phase 3

detect/stages/frame_extractor.py

@@ -0,0 +1,102 @@
+"""
+Stage 1 — Frame Extraction
+
+Extracts frames from a video at a configurable FPS using FFmpeg.
+Emits log + stats_update SSE events as it works.
+"""
+
+from __future__ import annotations
+
+import subprocess
+import tempfile
+from pathlib import Path
+
+import numpy as np
+from PIL import Image
+
+from core.ffmpeg.probe import probe_file
+from detect.events import push_detect_event
+from detect.models import Frame
+from detect.profiles.base import FrameExtractionConfig
+
+
+def extract_frames(
+    video_path: str,
+    config: FrameExtractionConfig,
+    job_id: str | None = None,
+) -> list[Frame]:
+    """
+    Extract frames from video at the configured FPS.
+
+    Uses FFmpeg to decode frames as raw images, then loads them
+    as numpy arrays. Caps at config.max_frames.
+    """
+    probe = probe_file(video_path)
+    duration = probe.duration or 0.0
+
+    if job_id:
+        push_detect_event(job_id, "log", {
+            "level": "INFO",
+            "stage": "FrameExtractor",
+            "msg": f"Starting extraction: {Path(video_path).name} "
+                   f"({duration:.1f}s, {probe.width}x{probe.height}, fps={config.fps})",
+        })
+
+    frames: list[Frame] = []
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        pattern = str(Path(tmpdir) / "frame_%06d.jpg")
+
+        cmd = [
+            "ffmpeg", "-i", video_path,
+            "-vf", f"fps={config.fps}",
+            "-q:v", "2",
+            "-frames:v", str(config.max_frames),
+            pattern,
+            "-y", "-loglevel", "warning",
+        ]
+
+        result = subprocess.run(cmd, capture_output=True, text=True)
+
+        if result.returncode != 0:
+            if job_id:
+                push_detect_event(job_id, "log", {
+                    "level": "ERROR",
+                    "stage": "FrameExtractor",
+                    "msg": f"FFmpeg failed: {result.stderr[:200]}",
+                })
+            raise RuntimeError(f"FFmpeg failed: {result.stderr}")
+
+        frame_files = sorted(Path(tmpdir).glob("frame_*.jpg"))
+
+        for i, fpath in enumerate(frame_files):
+            img = Image.open(fpath)
+            arr = np.array(img)
+            timestamp = i / config.fps
+
+            frames.append(Frame(
+                sequence=i,
+                chunk_id=0,
+                timestamp=timestamp,
+                image=arr,
+            ))
+
+        if job_id:
+            push_detect_event(job_id, "log", {
+                "level": "INFO",
+                "stage": "FrameExtractor",
+                "msg": f"Extracted {len(frames)} frames",
+            })
+            push_detect_event(job_id, "stats_update", {
+                "frames_extracted": len(frames),
+                "frames_after_scene_filter": 0,
+                "regions_detected": 0,
+                "regions_resolved_by_ocr": 0,
+                "regions_escalated_to_local_vlm": 0,
+                "regions_escalated_to_cloud_llm": 0,
+                "cloud_llm_calls": 0,
+                "processing_time_seconds": 0.0,
+                "estimated_cloud_cost_usd": 0.0,
+            })
+
+    return frames