Netflix, Inc. v. DivX, LLC presents a deceptively simple question of grammar that ultimately determined the fate of an inter partes review. In a precedential opinion authored by Judge Taranto, the Federal Circuit reversed the Patent Trial and Appeal Board’s claim construction, vacated its final written decision, and remanded for further proceedings.
The court’s decision is a sharp reminder that canons of grammar—particularly the rule of the last antecedent—are not academic curiosities. They can decide whether a claim survives or falls. And here, they did.
The Technology: Partial Encryption in Adaptive Bitrate Streaming
DivX’s U.S. Patent No. 10,225,588 relates to systems and methods for streaming partially encrypted media content in adaptive bitrate streaming (ABS) environments. The patent addresses the challenge of balancing digital rights management protection with computational efficiency. Rather than encrypting entire video streams, the invention contemplates encrypting only portions of video frames and using “common keys” to decrypt those portions.
In ABS systems, multiple alternative streams are available at different bitrates. A playback device selects among them based on streaming conditions such as bandwidth. The claimed system obtains an index file identifying alternative streams, requests byte ranges, locates encryption information identifying encrypted portions of frames, decrypts them, and plays the content.
The claim language at issue was limitation [l] of claim 1:
locating encryption information that identifies encrypted portions of frames of video within the requested portions of the selected stream of protected video.
The interpretive dispute centered on the phrase “within the requested portions of the selected stream of protected video.” Did that modifier apply to:
- the “encrypted portions of frames of video,” or
- the “encryption information”?
The answer dictated whether the prior art satisfied the limitation.
The Procedural Path: Two Board Decisions, One Federal Circuit Reset
After DivX sued Netflix for infringement, Netflix petitioned for IPR, asserting obviousness over Chen in view of Lindahl and Hurst. The Board instituted review.
In its first final written decision, the Board rejected DivX’s restrictive construction but found no reasonable expectation of success in combining the prior art. The Federal Circuit vacated that determination in 2023 and remanded.
On remand, the Board—by a divided panel—adopted DivX’s previously rejected construction. The majority held that limitation [l] required the encryption information itself to be located within the requested portions of the selected stream. Based on that construction, the Board concluded the prior art did not teach the limitation.
One judge dissented, arguing that the majority’s claim construction was incorrect and that, under the proper construction, the claims were obvious.
Netflix appealed again. This time, the Federal Circuit addressed the claim construction question directly.
The Core Issue: Grammar as Law
The Federal Circuit began with a straightforward acknowledgment: the claim language was susceptible to two syntactically plausible interpretations. The modifier could attach to either possible referent.
When confronted with such ambiguity, courts do not guess. They turn to established interpretive principles. Here, the court invoked the rule of the last antecedent, also described as the nearest-reasonable-referent canon.
As articulated in cases such as Lockhart v. United States and Finisar Corp. v. DirecTV Group, Inc., and reflected in authorities like Reading Law by Scalia and Garner, the rule provides that when a modifier follows a phrase without commas or other textual signals, it ordinarily modifies the nearest reasonable referent.
Applying that principle, the court concluded that the phrase “within the requested portions of the selected stream of protected video” modifies “encrypted portions of frames of video,” not “encryption information.”
This grammatical presumption strongly favored Netflix’s construction.
Intrinsic Evidence: Claims, Specification, and Prosecution History
The Federal Circuit did not stop at grammar. It conducted the familiar Phillips v. AWH Corp. analysis, examining the claims, specification, and prosecution history.
Claim Context
Under Netflix’s interpretation, limitation [l] requires the processor to locate encryption information that identifies encrypted portions that are within the requested portions. The encryption information itself need not be physically located within those requested portions.
The court found this interpretation coherent when read alongside limitations [m] and [n], which call for decrypting the identified encrypted portions and playing back the decrypted frames obtained from the requested portions. Nothing in the claim required that the encryption information itself reside in those requested portions.
Importantly, limitation [c] requires obtaining a “top level index file.” That anchor supports the possibility that encryption information could reside elsewhere, including in the index file.
Specification
DivX argued that the specification described embodiments where encryption information was located within the requested portions.
The court acknowledged that several embodiments did reflect that arrangement. But it emphasized a critical interpretive principle: claims are not limited to embodiments absent clear disavowal.
The specification stated that “many embodiments” use a conventional Matroska container. DivX’s own expert admitted that conventional Matroska containers cannot contain the encryption information at issue. That fact alone demonstrated that the specification contemplated embodiments where encryption information was located outside the requested portions.
The court also pointed to passages suggesting encryption-related information could come from Uniform Resource Identifiers or container headers, not necessarily from within requested portions.
Under Pitney Bowes, Inc. v. Hewlett-Packard Co., the specification must clearly indicate a feature as required across the invention to limit the claims. That was not the case here.
Prosecution History
The prosecution history provided additional reinforcement. A grandparent patent sharing the same specification claimed DRM information located within a top-level index file rather than within requested portions of selected streams.
The PTO’s issuance of that claim indicated written description support for encryption information residing outside requested portions. That further undercut DivX’s restrictive reading.
The Holding
The Federal Circuit reversed the Board’s claim construction, holding that:
- It is the “encrypted portions” of frames of video—not the “encryption information”—that must be located within the requested portions of the selected stream.
- Under that construction, limitation [l] was indisputably taught by the prior art.
- The Board’s final written decision was vacated and remanded.
Costs were awarded to Netflix.
Why This Decision Matters
This case is not about adaptive bitrate streaming. It is about disciplined claim construction.
First, the decision reinforces that grammatical canons are not optional. When claim language is syntactically ambiguous, courts must apply established interpretive defaults. The rule of the last antecedent remains alive and powerful.
Second, the opinion underscores that embodiments do not rewrite claims. Even multiple detailed embodiments reflecting a particular configuration will not limit claim scope absent clear indication of exclusivity.
Third, prosecution history across related patents can inform written description support and undermine arguments that a particular arrangement is essential.
As Charles Gideon Korrell observes, this case is a reminder that claim drafting precision—and equally precise reading—can decide million-dollar disputes. A single modifier can swing the obviousness analysis.
Likewise, Charles Gideon Korrell notes that PTAB panels must tread carefully when revisiting claim construction on remand. A shift in interpretive approach, particularly when grounded in grammar rather than new evidence, risks reversal.
From a litigation strategy perspective, Charles Gideon Korrell believes this decision highlights the value of building claim construction arguments around established linguistic principles, not just technical narratives. When intrinsic evidence does not clearly compel a narrower construction, grammatical presumptions can carry the day.
Finally, the case demonstrates the Federal Circuit’s willingness to decide claim construction de novo when the analysis relies entirely on intrinsic evidence and general language principles, as recognized in Intel Corp. v. Qualcomm Inc. and SIMO Holdings Inc. v. Hong Kong uCloudlink Network Technology Ltd..
Takeaway
Netflix v. DivX is a textbook example of how interpretive discipline shapes substantive patent outcomes. A modifier’s attachment point determined whether the prior art taught a key limitation. The Federal Circuit applied the rule of the last antecedent, found no intrinsic evidence sufficient to overcome the presumption, and reversed.
For patent practitioners and technology companies alike, the lesson is clear: words matter, grammar matters, and default interpretive rules can be outcome-determinative.









