feat: compress downloads to max 250MB via ffmpeg

app.py

@@ -3,7 +3,9 @@
 
 from __future__ import annotations
 
+import json
 import os
+import subprocess
 
 from dotenv import load_dotenv
 from flask import (
@@ -204,6 +206,41 @@ def jobs_list():
     return render_template("jobs.html", jobs=jobs)
 
 
+def _compress_for_download(file_path: str, max_bytes: int = 250 * 1024 * 1024) -> str | None:
+    """Compress file_path with ffmpeg if larger than max_bytes.
+
+    Returns path to `<name>_compressed.mp4` next to the input, or None to
+    fall back to the original file (small file, ffmpeg missing/failed).
+    """
+    if not os.path.isfile(file_path):
+        return None
+    if os.path.getsize(file_path) <= max_bytes:
+        return None
+    out_path = os.path.splitext(file_path)[0] + "_compressed.mp4"
+    if os.path.isfile(out_path):
+        return out_path
+    try:
+        probe = subprocess.run(
+            ["ffprobe", "-v", "quiet", "-print_format", "json", "-show_format", file_path],
+            capture_output=True, text=True, timeout=60,
+        )
+        duration = float(json.loads(probe.stdout).get("format", {}).get("duration") or 0)
+    except (OSError, subprocess.SubprocessError, ValueError, TypeError, AttributeError):
+        return None
+    if duration <= 0:
+        return None
+    bitrate = int((max_bytes * 8 * 0.92) / duration)
+    try:
+        subprocess.run(
+            ["ffmpeg", "-y", "-i", file_path, "-c:v", "libx264",
+             "-b:v", str(bitrate), "-c:a", "aac", "-b:a", "64k", out_path],
+            capture_output=True, timeout=3600, check=True,
+        )
+    except (OSError, subprocess.SubprocessError):
+        return None
+    return out_path if os.path.isfile(out_path) else None
+
+
 @app.route("/download/<job_id>/<filename>")
 def download(job_id, filename):
     job = job_queue.get_job(job_id)
@@ -216,7 +253,8 @@ def download(job_id, filename):
         return "File not found", 404
     if not os.path.isfile(file_path):
         return "File not found", 404
-    return send_file(file_path, as_attachment=True)
+    compressed = _compress_for_download(file_path)
+    return send_file(compressed or file_path, as_attachment=True)
 
 
 @app.route("/api/videos")