try 2

cht/stream/ffmpeg.py

@@ -64,21 +64,25 @@ def receive_record_and_relay(stream_url, output_path, relay_url):
 
 
 def receive_record_relay_and_detect(stream_url, output_path, relay_url,
-                                    frames_dir, scene_threshold=0.10,
-                                    start_number=1):
+                                    scene_threshold=0.10):
     """Single process: receive TCP → record fMP4 + relay UDP + scene detect.
 
     One ffmpeg process, three output branches from the same TCP input:
-    1. File output — c=copy to fMP4
-    2. UDP relay — c=copy to mpegts for live display
-    3. Scene frames — CUDA decode → select(scene) → showinfo → JPEG files
+    1. File output — c=copy to fMP4 (raw packets, no decode)
+    2. UDP relay — c=copy to mpegts for live display (raw packets)
+    3. Scene frames — Vulkan decode + scdet_vulkan (GPU scene comparison,
+       sc_pass=1 drops non-scene frames on GPU) → hwdownload (only scene
+       frames hit CPU) → showinfo → MJPEG piped to stdout
 
-    The scene filter runs on decoded frames in-process, so detection latency
-    is near-zero (no polling, no file re-reading, no separate process).
-    Stderr must be read continuously to parse showinfo lines.
+    Scene frames are piped to stdout as image2pipe/mjpeg to avoid the image2
+    muxer's one-frame buffering delay. The caller reads JPEG data from stdout
+    and writes files itself. Stderr carries showinfo lines with timestamps.
+    Both stdout and stderr must be read continuously.
     """
-    stream = ffmpeg.input(stream_url, fflags="nobuffer", flags="low_delay",
-                          hwaccel="cuda")
+    stream = ffmpeg.input(
+        stream_url, fflags="nobuffer", flags="low_delay",
+        hwaccel="vulkan", hwaccel_output_format="vulkan",
+    )
 
     # Copy outputs (raw packet remux, no decode)
     file_out = ffmpeg.output(
@@ -93,13 +97,19 @@ def receive_record_relay_and_detect(stream_url, output_path, relay_url,
         c="copy", f="mpegts",
     )
 
-    # Scene detection output (decode + filter → JPEG)
-    select_expr = f"gt(scene,{scene_threshold})"
-    scene_stream = stream.filter("select", select_expr).filter("showinfo")
+    # Scene detection on Vulkan GPU — only scene-change frames leave the GPU
+    scdet_threshold = scene_threshold * 100  # config 0-1 → scdet 0-100
+    scene_stream = (
+        stream
+        .filter("scdet_vulkan", threshold=scdet_threshold, sc_pass=1)
+        .filter("hwdownload")
+        .filter("format", "yuv420p")
+        .filter("showinfo")
+    )
     scene_out = ffmpeg.output(
-        scene_stream, str(frames_dir / "F%04d.jpg"),
-        vsync="vfr", flush_packets=1, **{"q:v": "2"},
-        start_number=start_number,
+        scene_stream, "pipe:1",
+        f="image2pipe", vcodec="mjpeg",
+        vsync="vfr", **{"q:v": "2"},
     )
 
     return ffmpeg.merge_outputs(file_out, relay_out, scene_out).global_args(*GLOBAL_ARGS)