fix(pipeline): probe duration via cv2 (no ffprobe dep); wire MASTER_MAX_W; fps-sync note

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tools/pipeline/run.py

@@ -1,6 +1,6 @@
-"""Thin runner: ffprobe the source, then execute the frame -> loop -> transcode
-stages with tools.pipeline.ffmpeg_ops. The pure arg builders are unit-tested;
-this glue is covered by the opt-in integration test."""
+"""Thin runner: probe the source duration, then execute the frame -> loop ->
+transcode stages with tools.pipeline.ffmpeg_ops. The pure arg builders are
+unit-tested; this glue is covered by the opt-in integration test."""
 
 from __future__ import annotations
 
@@ -22,13 +22,17 @@ def resolve_ffmpeg() -> str:
     return imageio_ffmpeg.get_ffmpeg_exe()
 
 
-def probe_duration(src, *, ff: str = "ffprobe") -> float:
-    out = subprocess.run(
-        [ff, "-v", "quiet", "-show_entries", "format=duration",
-         "-of", "csv=p=0", str(src)],
-        capture_output=True, text=True, check=True,
-    ).stdout.strip()
-    return float(out)
+def probe_duration(src) -> float:
+    """Clip duration in seconds via cv2 (frame_count / fps) — avoids a system
+    ffprobe dependency (imageio-ffmpeg ships ffmpeg only; the Pi has no ffprobe)."""
+    import cv2
+    cap = cv2.VideoCapture(str(src))
+    fps = cap.get(cv2.CAP_PROP_FPS) or 0.0
+    frames = cap.get(cv2.CAP_PROP_FRAME_COUNT) or 0.0
+    cap.release()
+    if fps <= 0:
+        raise ValueError(f"could not read fps from {src}")
+    return frames / fps
 
 
 def _run(args: list[str]) -> None:
@@ -36,10 +40,13 @@ def _run(args: list[str]) -> None:
 
 
 def process_clip(src, out_dir, *, start: float = 0.0, duration: float | None = None,
-                 overlap: float = 1.0, master_w: int = 3840, master_h: int = 2160,
+                 overlap: float = 1.0, master_w: int = MASTER_MAX_W, master_h: int = 2160,
                  ff: str | None = None) -> dict:
     """Run stages 2–4 for one clip; return {'master','proxy','loop','mezzanine'} paths.
-    `duration` defaults to the full source length (minus the trim start)."""
+    `duration` defaults to the full source length (minus the trim start).
+    Note: `crossfade_loop_args` uses a fixed fps only to satisfy xfade's
+    constant-frame-rate requirement; the final output fps is set by `transcode_args`
+    (both default 30 — keep in sync if overridden)."""
     ff = ff or resolve_ffmpeg()
     src = Path(src)
     out_dir = Path(out_dir)