Does the Red Banner Flicker or Change Colour in My Bama Bound AI Clip? Tracking Banner Hue Frame by Frame in Python

#!/usr/bin/env python3 """Track the red banner's colour frame by frame in a vertical clip. For every decoded frame (downscaled to 160 px wide) we build a "banner red" mask in HSV, then record the mask's area share and its circular-mean hue. We flag: * flicker: hue jumps more than --jump degrees between consecutive frames * missing: banner area drops below --min-area of the clip's median area * drift: median hue of the last second differs from the first second by > --drift deg Usage: banner_hue.py clip.mp4 [--csv out.csv] exit 0 = clean, 1 = flagged, 2 = error Needs ffmpeg/ffprobe on PATH and numpy. """ import argparse, csv, json, subprocess, sys import numpy as np W = 160 def probe(path): out = subprocess.run(["ffprobe", "-v", "error", "-select_streams", "v:0", "-show_entries", "stream=width,height,avg_frame_rate", "-of", "json", path], capture_output=True, text=True, check=True).stdout s = json.loads(out)["streams"][0] num, den = s["avg_frame_rate"].split("/") return s["width"], s["height"], float(num) / float(den) def frames(path, w, h): hh = int(round(h * W / w / 2)) * 2 p = subprocess.Popen(["ffmpeg", "-v", "error", "-i", path, "-vf", f"scale={W}:{hh}", "-f", "rawvideo", "-pix_fmt", "rgb24", "-"], stdout=subprocess.PIPE) size = W * hh * 3 while True: buf = p.stdout.read(size) if len(buf) < size: break yield np.frombuffer(buf, np.uint8).reshape(hh, W, 3) p.wait() def hsv(rgb): x = rgb.astype(np.float32) / 255.0 r, g, b = x[..., 0], x[..., 1], x[..., 2] mx, mn = x.max(-1), x.min(-1) d = mx - mn + 1e-6 h = np.where(mx == r, ((g - b) / d) % 6, np.where(mx == g, (b - r) / d + 2, (r - g) / d + 4)) * 60 s = np.where(mx > 0, (mx - mn) / (mx + 1e-6), 0) return h, s, mx def banner_stats(rgb): h, s, v = hsv(rgb) # "red-ish": hue within 40 deg of 0 (covers crimson..orange so a shift stays inside the mask)  dist = np.minimum(h, 360 - h) mask = (dist < 40) & (s > 0.5) & (v > 0.35) area = float(mask.mean()) if mask.sum() < 20: return area, None a = np.deg2rad(h[mask]) hue = float(np.rad2deg(np.arctan2(np.sin(a).mean(), np.cos(a).mean()))) % 360 return area, hue def circ_median(hs): # hues sit around 0/360, so take the median of offsets from the first value  ref = hs[0] off = [((x - ref + 180) % 360) - 180 for x in hs] return (ref + float(np.median(off))) % 360 def hue_diff(a, b): d = abs(a - b) % 360 return min(d, 360 - d) def main(): ap = argparse.ArgumentParser() ap.add_argument("clip"); ap.add_argument("--csv") ap.add_argument("--jump", type=float, default=8.0) ap.add_argument("--drift", type=float, default=6.0) ap.add_argument("--min-area", type=float, default=0.5) a = ap.parse_args() try: w, h, fps = probe(a.clip) except Exception as e: print(f"cannot read {a.clip}: {e}", file=sys.stderr); return 2 rows = [(i / fps, *banner_stats(f)) for i, f in enumerate(frames(a.clip, w, h))] if not rows: print("no frames decoded", file=sys.stderr); return 2 if a.csv: with open(a.csv, "w", newline="") as f: cw = csv.writer(f); cw.writerow(["t", "area", "hue"]) cw.writerows([(f"{t:.3f}", f"{ar:.4f}", "" if hu is None else f"{hu:.1f}") for t, ar, hu in rows]) med_area = float(np.median([r[1] for r in rows])) flags = [] for (t0, _, h0), (t1, ar1, h1) in zip(rows, rows[1:]): if h0 is not None and h1 is not None and hue_diff(h0, h1) > a.jump: flags.append({"t": round(t1, 3), "kind": "flicker", "detail": f"hue {h0:.1f} -> {h1:.1f}"}) if med_area > 0 and ar1 < a.min_area * med_area: flags.append({"t": round(t1, 3), "kind": "missing", "detail": f"area {ar1:.3f} vs median {med_area:.3f}"}) n = max(1, int(round(fps))) first = [r[2] for r in rows[:n] if r[2] is not None] last = [r[2] for r in rows[-n:] if r[2] is not None] drift = hue_diff(circ_median(first), circ_median(last)) if first and last else None if drift is not None and drift > a.drift: flags.append({"t": round(rows[-1][0], 3), "kind": "drift", "detail": f"{drift:.1f} deg first->last second"}) hues = [r[2] for r in rows if r[2] is not None] print(json.dumps({"clip": a.clip, "frames": len(rows), "fps": round(fps, 3), "median_area": round(med_area, 4), "median_hue": None if not hues else round(circ_median(hues), 1), "drift_deg": None if drift is None else round(drift, 1), "flags": flags}, indent=2)) return 1 if flags else 0 if __name__ == "__main__": sys.exit(main()) 

#!/usr/bin/env bash # Synthetic stand-in for a vertical banner clip: sky, green field, a red banner with # white text, a 440 Hz tone. No people, no real footage. # ./make_banner_test_clip.sh out.mp4 [steady|flicker|drift] # env BX, BY move the banner (default 60, 330) # flicker = banner turns orange at 4.0-4.2 s; drift = whole frame hue rotates 2 deg/s set -euo pipefail out=${1:-banner_test.mp4}; mode=${2:-steady} FONT=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf banner="drawbox=x=${BX:-60}:y=${BY:-330}:w=360:h=150:color=0xC8102E:t=fill" [ "$mode" = flicker ] && banner="$banner,drawbox=x=${BX:-60}:y=${BY:-330}:w=360:h=150:color=0xF07820:t=fill:enable='between(t,4,4.2)'" post=""; [ "$mode" = drift ] && post=",hue=h=2*t" ffmpeg -v error -y -f lavfi -i "color=c=0x3A8A3A:s=480x854:r=30:d=8" \ -f lavfi -i "sine=frequency=440:duration=8:sample_rate=48000" \ -filter_complex "[0:v]drawbox=x=0:y=0:w=iw:h=300:color=0x87CEEB:t=fill,${banner},drawtext=fontfile=${FONT}:text='TEST BANNER':fontcolor=white:fontsize=40:x=${BX:-60}+(360-text_w)/2:y=${BY:-330}+55${post},format=yuv420p[v]" \ -map "[v]" -map 1:a -c:v libx264 -preset veryfast -crf 20 -c:a aac -b:a 128k -shortest "$out" echo "wrote $out ($mode)" 

$ ./make_banner_test_clip.sh steady.mp4 $ ./make_banner_test_clip.sh flicker.mp4 flicker $ ./make_banner_test_clip.sh drift.mp4 drift $ python3 banner_hue.py steady.mp4 -> median_hue 350.4, drift 0.0, flags [] exit 0 $ python3 banner_hue.py flicker.mp4 -> flags: flicker at 4.0 s (hue -> 25.5), flicker at 4.233 s exit 1 $ python3 banner_hue.py drift.mp4 -> drift 16.2 deg first->last second exit 1