Holding: A modifying phrase is presumed to attach to the nearest semantically plausible term, but that presumption can be overcome if the claim language, specification, or prosecution history indicates a contrary interpretation.
DivX owns US Patent No. 10,225,588 directed to systems and methods for streaming partly encrypted media content. Some streams use adaptive bitrate streaming (“ABS”) to adjust the quality of streamed media sent to a user based on network quality. To reduce unauthorized access to a stream, the media content can be protected, for example, through encryption. The ‘588 Patent states that one way to reduce the resources needed for encryption is to encrypt only parts of the streamed media and to provide decryption information and information about which portions of the stream are encrypted. Typically, in ABS systems, top-level index files are used to identify alternative media streams depending on the streaming conditions. These alternative streams are stored within container files.
Claim 1 of the ‘588 Patent recites a playback device for playing protected content from a plurality of alternative streams. This process includes “locating encryption information that identifies encrypted portions of frames of video within the requested portions of the selected stream of protected video.”
DivX sued Netflix, alleging infringement of the ‘588 Patent. Netflix challenged the validity of the ‘588 Patent in an IPR. In order to overcome prior art presented in the IPR, DivX argued that its locating step required that the encryption information be located within the requested portions of the selected stream. However, the PTAB found this construction to be too restrictive and held that the encryption information could be located anywhere, but just needed to identify encrypted portions of frames that were within the requested portions of the selected stream. Despite this construction, the PTAB still found the ‘588 Patent to be patentable based on a lack of expected success in combining Netflix’s prior art. Netflix appealed, and the Federal Circuit remanded. On remand, the PTAB changed its construction and switched to the construction argued by DivX, which required the encryption information to be located within the requested portion of the stream.
The Federal Circuit found the PTAB’s acceptance of DivX’s proposed construction to be erroneous. The precepts of English grammar must be used to determine the ordinary meaning of the “locating” phrase that is present in claim 1 of the ‘588 Patent. This phrase can have two possible interpretations. The modifier “within the requested portions of the selected stream of protected video” could apply to either “encrypted portions of frames of video” or “encryption information” to specify the location either of the frames of video or the encryption information.
As a general rule, when no commas or other signals are used, a modifying phrase is presumed to attach to the nearest grammatically plausible term. In this case, that means that the phrase “within the requested portions of the selected stream of protected video” modifies “encrypted portions of frames of video” rather than “encryption information.” Therefore, the encryption information is not required to be within the requested portion of the protected video as suggested by DivX’s construction.
This general rule only creates a presumptive interpretation for claim construction and can be overridden if there is some indication within the claim or the specification that another construction should apply. In this case, claim 1 of the ‘588 Patent supports the interpretation that the encryption information is not required to be within the requested portion of the video. Claim 1 recites “decrypting . . . each encrypted portion of the frames of video” and then “playing back the decrypted frames of video.” The Federal Circuit found that nothing about these limitations requires or suggests that the encryption information must be found within the requested portions of the selected stream of video.
The Federal Circuit also looked to the specification of the ‘588 Patent to confirm that the presumptive claim interpretation was not contradicted. Although several portions of the specification describe the encryption information as being located within the requested portions of the video, there is nothing in the specification that limits the invention to this arrangement. In some examples given in the specification, the encryption information is located in a top-level index file rather than in the container in which the selected stream is located.
The Federal Circuit also examined the prosecution history to ensure that its presumptive interpretation was correct. A parent patent to the ‘588 Patent shared the same specification as the ‘588 Patent and specifically claims that a type of encryption information is located in a top-level index file rather than being located within the requested portions of the selected streams. This further supports the presumptive interpretation of the “locating” step of claim 1 of the ‘588 Patent.
Leave a Reply