feat(hardcode-subs): add subtitle burn-in helper

hardcode_subs.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env -S python3.12
+
+from pathlib import Path
+import logging
+import subprocess
+import argparse
+
+logger = logging.getLogger(__name__)
+
+
+def hardcode_subs(
+    video_path: Path,
+    subtitle_path: Path,
+    lang: str,
+    save_path: Path | None = None,
+    resolution: str | None = None,
+    quality: float | None = None,
+    font_size: int = 40,
+) -> Path:
+    if not save_path:
+        save_path = video_path.with_name(f"{video_path.stem}.{lang}.hardcoded.mp4")
+    vf_filters = [f"subtitles='{subtitle_path}:force_style=Fontsize={font_size}'"]
+    if resolution:
+        resolution_map = {"1080p": 1920, "720p": 1280, "480p": 854}
+        max_width = resolution_map.get(resolution)
+        if max_width:
+            vf_filters.append(f"scale='min({max_width},iw)':-2")
+    vf = ",".join(vf_filters)
+    crf = str(quality) if quality else "35"
+    cmd = [
+        "ffmpeg",
+        "-y",
+        "-hwaccel",
+        "videotoolbox",
+        "-i",
+        str(video_path),
+        "-vf",
+        vf,
+        "-c:v",
+        "h264_videotoolbox",
+        "-crf",
+        crf,
+        "-c:a",
+        "copy",
+        str(save_path),
+    ]
+    logger.info(f"Hardcoding subtitles into video: {save_path.name}")
+    subprocess.run(cmd, check=True)
+    return save_path
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description="Hardcode subtitles into a video.", formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+    parser.add_argument("video", type=Path, help="Path to the video file")
+    parser.add_argument("subtitle", type=Path, help="Path to the subtitle file")
+    parser.add_argument("--out", "-o", type=Path, help="Path to the output video file")
+    parser.add_argument("--lang", default="en", help="Language code for subtitles")
+    parser.add_argument(
+        "--resolution",
+        choices=["1080p", "720p", "480p"],
+        help="Set output video resolution (max width)",
+    )
+    parser.add_argument(
+        "--quality",
+        "-q",
+        type=float,
+        default=35,
+        help="Set CRF quality factor (lower is better, default 35)",
+    )
+    parser.add_argument(
+        "--font-size",
+        type=int,
+        default=40,
+        help="Font size for hardcoded subtitles",
+    )
+    return parser.parse_args()
+
+
+def main():
+    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s: %(message)s")
+    args = parse_args()
+    if not args.video.exists():
+        raise FileNotFoundError(f"Video file not found: {args.video}")
+    if not args.subtitle.exists():
+        raise FileNotFoundError(f"Subtitle file not found: {args.subtitle}")
+
+    save_path = args.out or args.video.with_name(f"{args.video.stem}.{args.lang}.hardcoded.mp4")
+    hardcoded_video = hardcode_subs(
+        video_path=args.video,
+        subtitle_path=args.subtitle,
+        lang=args.lang,
+        save_path=save_path,
+        resolution=args.resolution,
+        quality=args.quality,
+        font_size=args.font_size,
+    )
+    logging.info(f"Hardcoded video saved at: {hardcoded_video}")
+
+
+if __name__ == "__main__":
+    main()