not use vulkan

cht/stream/ffmpeg.py

@@ -70,9 +70,8 @@ def receive_record_relay_and_detect(stream_url, output_path, relay_url,
     One ffmpeg process, three output branches from the same TCP input:
     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
+    3. Scene frames — CUDA decode (GPU) → select(scene) + showinfo (CPU)
+       → MJPEG piped to stdout
 
     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
@@ -81,7 +80,7 @@ def receive_record_relay_and_detect(stream_url, output_path, relay_url,
     """
     stream = ffmpeg.input(
         stream_url, fflags="nobuffer", flags="low_delay",
-        hwaccel="vulkan", hwaccel_output_format="vulkan",
+        hwaccel="cuda",
     )
 
     # Copy outputs (raw packet remux, no decode)
@@ -97,15 +96,10 @@ def receive_record_relay_and_detect(stream_url, output_path, relay_url,
         c="copy", f="mpegts",
     )
 
-    # 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 detection: CUDA decode (GPU) → select filter (CPU, lightweight)
+    # → showinfo → MJPEG piped to stdout (avoids image2 muxer one-frame buffer)
+    select_expr = f"gt(scene,{scene_threshold})"
+    scene_stream = stream.filter("select", select_expr).filter("showinfo")
     scene_out = ffmpeg.output(
         scene_stream, "pipe:1",
         f="image2pipe", vcodec="mjpeg",