\")",
       "Bash(ffmpeg -loglevel error -i /home/dzecevic/repos/CamMonitor/footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 /tmp/stream_h264.mp4)",
       "Bash(ffmpeg -loglevel error -i footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 /tmp/stream_h264.mp4)",
-      "Bash(echo \"exit:$?\")"
+      "Bash(echo \"exit:$?\")",
+      "Bash(time ffmpeg -threads 1 -loglevel error -i footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 /dev/null)",
+      "Bash(time ffmpeg -threads 0 -loglevel error -i footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 /dev/null)",
+      "Bash(time ffmpeg -threads 1 -loglevel error -i footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 -y /tmp/bench1.mp4)",
+      "Bash(time ffmpeg -threads 0 -loglevel error -i footage/20260520/record/A260520_153838_153852.265 -c:v libx264 -preset ultrafast -crf 28 -pix_fmt yuv420p -an -movflags frag_keyframe+empty_moov -f mp4 -y /tmp/bench_all.mp4)"
     ]
   }
 }

docker-compose-prod.yaml

@@ -61,16 +61,20 @@ services:
     security_opt:
       - no-new-privileges:true
 
-    # Limit CPU and memory so a spike in thumbnail requests does not starve the
-    # host (tune to your Atom's actual capacity).
+    # CPU/memory limits — tuned for a 4-core Intel Atom running ffmpeg transcode.
+    # cpus limit: allow all 4 cores so the H.265→H.264 transcode can use
+    #   multi-threaded decoding and encoding simultaneously.
+    #   Lower this (e.g. "2.0") if other services share the host and you want
+    #   to guarantee headroom for them.
+    # memory: 512M covers the Go process + one active ffmpeg transcode at 1080p.
     deploy:
       resources:
         limits:
-          cpus:   "1.0"
-          memory: 256M
+          cpus:   "4.0"
+          memory: 512M
         reservations:
-          cpus:   "0.25"
-          memory: 64M
+          cpus:   "1.0"
+          memory: 128M
 
     # Aggressive health-check so the orchestrator restarts a hung container fast.
     healthcheck:

internal/video/stream.go

@@ -19,6 +19,10 @@ func Stream(w http.ResponseWriter, r *http.Request, absPath, ffmpegPath string)
 
 	cmd := exec.Command(
 		ffmpegPath,
+		// Use all CPU cores for decoding the H.265 input.
+		// This is a global ffmpeg option and must come before -i.
+		// "0" means auto-detect (= number of cores available to the process).
+		"-threads", "0",
 		"-loglevel", "error",
 		"-i", absPath,
 		// Transcode H.265 → H.264 for universal browser support.
@@ -33,6 +37,8 @@ func Stream(w http.ResponseWriter, r *http.Request, absPath, ffmpegPath string)
 		// without this the picture looks washed out.
 		// -an drops the audio track; security camera clips rarely carry useful
 		// audio and stripping it halves the work for the encoder.
+		// libx264 picks its own thread count automatically (matching -threads 0
+		// above), so no separate -x264-params threads= is needed.
 		"-c:v", "libx264",
 		"-preset", "ultrafast",
 		"-crf", "28",