Can You Turn a Bama Bound AI Clip Into a GIF Without the Red Banner Going Orange? Palettes vs Animated WebP, Measured

#!/usr/bin/env python3 """Turn a vertical banner clip into a GIF or animated WebP, then measure what it cost. python3 clip_to_gif.py in.mp4 out.gif [--start 2 --duration 3 --fps 10 --width 320] [--method palette|naive] [--dither sierra2_4a|bayer|none] [--max-kb 4000] python3 clip_to_gif.py in.mp4 out.webp [--quality 70] add --denoise to smooth AI-video grain first (much smaller GIFs) After encoding it decodes the result and the source at the same times and size and reports file size, frame count, frame delays, and colour error (CIE76 delta E) on the red banner and on the whole frame. Exit 1 if --max-kb is set and not met. Needs ffmpeg/ffprobe on PATH, NumPy and Pillow (Pillow decodes the GIF/WebP, because ffmpeg's WebP decoder cannot read animated WebP). """ import argparse, json, os, subprocess, sys import numpy as np from PIL import Image, ImageSequence def run(cmd): subprocess.run(cmd, check=True, stdout=subprocess.DEVNULL, stderr=subprocess.PIPE) def probe_size(path): out = subprocess.run(["ffprobe", "-v", "error", "-select_streams", "v:0", "-show_entries", "stream=width,height", "-of", "json", path], check=True, capture_output=True, text=True).stdout s = json.loads(out)["streams"][0] return s["width"], s["height"] def frames(path, vf, w, h, n=None): """Decode to RGB24 frames through an optional filter chain.""" cmd = ["ffmpeg", "-v", "error", "-i", path] if vf: cmd += ["-vf", vf] cmd += ["-f", "rawvideo", "-pix_fmt", "rgb24", "-"] raw = subprocess.run(cmd, check=True, capture_output=True).stdout a = np.frombuffer(raw, np.uint8).reshape(-1, h, w, 3) return a if n is None else a[:n] def to_lab(rgb): c = rgb.astype(np.float64) / 255.0 c = np.where(c <= 0.04045, c / 12.92, ((c + 0.055) / 1.055) ** 2.4) m = np.array([[0.4124, 0.3576, 0.1805], [0.2126, 0.7152, 0.0722], [0.0193, 0.1192, 0.9505]]) xyz = c @ m.T / np.array([0.95047, 1.0, 1.08883]) f = np.where(xyz > 216 / 24389, np.cbrt(xyz), (24389 / 27 * xyz + 16) / 116) return np.stack([116 * f[..., 1] - 16, 500 * (f[..., 0] - f[..., 1]), 200 * (f[..., 1] - f[..., 2])], -1) def red_mask(rgb): """Saturated, bright, red-ish pixels: the banner, not the field or the sky.""" c = rgb.astype(np.int16); r, g, b = c[..., 0], c[..., 1], c[..., 2] return (r > 120) & (r - g > 70) & (r - b > 50) def encode(a, w_out, chain): if a.out.endswith(".webp"): run(["ffmpeg", "-v", "error", "-y", "-ss", str(a.start), "-t", str(a.duration), "-i", a.src, "-vf", chain, "-an", "-c:v", "libwebp_anim", "-lossless", "0", "-q:v", str(a.quality), "-loop", "0", a.out]) elif a.method == "naive": run(["ffmpeg", "-v", "error", "-y", "-ss", str(a.start), "-t", str(a.duration), "-i", a.src, "-vf", chain, "-an", "-loop", "0", a.out]) else: d = {"bayer": "bayer:bayer_scale=3", "none": "none"}.get(a.dither, a.dither) fc = (f"[0:v]{chain},split[x][y];[x]palettegen=max_colors=256:stats_mode=diff[p];" f"[y][p]paletteuse=dither={d}:diff_mode=rectangle") run(["ffmpeg", "-v", "error", "-y", "-ss", str(a.start), "-t", str(a.duration), "-i", a.src, "-filter_complex", fc, "-an", "-loop", "0", a.out]) def decode_anim(path): """Frames (RGB, after GIF disposal/WebP blending) and per-frame delays in ms.""" im = Image.open(path); fr, delays = [], [] for f in ImageSequence.Iterator(im): fr.append(np.asarray(f.convert("RGB"))); delays.append(f.info.get("duration", 0)) return np.stack(fr), delays def measure(a, w_out, h_out, chain): out_f, delays = decode_anim(a.out) src_f = frames(a.src, f"trim=start={a.start}:duration={a.duration},setpts=PTS-STARTPTS,{chain}", w_out, h_out, len(out_f)) n = min(len(out_f), len(src_f)) out_f, src_f = out_f[:n], src_f[:n] de = np.linalg.norm(to_lab(out_f) - to_lab(src_f), axis=-1) m = red_mask(src_f) return {"file": a.out, "kb": round(os.path.getsize(a.out) / 1024, 1), "width": w_out, "height": h_out, "fps": a.fps, "frames": len(delays), "delays_ms": sorted(set(delays)), "duration_s": round(sum(delays) / 1000, 3), "banner_share": round(float(m.mean()), 3), "banner_dE_mean": round(float(de[m].mean()), 2) if m.any() else None, "frame_dE_mean": round(float(de.mean()), 2)} def main(): p = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter) p.add_argument("src"); p.add_argument("out") p.add_argument("--start", type=float, default=0.0); p.add_argument("--duration", type=float, default=3.0) p.add_argument("--fps", type=int, default=10); p.add_argument("--width", type=int, default=320) p.add_argument("--method", choices=["palette", "naive"], default="palette") p.add_argument("--dither", default="sierra2_4a"); p.add_argument("--quality", type=int, default=70) p.add_argument("--max-kb", type=float, default=0) p.add_argument("--denoise", action="store_true") a = p.parse_args() if a.out.endswith(".gif") and 100 % a.fps: print(f"warning: GIF delays are whole 1/100 s; {a.fps} fps cannot be timed exactly " f"(use 10, 20, 25 or 50)", file=sys.stderr) while True: w0, h0 = probe_size(a.src) w_out = a.width - a.width % 2 h_out = round(h0 * w_out / w0 / 2) * 2 chain = f"fps={a.fps},scale={w_out}:{h_out}:flags=lanczos" if a.denoise: chain = "hqdn3d=8:6:12:12," + chain encode(a, w_out, chain) kb = os.path.getsize(a.out) / 1024 if not a.max_kb or kb <= a.max_kb or a.width * 0.85 < 160: break print(f"{kb:.0f} KB at {w_out} px wide is over {a.max_kb:.0f} KB; shrinking", file=sys.stderr) a.width = int(a.width * 0.85) # too big: shrink 15% and try again r = measure(a, w_out, h_out, chain) r["ok"] = not a.max_kb or r["kb"] <= a.max_kb print(json.dumps(r)) return 0 if r["ok"] else 1 if __name__ == "__main__": sys.exit(main()) 

#!/usr/bin/env bash # Synthetic stand-in for a vertical banner clip (no people, no real footage): # gradient sky, noisy green field, a red banner with white text that sways # left and right, and a soundtrack of short 880 Hz beeps at irregular times # over a quiet 220 Hz hum. # ./make_field_test_clip.sh out.mp4 [WxH] [fps] [seconds] # env NOISE=0..40 sets the field grain (default 18) set -euo pipefail out=${1:-field_test.mp4}; size=${2:-480x854}; fps=${3:-30}; dur=${4:-8} W=${size%x*}; H=${size#*x} FONT=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf BW=$((W*3/4)); BH=$((H/6)); BY=$((H*2/5)) BX="(${W}-${BW})/2+${W}/10*sin(2*PI*t/3.1)*cos(2*PI*t/7.3)" SKY=$((H*2/5)) ffmpeg -v error -y \ -f lavfi -i "gradients=s=${W}x${SKY}:c0=0x2F7FD0:c1=0xBFE3FF:x0=0:y0=0:x1=0:y1=${SKY}:r=${fps}:d=${dur}:speed=0" \ -f lavfi -i "color=c=0x3A8A3A:s=${W}x${H}:r=${fps}:d=${dur}" \ -f lavfi -i "color=c=0xC8102E:s=${BW}x${BH}:r=${fps}:d=${dur}" \ -f lavfi -i "aevalsrc='0.08*sin(2*PI*220*t)+0.6*sin(2*PI*880*t)*(between(t,0.7,0.82)+between(t,2.1,2.22)+between(t,2.6,2.72)+between(t,4.9,5.02)+between(t,6.3,6.42))':s=48000:d=${dur}" \ -filter_complex "[1:v]noise=alls=${NOISE:-18}:allf=t,format=yuv420p[field];\ [field][0:v]overlay=0:0[bg];\ [2:v]drawtext=fontfile=${FONT}:text='TEST BANNER':fontcolor=white:fontsize=$((BH/4)):x=(w-text_w)/2:y=(h-text_h)/2[ban];\ [bg][ban]overlay=x='${BX}':y=${BY},format=yuv420p[v]" \ -map "[v]" -map 3:a -c:v libx264 -preset veryfast -crf 20 -r "$fps" -c:a aac -b:a 128k -t "$dur" "$out" echo "wrote $out (${W}x${H} @ ${fps} fps, ${dur} s)" 

$ NOISE=6 ./make_field_test_clip.sh lo.mp4 $ python3 clip_to_gif.py lo.mp4 n.gif --method naive --start 2 --duration 3 {"kb": 463.1, "frames": 30, "delays_ms": [100], "banner_dE_mean": 26.89, "frame_dE_mean": 21.59, ...} $ python3 clip_to_gif.py lo.mp4 p.gif --start 2 --duration 3 {"kb": 2394.5, "banner_dE_mean": 1.12, "frame_dE_mean": 1.28, ...} $ python3 clip_to_gif.py lo.mp4 pd.gif --denoise --start 2 --duration 3 {"kb": 1219.4, "banner_dE_mean": 1.08, "frame_dE_mean": 1.17, ...} $ python3 clip_to_gif.py lo.mp4 w.webp --start 2 --duration 3 {"kb": 64.0, "banner_dE_mean": 3.59, "frame_dE_mean": 2.07, ...} $ python3 clip_to_gif.py lo.mp4 w12.gif --fps 12 --start 2 --duration 3 warning: GIF delays are whole 1/100 s; 12 fps cannot be timed exactly (use 10, 20, 25 or 50) {"frames": 36, "delays_ms": [80, 90], "duration_s": 3.0, ...} 

$ python3 clip_to_gif.py lo.mp4 cap.gif --width 480 --fps 20 --denoise --max-kb 1500 --start 2 --duration 3 2876 KB at 480 px wide is over 1500 KB; shrinking 3637 KB at 408 px wide is over 1500 KB; shrinking 2463 KB at 346 px wide is over 1500 KB; shrinking 1757 KB at 294 px wide is over 1500 KB; shrinking {"kb": 1313.0, "width": 248, "height": 442, "fps": 20, "banner_dE_mean": 1.27, "ok": true}