All worldwide patents have expired except for 3 Brazilian patents. For historical reference:
- last European patent, EP 1279291, expired on 2021-04-09;
- last meaningful US patent, US 6959046, expired on 2022-12-07. The last US patent, likely non essential, US 7395211, expired on 2023-11-14.
The patent list managed by Via Licensing Alliance is available at: https://www.via-la.com/licensing-2/mpeg-4-visual/mpeg-4-visual-patent-list/
This is about MPEG-4 Part 2 (for example Xvid). For H.264 or AVC see Have the patents for H.264 MPEG-4 AVC expired yet?
MPEG-4 Visual has these 3 active patents in Brazil:
- BR PI0113271-7 (Dolby Laboratories Licensing Corporation) - this patent that was added to the pool in April 2021 is (not legal advice) likely non essential. It describes some methods to hide data in an audio or video stream with lossy compression. It can be used with MPEG-1, MPEG-2 and MPEG-4 for video and various audio codecs including MP3 and AAC. This is about watermarking. The watermarking process involves messing with the encoder, slightly distorting output.
- BR PI0109962-0 (Siemens AG)
- BR PI9904785-3 (Sun Patent Trust)