Chess’s Knight forces a Checkmate and Leads to a Strong Prior-Art

As prior-art searchers, we perform complex prior-art searches everyday. But at times we stumble upon some cases that result in truly amazing experiences and takeaways.
We performed an invalidation search on a European patent - the technology of the target patent was related to the motion vector prediction technique in the video’s encoding/ decoding domain.
We started the invalidation search by thoroughly understanding the invention and the file history documents to deduce the novelty of the claimed invention. The next step involved the identification of the related keywords, classifications, and prominent assignees/inventors.

As a general practice, it is important to understand that the terms used in patents are sometimes quite different from the terms used in other documents like journals, white papers, technical manuals, or research articles. It is very important to have a detailed set of relevant terms/keywords before starting with a search.

The most common employed method in patent search is the use of narrower terms i.e. hyponyms to execute a targeted search. It is followed by the use of synonyms of the search terms and then by the use of broader terms i.e. hypernyms.

In this case, our analysis was targeted at the novel feature of the independent claim – A decoder calculates a motion vector predictor (MVP) for the current block from the MVP candidates stored in an MVP candidate list buffer, wherein

- the MVP candidates in the MVP candidate list buffer includes at least one MVP candidate that is a motion vector of a non-adjacent block and

- the non-adjacent block is non-adjacent to the current block of the current picture.

After studying the documents, a nomenclature table was prepared for the project that included the synonyms, hypernyms and hyponyms for the search vocabulary. These were the synonyms that were generated from the references analyzed in the keyword association-based search. For example, the keyword of interest here is:

Non-adjacent - non-neighbouring, non-neighboring, non-successive, non-contiguous, non-immediate, farther, remote, distant

Using the above terms, we developed our search strategy and initiated the search and analysis process. We executed various strategies such as - spider/ citation search, classification (CPC, IPC, US, F-terms, FI) search, assignee/ inventor based search, similarity and semantic search. Then, we explored the non-patent databases to discover potential references other than patents.

Further, many patent databases provide a feature of highlighting keywords employed in the search strings and the analyst normally goes through the highlighted keywords only. But considering this case, the term non-adjacent was not clearly specified in the results.

So, our researcher decided to not just read the highlighted keywords but also have a look at the figures/images as well. This strategy revealed an interesting reference in which the term “next knight’s order” was mentioned. It is noteworthy to observe that the term “non-adjacent” was not directly written anywhere in the reference but it was explained in reference in relation to a move of a chess knight piece.

Finally, we succeeded in identifying a category X reference that was close to the inventive step and was published before the effective filing date of the target patent. The identified reference disclosed the process of determining the motion vector predictor of the current block using a non-adjacent block, but the methodology uses a unique term to divulge the concept of the non-adjacent block. The macroblock processing pipeline method explained in the identified reference was “Knight’s order processing” in a quad row in which the knight moves one row down and two columns to the left such that it provided one or more stages (e.g. four stages) of spacing between adjacent blocks in the pipeline (can be seen in the figure below).


Prior-art search is an enigma in itself and there is no fixed strategy to locate strong results. As an IP researcher, it is very important to keep your thought process aligned to a broader perspective of technology and look out for concepts that can be camouflaged differently. To put it simply, sometimes the results are right there in front of our eyes but we just need the right perspective to recognize them as important results. In this case, we employed the aforesaid techniques and eventually identified a very strong prior-art result for our Client - he was extremely happy with our out-of-box thought process.

At Expertlancing, we have worked on numerous complex prior-art searches encompassing diverse technical areas. We always employ innovative processes to deliver the best results – you can reach out to us for more information.

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