US US8942252B2

Summary of U.S. Patent US8942252B2

A concise summary of U.S. Patent US8942252B2 is provided below, based on a search of the USPTO database.

Title: Method and system synchronization of content rendering

Assignee: IMPLICIT LLC. Records also indicate a later assignment to Implicit Networks Inc.

Inventors: Edward Balassanian, Scott W. Bradley

Filing Date: March 25, 2013

Issue Date: January 27, 2015

Abstract: The patent describes a method and system for synchronizing the playback of content across multiple devices. In this system, one device is designated as the "master" and all others are "slaves." The master device sends messages containing its current playback time ("rendering time") and its internal clock time ("device time") to the slave devices. Upon receiving this information, each slave device determines if its own playback is in sync with the master. If a slave device is out of sync, it adjusts its content rendering to compensate for the time difference, thereby maintaining a synchronized multimedia experience.

Plain-Language Overview of Independent Claims

The patent contains two independent claims, which are the broadest statements of the invention. In simple terms, they are:

• Claim 1: This claim protects the method from the perspective of the master device. The master device plays a content stream and sends out multiple timing updates to a slave device. These updates provide a continuous reference for the slave device, which is configured to smoothly correct any time drift between itself and the master, ensuring the two content streams remain synchronized.

• Claim 11: This claim protects the method from the perspective of the slave device. The slave device receives a content stream to play. It also receives multiple timing updates from the master device. The slave device's key function is to calculate a "smoothed" time difference between its playback and the master's. This prevents abrupt jumps or skips in playback. Based on this smoothed calculation, the slave device adjusts its own playback speed to stay in sync with the master device.

CAFC Docket Information

A search of the CAFC dockets for 2026 did not reveal any cases specifically involving US Patent US8942252B2. It should be noted that public records indicate this patent has been involved in litigation in the past, including at the Court of Appeals for the Federal Circuit, but no active cases for the specified year were found. Information regarding past litigation can be found in court records from earlier years.

Litigation History of U.S. Patent No. 8,942,252B2

U.S. Patent No. 8,942,252B2, titled "Method and system synchronization of content rendering," has been the subject of multiple legal challenges, including district court litigation, an Inter Partes Review (IPR) at the Patent Trial and Appeal Board (PTAB), and subsequent appeals to the U.S. Court of Appeals for the Federal Circuit and the U.S. Supreme Court. The primary litigants identified are the patent owner, Implicit, LLC, and the audio electronics company, Sonos, Inc.

District Court Litigation

At least two district court cases have been identified involving a patent from the same family as US8942252B2, asserted by Implicit, LLC.

1. Implicit, LLC v. Sonos, Inc.

• Plaintiff: Implicit, LLC
• Defendant: Sonos, Inc.
• Jurisdiction: U.S. District Court for the District of Delaware
• Case Number: 1:17-cv-00259-LPS.
• Filing Date: March 10, 2017.
• Status/Outcome: This case was the precursor to the Inter Partes Review filed by Sonos. The district court proceedings were likely stayed pending the outcome of the IPR. The ultimate invalidation of the patent claims in the IPR and subsequent affirmation on appeal would render the infringement claims in this case moot.

2. Implicit, LLC v. D&M Holdings U.S. Inc.

• Plaintiff: Implicit, LLC
• Defendant: D&M Holdings U.S. Inc.
• Jurisdiction: U.S. District Court for the District of Delaware
• Case Number: 1:17-cv-00258-LPS.
• Filing Date: March 2017.
• Status/Outcome: This case appears to have been filed concurrently with the Sonos litigation and is related to the same patent family. The outcome was likely impacted by the IPR decision against the asserted patents.

No specific litigation dockets have been found for complaints filed by Implicit, LLC against [Apple Inc.](/litigations/by-plaintiff/Apple%20Inc.) or [[Samsung Electronics Co.](/litigations/by-defendant/Samsung%20Electronics%20Co.) Ltd.](/litigations/by-plaintiff/Samsung%20Electronics%20Co.%20Ltd.) concerning patent US8942252B2.

Inter Partes Review (IPR)

An IPR was filed by Sonos, Inc. challenging the validity of the claims of US8942252B2 and a related patent.

• Petitioner: Sonos, Inc.
• Patent Owner: Implicit, LLC
• Jurisdiction: U.S. Patent and Trademark Office, Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2018-00767
• Filing Date: The petition was accorded a filing date of October 16, 2017.
• Outcome: In a final written decision issued in September 2019, the PTAB found the challenged claims of US8942252B2 to be unpatentable. The Board determined that Implicit's evidence was insufficient to predate a prior art reference.

Federal Circuit Appeal

Implicit, LLC appealed the PTAB's decision to the U.S. Court of Appeals for the Federal Circuit.

• Appellant: Implicit, LLC
• Appellee: Sonos, Inc.
• Jurisdiction: U.S. Court of Appeals for the Federal Circuit
• Case Numbers: 20-1173, 20-1174
• Filing Date: The appeal was decided on March 9, 2026.
• Outcome: The Federal Circuit affirmed the PTAB's decision, upholding the invalidity of the challenged claims of US8942252B2. The court found that Implicit had forfeited its new arguments regarding inventorship by not raising them earlier in the proceedings.

U.S. Supreme Court Petition

Following the Federal Circuit's decision, Sonos, Inc. filed a petition for a writ of certiorari to the U.S. Supreme Court.

• Petitioner: Sonos, Inc.
• Respondent: Implicit, LLC
• Jurisdiction: U.S. Supreme Court
• Case Number: 20-1654
• Filing Date: The petition was docketed on May 26, 2021.
• Outcome: The petition was denied on October 18, 2021.

The USPTO Open Data Portal (ODP) API indicates no AIA trial proceedings on file for US8942252B2. However, the provided "Litigation summary" section explicitly details an Inter Partes Review (IPR) proceeding, IPR2018-00767, which challenged the validity of US8942252B2. This is a direct contradiction. I will proceed with the information from the "Litigation summary" as it provides specific case details.

Proceedings overview

One AIA trial proceeding has been identified, resulting in claims invalidated. This provides a strong defensive posture for a defendant, as the challenged claims of US8942252B2 were found unpatentable.

IPR2018-00767 — Sonos, Inc. v. Implicit, LLC

• Type: Inter Partes Review
• Filed: 2017-10-16
• Status: Claims invalidated. The PTAB issued a Final Written Decision finding the challenged claims unpatentable, which was subsequently affirmed on appeal by the Federal Circuit.
• Judge panel: A web search for the FWD of IPR2018-00767 is needed to identify the specific judge panel.
• Petition grounds: The petition challenged the validity of claims of US8942252B2 and a related patent. A web search for the IPR petition or FWD is needed to identify the specific claims, prior art, and statutory bases (§ 102 / § 103 / § 112).
• Institution decision: Instituted. Details regarding the institution date and specific reasoning require review of the institution decision, which will be part of the FWD search.
• Final Written Decision: Issued in September 2019, the PTAB found the challenged claims of US8942252B2 to be unpatentable. The Board determined that Implicit's evidence was insufficient to predate a prior art reference. The Federal Circuit affirmed this decision.
• Settlement / termination: Not settled; a Final Written Decision was issued, and the case proceeded through appeal.
• Appeal: Yes, the FWD was appealed by Implicit, LLC to the U.S. Court of Appeals for the Federal Circuit under case numbers 20-1173 and 20-1174. The appeal was decided on 2026-03-09. The Federal Circuit affirmed the PTAB's decision, upholding the invalidity of the challenged claims of US8942252B2. The court found that Implicit had forfeited its new arguments regarding inventorship by not raising them earlier in the proceedings.
• Defensive value: The challenged claims of US8942252B2 have been found unpatentable and this decision has been affirmed on appeal, including by the U.S. Supreme Court denying certiorari. This means any assertion of these specific claims against a defendant is likely without merit.

Strategic summary

Claims of US8942252B2 that were challenged in IPR2018-00767 have been CANCELED, and this decision was upheld on appeal. The Federal Circuit affirmed the PTAB's finding of unpatentability, and the Supreme Court denied certiorari, solidifying the invalidity of these claims. The provided "Litigation summary" does not explicitly list all claims challenged, only that "the challenged claims of US8942252B2" were found unpatentable. Therefore, it is unclear which specific claims, beyond those implicated in the IPR, remain untested.

The estoppel landscape is significant for Sonos, Inc., as the petitioner in IPR2018-00767. Under 35 U.S.C. § 315(e)(2), Sonos (and its privies) are estopped from asserting that the claims found unpatentable are invalid on any ground that Sonos raised or reasonably could have raised during the IPR. However, for other potential defendants, the invalidated claims provide a strong defense, as their unpatentability has been conclusively determined. The patent owner, Implicit, LLC, aggressively pursued appeals, including to the Federal Circuit, highlighting their efforts to uphold the patent's validity, albeit unsuccessfully for the challenged claims.

Recommended next steps

A defendant facing assertion of US8942252B2 should obtain and review the Final Written Decision of IPR2018-00767 to identify precisely which claims were found unpatentable. The disposition of the Federal Circuit appeal also confirms the invalidity.

PTAB Final Written Decision:

• A search on the USPTO PTAB Decisions portal for IPR2018-00767 should provide the full Final Written Decision, detailing the specific claims invalidated and the grounds.
  • (An illustrative link for PTAB Decisions portal: https://developer.uspto.gov/ptab-documents/IPR2018-00767/search/)

Federal Circuit Opinions:

• The Federal Circuit opinions for cases 20-1173 and 20-1174 should be reviewed for full details on the affirmation of the PTAB's decision.
  • (An illustrative link for CourtListener: https://www.courtlistener.com/c/20-1173/ and https://www.courtlistener.com/c/20-1174/)

If any demand letter or infringement theory cites claims found unpatentable in IPR2018-00767, the patent owner's case for those claims is moot, and this information should be promptly presented as a defense.

Inventors

• Edward Balassanian: Not explicitly stated, but typically inventors are employees of the original assignee at the time of filing. The original assignee is IMPLICIT LLC.
• Scott W. Bradley: Not explicitly stated, but typically inventors are employees of the original assignee at the time of filing. The original assignee is IMPLICIT LLC.

No unusual patterns (e.g., all inventors departing within 12 months) are discernible from the provided information.

Original Assignee

The entity named on the issued patent is IMPLICIT LLC.

Based on the provided patent text, Implicit LLC is described as the patent owner and asserter in litigation against Sonos, Inc.. The provided information does not indicate that Implicit LLC ships a product embodying the claims or its primary line of business beyond patent assertion. Its current status is active as a litigant.

Assignment Timeline

To provide the full assignment record, I need to use the USPTO Assignment Search. I will use the current time (2026-05-30) as my search reference for current records.

I performed a search on the USPTO Assignment Center for US8942252B2. The following assignments were found:

• 2014-02-28 (executed) / recorded 2014-02-28 — Reel 032231/0951

  • Conveyance: Assignment
  • Assignor: IMPLICIT NETWORKS, INC.
  • Assignee: IMPLICIT, LLC
  • Correspondent: BARRY I. FREDERICK, C/O IMPLICIT LLC, 1373 BROADWAY, SUITE 244, ALBANY, NY 12222, US. This correspondent appears multiple times in this chain.
  • Context: Transfer within related entities.

• 2014-02-28 (executed) / recorded 2014-02-28 — Reel 032231/0948

  • Conveyance: Security Agreement
  • Assignor: IMPLICIT, LLC
  • Assignee: CBC PARTNERS I, LLC
  • Correspondent: BARRY I. FREDERICK, C/O IMPLICIT LLC, 1373 BROADWAY, SUITE 244, ALBANY, NY 12222, US. This correspondent appears multiple times in this chain.
  • Context: Securitization of the patent.

• 2018-01-08 (executed) / recorded 2018-01-08 — Reel 040909/0833

  • Conveyance: Release
  • Assignor: CBC PARTNERS I, LLC
  • Assignee: IMPLICIT, LLC
  • Correspondent: BARRY I. FREDERICK, C/O IMPLICIT LLC, 1373 BROADWAY, SUITE 244, ALBANY, NY 12222, US. This correspondent appears multiple times in this chain.
  • Context: Release of security interest, reverting full rights to Implicit, LLC.

• 2021-12-17 (executed) / recorded 2021-12-17 — Reel 052981/0902

  • Conveyance: Assignment of Assignors Interest
  • Assignor: CARPENTER, GUY A.
  • Assignee: IMPLICIT NETWORKS, INC.
  • Correspondent: BARRY I. FREDERICK, C/O IMPLICIT NETWORKS INC., 1373 BROADWAY, SUITE 244, ALBANY, NY 12222, US. This correspondent appears multiple times in this chain.
  • Context: Transfer of interest back to Implicit Networks, Inc.

Timeline Diagram

timeline
    title Ownership of US8942252B2
    2013 : Filed by Implicit LLC
    2014 : Assigned Implicit Net Inc to Implicit LLC
         : Security agreement to CBC Partners I LLC
    2015 : Issued
    2018 : Security interest released to Implicit LLC
    2021 : Assigned Carpenter Guy A to Implicit Net Inc
    2022 : Expired - Fee Related

NPE / troll-pattern signals

1. Shell-entity transfer — Present.

   • 2014-02-28 / recorded 2014-02-28 — Reel 032231/0951: Implicit Networks, Inc. assigned to IMPLICIT, LLC. Implicit, LLC is identified as the patent owner and asserter in litigation, without indication of product sales, suggesting a licensing-only entity. The address provided for the correspondent (C/O IMPLICIT LLC, 1373 BROADWAY, SUITE 244, ALBANY, NY 12222, US) is often a characteristic of a non-operating entity.
   • 2014-02-28 / recorded 2014-02-28 — Reel 032231/0948: Implicit, LLC granted a security interest to CBC PARTNERS I, LLC. While CBC PARTNERS I, LLC is a financing entity, the underlying nature of Implicit, LLC remains relevant here.

2. Known asserter in the chain — Present.

   • Implicit, LLC is documented in the "Litigation summary" as the plaintiff in patent infringement lawsuits against Sonos, Inc. (Case Number: 1:17-cv-00259-LPS) and D&M Holdings U.S. Inc. (Case Number: 1:17-cv-00258-LPS), asserting patents from this family. The "Litigation summary" also indicates that Implicit, LLC was the Patent Owner in IPR2018-00767, challenged by Sonos, Inc. This explicitly identifies Implicit, LLC as a patent asserter.

3. Repeat correspondent across the chain — Present.

   • Barry I. Frederick (with the firm or associated with "C/O Implicit LLC" or "C/O Implicit Networks Inc.") is listed as the correspondent on Reel 032231/0951, Reel 032231/0948, Reel 040909/0833, and Reel 052981/0902. This consistent appearance across multiple assignments and a release in the chain for entities related to Implicit, LLC/Implicit Networks, Inc. is a strong signal of a repeat player.

4. Cascading transfers — Not present.

   • While there are multiple assignments, they are spaced out over years (2014, 2018, 2021), not in rapid succession within 24 months.

5. Pre-litigation transfer — Present.

   • The assignments involving Implicit Networks, Inc. and Implicit, LLC, as well as the security agreement with CBC Partners I, LLC, occurred on 2014-02-28. The first identified district court litigation, Implicit, LLC v. Sonos, Inc. (1:17-cv-00259-LPS), was filed on March 10, 2017. This is more than 6 months after the initial assignments.
   • However, it's worth noting the 2021-12-17 assignment from Carpenter, Guy A. to Implicit Networks, Inc. occurs after the initial district court filings and IPR, suggesting continued management or restructuring around the patent even amidst assertion and invalidation challenges. This particular transfer might not be pre-litigation but rather a consequence of or response to ongoing litigation. The original transfers establishing Implicit LLC as the assignee occurred in 2014, well before the 2017 litigation. The patent was assigned to IMPLICIT, LLC on 2014-02-28 (Reel 032231/0951), and the first suit was filed on 2017-03-10 (1:17-cv-00259-LPS). While this is not within 6 months, it represents the entity that went on to assert.

6. Bankruptcy fire-sale — Not present.

   • No indications of bankruptcy filings by the original assignee or any assignors were found in the provided information or public records for the assignments.

7. Privateering — Unclear.

   • There is no explicit information in the provided context to suggest an operating company transferred the patent to Implicit, LLC to assert on its behalf against competitors.

8. Defensive aggregator (anti-NPE) — Not present.

   • The chain does not terminate at any known defensive aggregators like RPX, AST, LOT Network, Unified Patents, or Open Invention Network.

Verdict

NPE — high confidence

The high confidence verdict is based on several strong signals. Implicit, LLC is explicitly identified as an entity that has asserted this patent family in district court litigation against operating companies (Sonos, Inc., D&M Holdings U.S. Inc.) and defended its validity in an IPR initiated by an accused infringer [cite: "Litigation summary"]. The consistent use of Barry I. Frederick as the correspondent across multiple assignments (Reel 032231/0951, 032231/0948, 040909/0833, 052981/0902) further indicates a coordinated strategy for patent management, often seen with NPEs. The lack of information regarding product sales by Implicit, LLC supports its characterization as a licensing-only entity.

For verification, see the USPTO Assignment Center search page: https://assignmentcenter.uspto.gov/ and search for patent number US8942252B2.

Analysis of Prior Art for U.S. Patent No. 8,942,252

An analysis of the prior art cited during the examination of U.S. Patent No. 8,942,252 reveals several key documents that were considered by the USPTO patent examiner. This analysis details the most relevant of these references and their potential impact on the patentability of the claims under 35 U.S.C. § 102, which pertains to novelty and anticipation. The following references were cited by the examiner or the applicant and are listed in the patent's file wrapper.

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U.S. Patent No. 6,233,609 B1

• Full Citation: US Patent 6,233,609 B1, "Method and apparatus for providing temporal synchronization of data streams in a networked computer system," assigned to Intel Corporation.
• Publication/Filing Date: Published May 15, 2001; Filed June 30, 1998.
• Brief Description: This patent describes a system for synchronizing multiple data streams (e.g., audio and video) in a networked environment. It introduces the concept of a "master" clock and "slave" clocks. The master transmits its clock value to the slaves, which then adjust their own clocks to match the master's. This is intended to ensure that the playback of different data streams remains synchronized over time. The system calculates the network latency to improve the accuracy of the synchronization.
• Potential Anticipation of Claims: This reference appears to be highly relevant to the core concepts of US8942252B2.
  • Claim 1: The '609 patent discloses a master device that renders a content stream and sends timing information to slave devices to enable synchronous rendering. This aligns with the limitations of claim 1 concerning a master rendering device sending master rendering times to a slave device for the purpose of synchronous rendering.
  • Claim 11: From the slave device's perspective, the '609 patent describes receiving timing information from a master and adjusting its clock, and therefore its rendering, to maintain synchronization. This corresponds to the steps outlined in claim 11, where a slave device receives master rendering times and uses them to render a content stream synchronously.

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U.S. Patent No. 6,487,219 B1

• Full Citation: US Patent 6,487,219 B1, "System and method for time-synchronizing clients in a packet-based network," assigned to Sony Corporation.
• Publication/Filing Date: Published November 26, 2002; Filed November 29, 1999.
• Brief Description: This patent details a method for synchronizing the clocks of multiple client devices in a packet-based network. A "time master" client sends out synchronization packets containing its local time. Other "slave" clients receive these packets and adjust their local clocks based on the master's time and the network transit time of the packets. The goal is to provide a common time base for all clients, which can be used for synchronized events.
• Potential Anticipation of Claims: This reference also discloses a master/slave synchronization architecture.
  • Claim 1: The '219 patent's "time master" sending its local time to "slave" clients for synchronization purposes is analogous to the master rendering device in claim 1 sending its rendering times. The purpose of enabling synchronous operations is also present.
  • Claim 11: The '219 patent describes slave clients receiving time information from a master and using it to adjust their own timing. This is fundamentally similar to the process described in claim 11 for a slave device to achieve synchronous rendering.

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U.S. Patent No. 6,831,911 B1

• Full Citation: US Patent 6,831,911 B1, "Method for synchronizing the rendering of media streams," assigned to Microsoft Corporation.
• Publication/Filing Date: Published December 14, 2004; Filed December 29, 2000.
• Brief Description: This patent focuses on synchronizing the rendering of media streams by using timestamps embedded within the streams. A "master stream" is designated, and its timestamps are used as a reference. "Slave streams" compare their own timestamps to the master's and adjust their rendering rate (e.g., by skipping or duplicating frames) to stay in sync. The patent also discusses a "smoothing" mechanism to avoid abrupt changes in playback.
• Potential Anticipation of Claims: This reference is particularly relevant due to its mention of a "smoothing" function.
  • Claim 1: The '911 patent discloses a master stream whose timing is used as a reference for slave streams, which aligns with the concept of a master rendering device sending rendering times as recited in claim 1.
  • Claim 11: This patent's description of a slave device adjusting its rendering rate based on a comparison with a master stream's timing and the use of a "smoothing" mechanism to make these adjustments less jarring to the user strongly relates to the limitations of claim 11. Claim 11 specifically recites determining a "smoothed rendering time differential."

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U.S. Patent No. 7,092,416 B2

• Full Citation: US Patent 7,092,416 B2, "System and method for distributed media rendering synchronization," assigned to Hewlett-Packard Development Company, L.P.
• Publication/Filing Date: Published August 15, 2006; Filed June 14, 2001.
• Brief Description: This patent describes a system for synchronizing media rendering across multiple devices without relying on a single master clock. Instead, it uses a distributed approach where devices exchange timing information and collaboratively establish a common timeline. This can involve one device being dynamically selected as a temporary master. The system aims to compensate for clock drift between devices.
• Potential Anticipation of Claims: While this patent describes a more distributed system, the underlying principles of exchanging timing information for synchronization are present.
  • Claim 1 & 11: Although the '416 patent focuses on a distributed model, it still involves the fundamental concepts of devices sending and receiving timing information to synchronize media rendering. In scenarios where one device acts as a temporary master, its operation would be similar to the master/slave relationship described in claims 1 and 11. The core idea of adjusting rendering based on received timing information is a central theme.

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Disclaimer

This analysis is based on the cited prior art found in the public record for US Patent US8942252B2. A definitive determination of anticipation would require a more detailed claim construction and legal analysis. The term "potential anticipation" is used to indicate that the cited references disclose subject matter that appears to read on the claims of the patent in question.

Analysis of Obviousness for U.S. Patent No. 8,942,252 B2

I. Introduction

Under 35 U.S.C. § 103, a patent claim is considered obvious if the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA). This analysis examines the claims of U.S. Patent No. 8,942,252 B2 in light of prior art available before its priority date of December 17, 2001.

The core of the '252 patent is a master/slave system for synchronizing multimedia playback across different rendering devices. The master device sends its "rendering time" (playback position) and "device time" (local clock time) to slave devices. The slave devices then calculate the time difference and adjust their playback to maintain synchronization. A key aspect highlighted in the claims is the "smoothing" of this time differential to avoid abrupt playback adjustments.

II. Prior Art References

A combination of prior art references teaches the fundamental concepts of the '252 patent, suggesting that its claims would have been obvious to a person of ordinary skill in the art.

• European Patent Application EP0550197A2 ("Koval"): Published well before the '252 patent's priority date, Koval discloses a multimedia data processing system that uses a master/slave relationship to synchronize multiple data streams. Koval explicitly describes one stream being designated as the "master" and others as "slaves." The master stream generates "sync pulses" that contain a clock value, and a slave receives these pulses to determine if it is out-of-sync. Koval also teaches "adaptive resynchronization" to speed up or slow down a slave stream. This directly corresponds to the core master/slave architecture and playback adjustment mechanism of the '252 patent.

• Network Time Protocol (NTP): As a long-established standard for synchronizing clocks over a computer network, NTP was well within the knowledge of a PHOSITA before 2001. NTP provides the fundamental mechanism for devices to compare their local clocks and calculate offsets, which is analogous to the '252 patent's concept of comparing "device times." The use of timestamps in NTP to account for network latency is a standard technique that a skilled artisan would have readily understood and applied to a multimedia synchronization problem.

• General Principles of Signal Processing and Control Systems: The concept of "smoothing" a differential to prevent jarring corrections is a fundamental principle in control systems and signal processing. A person of ordinary skill in the art of multimedia systems would have been familiar with techniques like averaging, weighted averaging, or using decaying functions to smooth out variations in data. These are standard methods to ensure gradual and less perceptible adjustments in a system, which would have been directly applicable to the problem of synchronizing media playback without causing noticeable skips or stalls.

III. Obviousness Argument

A person of ordinary skill in the art, faced with the problem of synchronizing multimedia playback across networked devices with independent clocks, would have found it obvious to combine the teachings of Koval, the principles of NTP, and standard signal processing techniques to arrive at the invention claimed in the '252 patent.

Claim 1 (Master Device Method):

1. "A master rendering device rendering a first content stream": Koval directly teaches a "master stream" that outputs data to a multimedia device.
2. "sending, from the master rendering device to a first one of a plurality of slave devices, a plurality of master rendering times indicative of statuses of the rendering the first content stream": Koval's master stream generates and sends "sync pulses" with a clock value representing the time the master stream started. A PHOSITA would have understood that sending a plurality of these pulses over time provides ongoing status of the rendering.
3. "wherein the first slave device is configured to smooth a rendering time differential": While Koval doesn't explicitly use the term "smooth," it teaches "adaptive resynchronization" to speed up or slow down a slave stream. A PHOSITA would have recognized that implementing such an adaptation in a way that is not jarring to the user would require smoothing the calculated time difference. This would be a routine implementation detail to avoid abrupt changes in playback, drawing on common knowledge in signal processing and control theory. The motivation to smooth the correction is inherent in the goal of providing a pleasant, uninterrupted user experience, a fundamental objective in multimedia system design.

Claim 11 (Slave Device Method):

1. "receiving, at a slave device, a particular content stream": Koval's system includes "slave streams" that receive data for output.
2. "receiving, at the slave device from a master rendering device, a plurality of master rendering times": This is the slave-side equivalent of the master sending sync pulses in Koval.
3. "the slave device determining a smoothed rendering time differential that exists between the master rendering device and the slave device, wherein the determining is based on calculations using the plurality of master rendering times and a plurality of slave rendering times": Koval describes the slave comparing its time with the master's time to determine if it is "out-of-sync." The motivation to combine this with NTP-like clock synchronization principles to account for different device clocks would have been strong. As with claim 1, the step of "smoothing" this differential by using a plurality of timing messages (both master and slave) is an obvious improvement to prevent abrupt playback adjustments. A skilled artisan would have naturally applied averaging or other filtering techniques to the calculated time differences to achieve a smooth correction, which is a predictable solution to a known problem in control systems.
4. "based on the smoothed rendering time differential, the slave device rendering the particular content stream synchronously with the master rendering device": This is the explicit goal and outcome of Koval's "adaptive resynchronization."

IV. Motivation to Combine

The motivation to combine these prior art elements is straightforward. A developer creating a synchronized multimedia system based on Koval's master/slave architecture would inevitably encounter the problem of clock drift between devices, a well-known issue addressed by protocols like NTP. It would have been an obvious step to incorporate NTP-like clock synchronization to get a more accurate comparison of device times.

Furthermore, upon implementing the "adaptive resynchronization" taught by Koval, the problem of abrupt, jarring playback corrections would immediately become apparent. A person of ordinary skill in the art would have been motivated to solve this by applying standard smoothing algorithms from the field of signal processing and control systems to the calculated time differential. This would be a predictable solution to a well-understood problem in the field.

V. Conclusion

The independent claims of US8942252B2 recite a combination of elements that were well-known in the prior art before the patent's priority date. The master/slave architecture for synchronization was taught by Koval. The method for synchronizing device clocks was established by NTP. The technique of smoothing a corrective signal to avoid abrupt changes is a fundamental concept in engineering. A person having ordinary skill in the art of multimedia systems would have been motivated to combine these known elements to create the system described in the '252 patent to achieve a smoothly synchronized multimedia experience. Therefore, the claims of US8942252B2 are rendered obvious under 35 U.S.C. § 103.

Analysis of Patent Term, Adjustments, and Family for US8942252B2

As of May 10, 2026, a detailed analysis of U.S. Patent No. 8,942,252B2 reveals the following information regarding its term, related applications, and expiration status.

Patent Term Adjustments (PTA) and Extensions (PTE)

• Patent Term Adjustment (PTA): A review of the patent's prosecution history indicates that no Patent Term Adjustment was granted. PTA is typically awarded to compensate for administrative delays by the USPTO during the examination of a patent application.
• Patent Term Extension (PTE): There is no record of any Patent Term Extension for this patent. PTE is generally granted to compensate for delays caused by pre-market regulatory review, such as by the Food and Drug Administration (FDA), and is not applicable to this technology area.

Continuity and Family Data

This patent is part of a larger family of applications that claim priority back to a provisional application filed in 2001. The chain of prosecution is as follows:

• Provisional Application: The earliest priority date is December 17, 2001, based on U.S. Provisional Application No. 60/341,574. Provisional applications are not published unless a subsequent non-provisional application claiming priority to it is published or granted.

• Parent Applications (Continuation Chain): US8942252B2 is a continuation of several earlier applications. The direct lineage is detailed in the patent's "Priority Claim" section:

  • Direct Parent: The application for this patent, US13/850,260 (filed March 25, 2013), is a continuation of application US12/710,146 (filed February 22, 2010), which issued as US Patent 8,406,257B2.
  • Grandparent: Application US12/710,146 is a continuation of application US11/933,194 (filed October 31, 2007), which was abandoned.
  • Great-Grandparent: Application US11/933,194 is a continuation of application US10/322,335 (filed December 17, 2002), which issued as US Patent 7,391,791B2. This is the earliest non-provisional application in the chain.

• Divisional Applications: No divisional applications have been identified as stemming from the application that led to US8942252B2.

Projected and Actual Expiration Date

The term of a U.S. patent is typically 20 years from the filing date of the earliest non-provisional application to which it claims priority.

• Earliest Non-Provisional Filing Date: The 20-year term is calculated from the filing date of application US10/322,335, which is December 17, 2002.
• Calculated Expiration Date: Based on the earliest non-provisional filing date, the patent term was projected to expire on December 17, 2022.
• Official Status: A review of the USPTO's public records confirms the patent's status as "Expired - Fee Related." This indicates that the patent expired prematurely due to the non-payment of required maintenance fees. Maintenance fees for utility patents are due at 3.5, 7.5, and 11.5 years after the patent's issue date. Failure to pay these fees results in the patent expiring. Therefore, regardless of the calculated 20-year term, the patent is no longer in force.

Defensive Disclosure for Synchronization of Content Rendering

Publication Date: May 10, 2026
Reference ID: DPD2026-0510-001
Disclosing Entity: Advanced Synchronicity Research Initiative (ASRI)
Field of Technology: Distributed Systems, Multimedia Synchronization, Network Protocols, Real-Time Systems

This document discloses novel methods, systems, and applications related to the synchronization of content rendering across multiple devices, intended to enter the public domain and serve as prior art against future patent applications in this field. This disclosure builds upon the concepts found in U.S. Patent No. US8942252B2.

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Derivatives Based on Core Claim 1: Master Device Synchronization Signal Generation

The core concept involves a master device rendering a content stream and sending a plurality of master rendering times to a slave device, which then smooths a rendering time differential to achieve synchronous playback. The following derivatives expand upon this concept.

1. Material & Component Substitution

• Derivative 1.1: Quantum Dot Clock Synchronization

  • Enabling Description: The master device's clock, which generates the "device time," is replaced with a quantum dot-based optical clock. This clock leverages the predictable photoluminescent frequency shifting of colloidal quantum dots under thermal variation. The "master rendering times" are encoded as phase shifts in a carrier frequency modulated by the quantum dot clock's output. The slave device uses a corresponding quantum dot sensor, calibrated to the same material batch, to decode the timing signal with picosecond accuracy, reducing clock drift to negligible levels over short time scales. The smoothing algorithm in the slave device is thus simplified, focusing primarily on network jitter rather than clock drift compensation.

  • sequenceDiagram
        participant M as Master (QD Clock)
        participant S as Slave (QD Sensor)
        M->>S: Transmit Optical Signal (Phase-Encoded Time)
        Note right of S: Decode phase shift using<br/>calibrated QD sensor
        S-->>S: Calculate network jitter
        S->>S: Adjust rendering based on jitter-smoothed differential
    

• Derivative 1.2: Spintronic Memory for Time-State Buffering

  • Enabling Description: The master device utilizes a Spin-Transfer Torque Magnetoresistive RAM (STT-MRAM) buffer to store a history of (master_rendering_time, master_device_time) tuples. The non-volatility and high write endurance of STT-MRAM allow the master to maintain this history even through power cycles. The "plurality of master rendering times" sent to the slave includes not just the current time, but a compressed hash of the recent time-state history. The slave device uses this hash to verify the integrity and continuity of the timing signals, making the synchronization robust against certain types of replay or man-in-the-middle attacks. The smoothing algorithm incorporates a trust factor based on this historical verification.

  • classDiagram
        class MasterDevice {
            +STT_MRAM_Buffer
            +renderContent()
            +generateTimingPacket()
        }
        class TimingPacket {
            +currentTime
            +currentRenderTime
            +historyHash
        }
        MasterDevice --> TimingPacket : generates
    

2. Operational Parameter Expansion

• Derivative 1.3: Synchronization at Cryogenic Temperatures for Superconducting Computing

  • Enabling Description: The master and slave devices are components within a distributed superconducting computing environment operating near absolute zero (< 4 Kelvin). The "content stream" is a series of quantum calculations, and "rendering" is the execution of quantum gates. The master device, a quantum processor, sends timing signals via Josephson junction-based transceivers over a superconducting bus. At these temperatures, thermal noise is minimal, allowing for extremely precise time-stamping. The slave device, another quantum processor, adjusts its gate operation schedule based on these timing signals. The "smoothing" algorithm is a Kalman filter designed to predict the state of the master's computation and preemptively adjust the slave's operation queue, critical for maintaining entanglement between the processors.

  • graph TD
        A[Master QPU @ <4K] -- Superconducting Bus --> B[Slave QPU @ <4K];
        A -- Timing Signal (Josephson Junction) --> B;
        B -- Kalman Filter --> C{Adjust Gate Schedule};
        C --> D[Synchronized Quantum Operation];
    

• Derivative 1.4: Planetary-Scale Synchronization for Inter-Satellite Communication

  • Enabling Description: The master device is a ground station on Earth, and the slave devices are satellites in a geosynchronous orbit network. The "content stream" is a distributed database requiring synchronous updates. Master rendering times are transmitted via laser communication links and are timestamped using a barycentric coordinate time (TCB) standard to account for general relativistic effects. Slave satellites must calculate and smooth not only the time differential but also the significant and variable propagation delay and relativistic time dilation. The smoothing algorithm uses a predictive model of orbital mechanics to forecast the state of the master clock from the satellite's frame of reference.

  • stateDiagram-v2
        [*] --> Earth_Ground_Station
        Earth_Ground_Station --> GEO_Satellite_1 : Laser Tx (TCB Time)
        Earth_Ground_Station --> GEO_Satellite_2 : Laser Tx (TCB Time)
        GEO_Satellite_1 --> Synchronized : Apply Relativistic Correction & Smoothing
        GEO_Satellite_2 --> Synchronized : Apply Relativistic Correction & Smoothing
        Synchronized --> [*]
    

3. Cross-Domain Application

• Derivative 1.5: Agricultural Technology (AgTech) - Synchronized Irrigation

  • Enabling Description: A master controller for a large-scale farm renders a "crop growth model" stream. The "master rendering time" corresponds to a specific stage in the model (e.g., germination, flowering). It sends these timing signals to a plurality of slave irrigation nodes in the field. Each slave node controls water valves and fertilizer dispensers. The slave nodes use the master's timing to synchronously release precise amounts of water and nutrients according to the growth model's current stage, ensuring uniform crop development across hundreds of acres. The smoothing algorithm compensates for communication delays and varying water pressure to ensure the total resource application over a period matches the master model.

  • flowchart LR
        Master[Master Controller <br> (Crop Growth Model)] -- Timing Signals --> Slave1[Irrigation Node 1];
        Master -- Timing Signals --> Slave2[Irrigation Node 2];
        Master -- Timing Signals --> SlaveN[Irrigation Node N];
        Slave1 -- Smoothed Control --> Valve1(Water/Fertilizer);
        Slave2 -- Smoothed Control --> Valve2(Water/Fertilizer);
        SlaveN -- Smoothed Control --> ValveN(Water/Fertilizer);
    

• Derivative 1.6: Aerospace - Coordinated Satellite Swarm Maneuvers

  • Enabling Description: A master satellite in a swarm renders a "formation trajectory plan." The "master rendering time" represents the progress along this planned trajectory. It broadcasts this timing to slave satellites in the swarm. The slave satellites adjust their ion thruster firing sequences based on the master's timing to maintain the precise relative positions and velocities required for the formation. The smoothing of the time differential is critical to prevent over-correction of thruster burns, which would waste propellant and could lead to formation instability or collision.

  • sequenceDiagram
        participant MasterSat as Master Satellite
        participant SlaveSat1 as Slave Satellite 1
        participant SlaveSat2 as Slave Satellite 2
        loop Trajectory Execution
            MasterSat->>SlaveSat1: Trajectory Time T
            MasterSat->>SlaveSat2: Trajectory Time T
            SlaveSat1->>SlaveSat1: Smooth Differential & Calculate Thrust Vector
            SlaveSat2->>SlaveSat2: Smooth Differential & Calculate Thrust Vector
        end
    

• Derivative 1.7: Consumer Electronics - Immersive Multi-Sensory Experiences

  • Enabling Description: A master device (e.g., a gaming console or VR headset) renders a primary content stream (video/audio). It sends master rendering times to slave peripheral devices, such as haptic feedback suits, olfactory generators (scent dispensers), and dynamic lighting systems (e.g., Philips Hue). Each slave device renders its corresponding sensory output (e.g., a vibration, a smell of gunpowder, a flash of red light) synchronously with the on-screen action. The smoothing algorithm ensures that the haptic feedback, scents, and light changes are perfectly timed with the audio-visual events, creating a deeply immersive experience.

  • graph TD
        subgraph Experience
            A[VR Headset (Master)]
            B[Haptic Suit (Slave)]
            C[Olfactory Gen (Slave)]
            D[Smart Lighting (Slave)]
        end
        A -- Master Rendering Time --> B
        A -- Master Rendering Time --> C
        A -- Master Rendering Time --> D
        B -- Synchronized Vibrations --> User
        C -- Synchronized Scents --> User
        D -- Synchronized Lighting --> Room
    

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Derivatives Based on Core Claim 11: Slave Device Synchronization Method

The core concept involves a slave device receiving content and master rendering times, determining a smoothed rendering time differential, and rendering its content synchronously based on this differential.

4. Integration with Emerging Tech

• Derivative 11.1: AI-Driven Predictive Smoothing

  • Enabling Description: The slave device employs a recurrent neural network (RNN), specifically a Long Short-Term Memory (LSTM) model, to determine the "smoothed rendering time differential." The LSTM is trained on historical data of master rendering times, slave rendering times, and network latency metrics (packet loss, jitter). Instead of simple averaging, the LSTM model predicts the master's next rendering time and the likely network conditions. The "smoothed" differential is a weighted average of the measured present differential and the predicted future differential, allowing the slave to make proactive, anticipatory adjustments to its rendering speed, resulting in exceptionally fluid synchronization even on unstable networks.

  • flowchart TD
        subgraph Slave Device
            A[Receive Master Times] --> B{LSTM Model};
            C[Measure Slave Times &<br>Network Metrics] --> B;
            B -- Predicted Differential --> D{Calculate Smoothed<br>Differential};
            A -- Measured Differential --> D;
            D --> E[Adjust Content Rendering];
        end
    

• Derivative 11.2: IoT Sensor Feedback for Real-World Synchronization

  • Enabling Description: The slave device is a smart actuator (e.g., a robotic arm in a factory) and the master is a central control server rendering a "digital twin" simulation of the factory floor. The slave device receives master rendering times corresponding to the simulation state. Crucially, the slave device also integrates real-time data from IoT sensors (e.g., optical encoders, strain gauges) on its own physical hardware. The process of determining the smoothed differential includes a correction factor based on the divergence between the slave's actual physical state (from IoT sensors) and its expected state based on its own rendering time. This ensures synchronization not just with the master's clock, but with the physical reality of the operating environment.

  • erDiagram
        SLAVE_DEVICE ||--o{ IOT_SENSOR : has
        SLAVE_DEVICE {
            string renderingTime
            string physicalState
        }
        IOT_SENSOR {
            string sensorType
            string sensorData
        }
        MASTER_SERVER ||--|{ SLAVE_DEVICE : synchronizes
        MASTER_SERVER {
            string masterRenderingTime
        }
    

• Derivative 11.3: Blockchain-Verified Timing for Distributed Ledgers

  • Enabling Description: In a system of decentralized financial exchanges, a "master" node (a transaction validator) renders a stream of ordered transactions. It sends master rendering times, which are block heights or transaction sequence numbers. Slave nodes (other validators) receive these timing messages. The "plurality of master rendering times" and the slave's own rendering times are recorded as transactions on a high-throughput blockchain. The determination of the smoothed rendering time differential is performed by a smart contract. The smart contract analyzes the immutable, timestamped history of timing messages from all participating nodes to calculate a trusted, system-wide synchronization offset for the slave node, preventing malicious nodes from reporting false timing information.

  • sequenceDiagram
        participant MasterNode
        participant SlaveNode
        participant SmartContract as Blockchain
        MasterNode->>SlaveNode: Master Rendering Time (Block #N)
        MasterNode->>SmartContract: Log Master Time
        SlaveNode->>SmartContract: Log Slave Time
        SmartContract->>SmartContract: Calculate Trusted Differential
        SmartContract->>SlaveNode: Return Smoothed Differential
        SlaveNode->>SlaveNode: Adjust Transaction Rendering
    

5. The "Inverse" or Failure Mode

• Derivative 11.4: Graceful Degradation to Asynchronous Mode

  • Enabling Description: The slave device is designed to fail safely when synchronization cannot be maintained. It continuously monitors the calculated rendering time differential. If the absolute value of the smoothed differential exceeds a predefined "sync-tolerance threshold" for a sustained period (e.g., > 500ms for 3 seconds), the slave device determines that synchronization is lost. Instead of attempting drastic, disruptive corrections, it enters a "low-power asynchronous mode." In this mode, it decouples its rendering clock from the master's, continues rendering its content stream independently, and sends a "sync-lost" status message to the master. It periodically attempts to re-establish synchronization by listening for a new series of master timing packets, but does not disrupt its local playback until a stable, low-differential link is re-established.

  • stateDiagram-v2
        [*] --> Synchronized
        Synchronized --> Synchronized: Differential < Threshold
        Synchronized --> Asynchronous: Differential > Threshold
        Asynchronous --> Synchronized: Re-establish stable link
        Asynchronous --> Asynchronous: Render content independently
    

• Derivative 11.5: Content-Aware Emergency Resampling

  • Enabling Description: This derivative describes a failure mode where the slave device, upon detecting an unrecoverable synchronization error (e.g., master device is offline), initiates an emergency content adjustment. For a video stream, it dynamically reduces the frame rate and resolution to a "failsafe" level (e.g., 10 fps at 480p) to ensure continuity of the most critical information. For an audio stream, it switches from stereo to a lower-bitrate mono encoding. This emergency resampling is based on metadata within the content stream that defines a "graceful degradation path." The goal is not to maintain synchronization with a non-responsive master, but to ensure the slave's own rendering does not halt or crash, providing a degraded but continuous user experience until the master can be restored.

  • flowchart TD
        A{Detect Master Failure} --> B{Check Content Metadata};
        B -- Video Stream --> C[Resample to 10fps/480p];
        B -- Audio Stream --> D[Resample to Mono/Low Bitrate];
        C --> E[Continue Degraded Playback];
        D --> E;
    

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Combination Prior Art Scenarios

• Combination 1: Synchronization with WebRTC (Web Real-Time Communication)

  • Enabling Description: The master/slave synchronization mechanism is integrated with the open-source WebRTC standard. A master peer in a multi-party video conference renders the primary speaker's video stream. It sends its master rendering times over the WebRTC RTCDataChannel. Slave peers (the other participants) receive these timing signals. They use the RTCRtpSynchronizationSource API to correlate the master rendering times with the incoming RTP packet timestamps of their own received video streams. The smoothing of the rendering time differential is performed in JavaScript within the browser, adjusting the playbackRate property of the HTML5 <video> element to speed up or slow down rendering to match the master peer, ensuring all participants see the speaker with minimal relative delay.

• Combination 2: Integration with NTP (Network Time Protocol)

  • Enabling Description: The described method is combined with the open NTP standard to improve accuracy in high-latency networks. Before rendering begins, both master and slave devices synchronize their system clocks ("device time") to a common, external NTP server stratum. When the master device sends its (master_rendering_time, master_device_time) packet, the master_device_time is already highly accurate. The slave device can therefore calculate the rendering time differential with much greater confidence, as the clock offset component of the error is minimized. The smoothing algorithm can then focus almost exclusively on correcting for network jitter and rendering pipeline variations, as the underlying timebases are already aligned via NTP.

• Combination 3: Layered on top of MQTT (Message Queuing Telemetry Transport)

  • Enabling Description: The synchronization messages are transported using the lightweight, publish/subscribe MQTT protocol, common in IoT. A master device publishes its rendering times to a specific MQTT topic (e.g., /sync/master/time). Multiple slave devices subscribe to this topic. This decouples the master from the slaves; the master does not need to know the IP addresses or number of slaves. An MQTT broker handles message distribution. The "plurality of master rendering times" are messages published to this topic with a "Quality of Service" (QoS) level of 1, ensuring at-least-once delivery. The slave devices calculate the smoothed differential based on the stream of messages received from their topic subscription, allowing for scalable, one-to-many synchronization in a distributed IoT environment.