#!/usr/bin/env python3
"""Check an encoded video for what stills miss: cuts, one-frame blinks, and text that shimmers while it should hold still.

  python3 qa-video.py film.mp4                         hard cuts (with times) and blink candidates
  python3 qa-video.py film.mp4 --hold 1680 1790 360 420 900 300
        largest frame-to-frame change inside region x,y,w,h over frames a..b (60 fps frame numbers).
        Held text should change by ~2-4 levels (encoder noise); 20+ means it moves or shimmers.
  python3 qa-video.py film.mp4 --where 735 748         bounding box of what changed in each frame of a range

Compare the hard-cut list with the cuts you planned; anything else hard is a bug (a scene popping
instead of animating out). Blink candidates are frames where something changes and reverts: look at
them, though fast deliberate flips (cycling words, caption streams) show up too.
"""
import argparse, glob, re, subprocess, tempfile
from common import ffmpeg

ap = argparse.ArgumentParser()
ap.add_argument("video"); ap.add_argument("--hold", nargs=6, type=int); ap.add_argument("--where", nargs=2, type=int)
ap.add_argument("--fps", type=float, default=60)
a = ap.parse_args(); FF = ffmpeg()


def frames(a0, b0, extra=""):
    from PIL import Image
    d = tempfile.mkdtemp()
    subprocess.run([FF, "-v", "error", "-i", a.video, "-vf", f"select='between(n,{a0},{b0})'{extra},format=gray", "-vsync", "0", f"{d}/f%05d.png"], check=True)
    return [Image.open(f) for f in sorted(glob.glob(f"{d}/f*.png"))]


if a.hold:
    from PIL import ImageChops
    f0, f1, x, y, w, h = a.hold
    ims = frames(f0, f1, f",crop={w}:{h}:{x}:{y}"); worst = (0, None)
    for k in range(1, len(ims)):
        m = ImageChops.difference(ims[k], ims[k - 1]).getextrema()[1]
        if m > worst[0]: worst = (m, f0 + k)
    print(f"frames {f0}-{f1}, region {x},{y} {w}x{h}: largest change {worst[0]} at frame {worst[1]} ({(worst[1] or 0) / a.fps:.3f}s)")
elif a.where:
    from PIL import ImageChops
    ims = frames(*a.where)
    for k in range(1, len(ims)):
        bb = ImageChops.difference(ims[k], ims[k - 1]).point(lambda v: 255 if v > 24 else 0).getbbox()
        print(a.where[0] + k, f"{(a.where[0] + k) / a.fps:.3f}s", bb)
else:
    log = tempfile.mktemp(suffix=".txt")
    subprocess.run([FF, "-v", "error", "-i", a.video, "-vf", f"scale=480:270,signalstats,metadata=print:key=lavfi.signalstats.YDIF:file={log}", "-f", "null", "-"], check=True)
    v = [float(x) for x in re.findall(r"YDIF=([\d.]+)", open(log).read())]
    print(f"{len(v)} frames; hard cuts at", [round(i / a.fps, 2) for i, d in enumerate(v) if d > 60])
    print("blink candidates:", [round(i / a.fps, 3) for i in range(1, len(v) - 2)
                                if v[i] > 4 and v[i + 1] > 4 and v[i] > 3 * max(v[i - 1], 0.3) and v[i + 1] > 3 * max(v[i + 2], 0.3)])