autoshot.py

# SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
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# Licensed under the Apache License, Version 2.0 (the "License");
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# http://www.apache.org/licenses/LICENSE-2.0
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"""AutoShot shot detection.

Requires `ffmpeg` installed on host.
"""

from functools import lru_cache
from pathlib import Path
from typing import Callable

import torch

from algo import utils
from algo.autoshot_pytorch import AutoShot


@lru_cache
def load_model() -> Callable[[torch.Tensor], torch.Tensor]:
    """Singleton of model."""

    model = AutoShot()
    state_dict = torch.load("algo/autoshot-pytorch-weights.pth", weights_only=True)["net"]
    model.load_state_dict(state_dict)
    model.eval().cuda()
    return model


def detect(video_path: Path, threshold: float = 0.4) -> list[tuple[int, int]]:
    """Shot detection with AutoShot."""

    model = load_model()
    frames = utils.get_frames(video_path, height=27, width=48)
    with torch.no_grad():
        predictions = utils.get_predictions(model, frames, threshold)
    scenes = utils.get_scenes(predictions)
    return scenes.tolist()