Vapoursynth SCDetect

def SCDetect(clip: vs.VideoNode, threshold: float = 0.1, plane: int = 0) -> vs.VideoNode:
    """
    Scene change detection with _SceneChangePrev/_SceneChangeNext frame properties.
    Uses core.misc.SCDetect if available (plane=0 only), otherwise falls back to
    a std.PlaneStats-based reimplementation.

    Args:
        clip      : Input clip
        threshold : Scene change threshold (default: 0.1, must be 0.0–1.0)
        plane     : Plane to analyze; only honoured in fallback path —
                    misc.SCDetect always uses plane 0

    Returns:
        Clip with _SceneChangePrev and _SceneChangeNext frame properties set.
    """
    if not isinstance(clip, vs.VideoNode):
        raise vs.Error('SCDetect: this is not a clip')
    if not (0.0 <= threshold <= 1.0):
        raise vs.Error('SCDetect: threshold must be between 0.0 and 1.0')
    if clip.num_frames < 2:
        raise vs.Error('SCDetect: clip must have more than one frame')

    if hasattr(core, 'misc') and plane == 0:
        if clip.format.color_family == vs.RGB:
            sc = clip.resize.Point(format=vs.GRAY8, matrix_s='709')
            sc = core.misc.SCDetect(sc, threshold=threshold)

            def _copy_props(n: int, f: list[vs.VideoFrame]) -> vs.VideoFrame:
                fout = f[0].copy()
                fout.props['_SceneChangePrev'] = f[1].props['_SceneChangePrev']
                fout.props['_SceneChangeNext'] = f[1].props['_SceneChangeNext']
                return fout

            return clip.std.ModifyFrame(clips=[clip, sc], selector=_copy_props)

        return core.misc.SCDetect(clip, threshold=threshold)

    # prev_stats[n] = diff(frame_{n-1}, frame_n)  → SceneChangePrev
    # next_stats[n] = diff(frame_n,     frame_{n+1}) → SceneChangeNext
    prev_shifted = clip.std.DuplicateFrames(0).std.Trim(last=clip.num_frames - 1)
    prev_stats = core.std.PlaneStats(prev_shifted, clip, plane=plane)
    next_stats = core.std.PlaneStats(clip, clip.std.Trim(first=1), plane=plane)

    def _set_sc_props(n: int, f: list[vs.VideoFrame]) -> vs.VideoFrame:
        fout = f[0].copy()
        fout.props['_SceneChangePrev'] = int(float(f[1].props.get('PlaneStatsDiff', 0.0)) > threshold)
        fout.props['_SceneChangeNext'] = int(float(f[2].props.get('PlaneStatsDiff', 0.0)) > threshold)
        return fout

    return clip.std.ModifyFrame(
        clips=[clip, prev_stats, next_stats],
        selector=_set_sc_props
    )