FAQ
1. Is Alchemist free?
Yes. Alchemist is GPLv3 open source.
2. Will it ruin my quality?
No by default. The planner uses BPP analysis and optional VMAF gating to avoid pointless or low-quality transcodes.
3. How much space will I save?
Typical results are 30–70%, depending on source quality, codec choice, and how much waste is in the original file.
4. Do I need a GPU?
No. CPU encoding works. GPU encoding is much faster and more power-efficient.
5. Does it work with Plex, Jellyfin, or Emby?
Yes. Point Alchemist at the same media directories your server already uses.
6. What happens to my originals?
By default they stay in place. Nothing is deleted unless you
enable delete_source.
7. Does it support 4K and HDR?
Yes. It can preserve HDR metadata or tonemap to SDR.
8. Can I run multiple instances?
Not against the same SQLite database. Use one Alchemist instance per DB.
9. What is BPP?
Bits-per-pixel. It is the compression density measurement Alchemist uses to decide whether a file is already efficient.
10. What is VMAF?
Netflix’s perceptual quality metric. It is optional and slows down post-encode validation.
11. How do I update?
docker compose pull && docker compose up -d
12. What if hardware is not detected?
CPU fallback is automatic unless you disabled it. Check the hardware probe log to fix the GPU path.
13. Can I control when it runs?
Yes. Use Settings → Schedule to define allowed windows.
14. Does it handle subtitles?
Yes. Subtitle mode supports copy, burn, extract, and drop.
15. Why did it skip my file?
Open the skipped job and read the reason, or start with Skip Decisions.