A patent battle between Microsoft and Google-owned Motorola Mobility was brought one step closer to resolution this week when a US District Court judge threw out 13 of the patent claims Motorola made in the case.

It is far from a crippling blow to Motorola, however. Judge James Robart of US District Court in Seattle is tasked with deciding what is a "fair and reasonable" rate for the license fees Microsoft should pay Motorola for use of patents tied to H.264 video and Wi-Fi standards. Microsoft proposed a payment of $1.21 million per year to Motorola, but Motorola demanded 2.25 percent of the sale price of Windows PCs and Xbox 360s, which Microsoft has said could amount to billions. While Motorola sued Microsoft for patent infringement, Microsoft also sued Motorola for not meeting its obligation to license standards-essential patents at fair and reasonable rates, leading to multiple court cases being consolidated into one.

While the case as a whole could have far-reaching consequences, the latest development is minor in comparison. Motorola claimed that three video patents (here, here, and here) related to encoding and decoding digital video are infringed by Windows 7 and Internet Explorer 9. These make up just a subset of the 16 video patents asserted by Motorola against Microsoft in this case, and the judge didn't kill the three patents completely. While Robart dismissed 13 claims, there were 32 overall.

Robart's order granting Microsoft's motion for partial summary judgment (PDF) agreed with Microsoft's contention "that the 'means for decoding' and 'means for using' elements recited in the Claims-at-Issue are invalid as indefinite because the Patents-in-Suit do not adequately describe a corresponding structure." The decision, written Wednesday and posted publicly yesterday, related just to the video patents in the case, not the wireless ones.

There's no scheduled date for the big decision that will determine how much money Microsoft has to pay Motorola, but Microsoft has told Ars it expects the verdict to come down in late February or March. To learn more about the case, read our pre-trial explainer.