Prevent ffmpeg pipe probe deadlock

src/remove_ai_watermarks/video_encoding.py

@@ -286,8 +286,12 @@ def raw_video_command(
     ffmpeg = shutil.which("ffmpeg")
     if ffmpeg is None:
         raise RuntimeError("Video processing requires ffmpeg on PATH")
+    # The pipe format and stream geometry are already explicit. FFmpeg 6 can
+    # otherwise wait for its normal analysis window while the producer blocks
+    # on a full pipe, before the second (audio) input has been opened.
+    pipe_input = ["-analyzeduration", "0", "-probesize", "32", "-i", "pipe:0"]
     frame_input = (
-        ["-f", "nut", "-i", "pipe:0"]
+        ["-f", "nut", *pipe_input]
         if timestamped_input
         else [
             "-f",
@@ -298,8 +302,7 @@ def raw_video_command(
             f"{width}x{height}",
             "-r",
             f"{fps:.12g}",
-            "-i",
-            "pipe:0",
+            *pipe_input,
         ]
     )
     command = [