[notatoad]

On any specific technology, you absolutely can know that no one else has patents on it. That is the responsibility of the patent office: to grant exclusive rights to an 'invention'. you cannot be held liable for infringement of anything you have a license for.

In this case though, Microsoft only has patents on part of the algorithm, so it is theoretically possible that other parts of the algorithm are covered by other patents.

[prodigal_erik]

It's rare, but I remember reading that USPTO has mistakenly issued conflicting patents. Legally, any publication is enough to bar others' patents, they're just not good at finding anything in the software literature, so having your own patent sort of rubs examiners' noses in it.

[notatoad]

But the point is that if the USTPO issues conflicting patents, it is them that is liable instead of you. If you have a license, you're golden.

[azakai]

> On any specific technology, you absolutely can know that no one else has patents on it. That is the responsibility of the patent office: to grant exclusive rights to an 'invention'.

The problem though is that anything complex like a video or audio codec can constitute many "inventions" from the USPTO's point of view. H.264 has many patents on it, for example. Again, this is one of the big problems with the current patent system.

So in practical terms you can never use a codec with the knowledge that no one else has patents on it.