How to add a time warp scan with Claude

Add a time warp scan to input.mp4: a horizontal cyan (60, 230, 255) line runs across the full width, starting at the top edge at 1 second and moving down at a steady speed to reach the bottom edge at 4.5 seconds. Every row of pixels the line has passed freezes on the frame from the moment the line crossed it; rows below the line keep playing. Draw the line with a 4-pixel solid core and a soft glow fading out over about 14 pixels above and below it. Once the line reaches the bottom it disappears and the finished frozen picture holds to the end. Nothing changes before 1 second. Use Python with numpy to build the frames and ffmpeg to encode them (no ffmpeg drawtext), keep the size, 30fps, 6-second length and audio, and save it as output.mp4.

#!/usr/bin/env python3
"""Time warp scan: a glowing cyan line sweeps down the frame, and every row it passes freezes on that moment, so a moving shot ends up stretched out of shape.

Usage: python3 time-warp-scan.py input.mp4 output.mp4
Needs ffmpeg and numpy (pip install numpy).
"""
import json
import subprocess
import sys

import numpy as np

START = 1.0                # second the line leaves the top edge
SCAN = 3.5                 # seconds it takes to reach the bottom (the frame stays frozen after)
FPS = 30                   # output frame rate
COLOR = (60, 230, 255)     # line color
THICK = 4                  # solid core of the line, in pixels
GLOW = 14                  # how far the soft glow spreads either side of the line, in pixels


def probe(path):
    info = json.loads(subprocess.check_output(["ffprobe", "-v", "error", "-select_streams", "v:0", "-show_entries",
                                               "stream=width,height", "-of", "json", path]))
    return info["streams"][0]["width"], info["streams"][0]["height"]


def frames(path):
    """Decode a clip as RGB frames at FPS."""
    ff = subprocess.Popen(["ffmpeg", "-v", "error", "-i", path, "-vf", f"fps={FPS}",
                           "-f", "rawvideo", "-pix_fmt", "rgb24", "-"], stdout=subprocess.PIPE)
    while True:
        data = ff.stdout.read(w * h * 3)
        if len(data) < w * h * 3:
            return
        yield np.frombuffer(data, np.uint8).reshape(h, w, 3)


def draw_line(img, y):
    """Blend a glowing horizontal line into img at row y."""
    dy = np.abs(np.arange(h) - y)[:, None, None]
    alpha = np.where(dy <= THICK / 2, 1.0, 0.7 * np.exp(-((dy - THICK / 2) / (GLOW / 2)) ** 2))
    return (img * (1 - alpha) + np.array(COLOR, np.float32) * alpha).astype(np.uint8)


src, out = sys.argv[1:3]
w, h = probe(src)
frozen = np.zeros((h, w, 3), np.uint8)   # rows above the line keep the frame from when the line crossed them
line = 0                                 # rows above this are frozen

enc = subprocess.Popen(["ffmpeg", "-y", "-v", "error", "-f", "rawvideo", "-pix_fmt", "rgb24", "-s", f"{w}x{h}",
                        "-r", str(FPS), "-i", "-", "-i", src, "-map", "0:v", "-map", "1:a?",
                        "-c:v", "libx264", "-crf", "18", "-pix_fmt", "yuv420p", "-c:a", "copy", "-shortest", out],
                       stdin=subprocess.PIPE)
for i, frame in enumerate(frames(src)):
    t = i / FPS
    frozen[line:] = frame[line:]     # rows the line crosses now freeze on this frame; rows below it stay live
    line = round(min(max((t - START) / SCAN, 0), 1) * h)
    picture = draw_line(frozen, line) if 0 < line < h else frozen
    enc.stdin.write(picture.tobytes())
enc.stdin.close()
if enc.wait():
    sys.exit("ffmpeg failed")