The MP4 container is the most ubiquitous video format in the world. It is commonly used with the H.264 video codec, of which there has been a lot written about when the patents for this codec will expire. The last of the baseline patents, we think, will expire by the end of 2027.

The H.264 codec, however, is also commonly used together with AAC audio codec in the MP4 container. I've done some research on the patents for this codec, but I can't find much. The best I could find was this forum post.

AAC was first standardized in 1997, but has received many updates since. There are two main categories of patents as they relate to codecs:

  1. Baseline Patents
  2. Extension Patents

The first category, Baseline Patents, refers to those patents which are necessary to implement AAC encoders and decoders at all. The second category includes extensions that aren't necessary to implement encoders or decoders for the codec, but users might expect or are otherwise useful. I'm only interested in the baseline patents.

The goal here is to discover the first practical date for conveying a H.264/AAC encoder/decoder to users, for example with Fedora shipping these encoders/decoders with their free builds of ffmpeg. These libraries can then be used by media players like VLC to decode media encoded in these formats.

It's worth mentioning that it's possible some of these patents are actually invalid and may be challenged in court, and thus expire earlier. It's also possible that the significant patent holders for AAAC will join an organization like Alliance for Open Media and "donate" their patents to be used royalty-free by anyone. These unlikely scenarios occurring would also satisfy the goal I mentioned above. But I'm not particularly interested in initiatives like Openh264 from Cisco.

Edit: That being said, it would be useful to know what the most common profile used for encoding with AAC is currently. There are a few:

  • Main Audio Profile – defined in 1999, uses most of the MPEG-4 Audio Object Types (AAC Main, AAC-LC, AAC-SSR, AAC-LTP, AAC Scalable, TwinVQ, CELP, HVXC, TTSI, Main synthesis)
  • Scalable Audio Profile – defined in 1999, uses AAC-LC, AAC-LTP, AAC Scalable, TwinVQ, CELP, HVXC, TTSI
  • Speech Audio Profile – defined in 1999, uses CELP, HVXC, TTSI
  • Synthetic Audio Profile – defined in 1999, TTSI, Main synthesis
  • High Quality Audio Profile – defined in 2000, uses AAC-LC, AAC-LTP, AAC Scalable, CELP, ER-AAC-LC, ER-AAC-LTP, ER-AAC Scalable, ER-CELP
  • Low Delay Audio Profile – defined in 2000, uses CELP, HVXC, TTSI, ER-AAC-LD, ER-CELP, ER-HVXC
  • Low Delay AAC v2 - defined in 2012, uses AAC-LD, AAC-ELD and AAC-ELDv2[45]
  • Mobile Audio Internetworking Profile – defined in 2000, uses ER-AAC-LC, ER-AAC-Scalable, ER-TwinVQ, ER-BSAC, ER-AAC-LD
  • AAC Profile – defined in 2003, uses AAC-LC
  • High Efficiency AAC Profile – defined in 2003, uses AAC-LC, SBR
  • High Efficiency AAC v2 Profile – defined in 2006, uses AAC-LC, SBR, PS
  • Extended High Efficiency AAC xHE-AAC – defined in 2012, uses USAC
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    A more accurate answer beyond adding 20 years from the spec publication date is going to require somebody to look at over 800 patents in the pool while being an expert in patent law of 26 jurisdictions, according to the Excel you linked. Also, there's no requirement of joining the pool, you have to go back to ISO process. I'm sure a firm has done it, and somebody has paid probably 6 digits for it. You're now asking which ones are invalid, and there's the possibility that somebody else outside the standards process holds relevant patents... that's going to add a factor of 10-100 to that cost.
    – user71659
    Oct 10, 2023 at 6:05
  • Ah yes, I completely forgot about patents not being included in the pool. Well, that's fun to consider. To be honest, I wasn't actually expecting a complete (or accurate) answer, but I know there is context I'm missing here. For instance, it's possible that some of these profiles are actually not patent-encumbered because they've expired? I'm not sure! I tried to limit the scope to baseline patents to make this a little more reasonable. Anyway, I think your comment was very valuable if only to explain how ridiculously hard it is to answer this question. I didn't know all that.
    – ripandtear
    Oct 10, 2023 at 7:12
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    the comment by @user71659 is exemplary why this question is far too broad and unfocussed. A professional lawyer would tell you to either just buy a license or bill you millions to dissect that.
    – Trish
    Oct 10, 2023 at 11:29
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    On the subject of buying a license—it's not actually an option for Fedora. They'd need to negotiate some sort of unlimited license deal (and they don't have the money to do that). I think the question itself is quite simple and narrow: when will the baseline patents for AAC expire? Further context on why I want to know is because it's often used with H.264. The rest could be cut out and not change the core of the question. But I do recognize this question is impossible to answer without serious resources and time nobody is going to invest for free. So closing the question seems reasonable.
    – ripandtear
    Oct 10, 2023 at 12:33
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    @GeorgeWhite That's the nominal term of validity. The issue is extensions, which can add years in the US. Right now, 20% are exceeding 3 years in processing and thus subject to extension. Add in differing policies from other countries and it becomes a much more complicated problem. (I've heard in multiple cases Malaysian patents end up being many years longer than the rest)
    – user71659
    Oct 10, 2023 at 18:22


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