Sonos Inc v. Implicit LLC

1. Case Identification

• Patent #: 8,942,252
• Filed: March 9, 2018
• Petitioner(s): Sonos, Inc.
• Patent Owner(s): Implicit, LLC
• Challenged Claims: 1-3, 8, 11, and 17

2. Patent Overview

• Title: Synchronizing Rendering of Content Across Multiple Devices
• Brief Description: The ’252 patent describes methods for synchronizing the rendering of content across multiple networked devices (e.g., for audio, video, and text) that may have different internal clocks or "time domains." The technology uses a master-slave architecture where slave devices synchronize their playback to a master device by calculating and compensating for differentials in both device time (clock time) and rendering time (content playback progress).

3. Grounds for Unpatentability

Ground 1: Claims 1-3, 8, 11, and 17 are obvious over Janevski, alone or in view of Azevedo.

• Prior Art Relied Upon: Janevski (Patent 7,269,338) and Azevedo (a 1995 publication on fault-tolerant clock synchronization).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Janevski discloses a system that mirrors the core invention of the ’252 patent. Janevski teaches a master-slave system ("initiator" and "participant" Personal Video Recorders) for synchronized media playback. The system periodically calculates two types of differentials: a "time misregistration" (a clock differential, analogous to the ’252 patent’s device time differential) and a "frame misregistration" (a content playback differential, analogous to the rendering time differential). Petitioner asserted this maps to all limitations of the independent claims except for the explicit step of "smoothing" these calculated differentials.
  • Motivation to Combine: Petitioner contended that adding a "smoothing" function to Janevski's periodically calculated differentials would be a predictable and trivial modification for a person of ordinary skill in the art (POSITA). Given Janevski’s stated goal of achieving "precise synchronization," a POSITA would be motivated to apply well-known smoothing techniques (like averaging) to reduce volatility and improve the accuracy of the periodic differential calculations. Petitioner highlighted that Janevski itself cites the Azevedo paper as an example of a known time synchronization technique, and Azevedo explicitly discloses smoothing a "clock correction term" using a weighted average to "attenuate" volatility.
  • Expectation of Success: Applying a standard mathematical technique like smoothing to a stream of data values was a well-understood practice with predictable results, ensuring a high expectation of success.

Ground 2: Claims 1-3, 8, 11, and 17 are obvious over Janevski in view of Baumgartner.

• Prior Art Relied Upon: Janevski (Patent 7,269,338) and Baumgartner (Patent 5,642,171).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground focused on smoothing the content-based differential. Petitioner argued that Janevski teaches the periodic calculation of a "frame" (content) differential. Baumgartner, in turn, discloses a method for synchronizing separate audio and video data streams by computing a "synchronization error value" (a frame differential) and then applying a "smoothing function" (a weighted average of prior tempo values) to adjust the video rendering and prevent overcompensation.
  • Motivation to Combine: Petitioner asserted that a POSITA would be motivated to combine these teachings because both references share the common objective of precise, stable multimedia synchronization. A POSITA would have logically applied Baumgartner's technique of smoothing a frame-based differential to Janevski's system to achieve the same explicitly stated benefits: preventing overcompensation and enabling smoother, more stable synchronized playback.
  • Expectation of Success: The combination involved applying a known technique (smoothing) for its intended purpose (improving stability) in a very similar technical context, leading to a high expectation of success.

• Additional Grounds: Petitioner asserted additional obviousness challenges against claims 1-3, 8, 11, and 17, combining Janevski with Mills (a 1992 publication on Network Time Protocol), Berthaud (a 2000 publication on time synchronization), or Eidson (Patent 6,278,710). Petitioner argued that Janevski’s disclosure that its time synchronization mechanism could be implemented in "many different known ways" provided a direct motivation to combine it with these references. Each of these secondary references was asserted to explicitly teach applying smoothing functions (e.g., averaging, filtering, deglitching) to clock offset calculations in networked systems, providing alternative and reinforcing reasons why a POSITA would have found it obvious to add the claimed "smoothing" function to Janevski's system.

4. Key Claim Construction Positions

• "device time" and "rendering time": Petitioner proposed constructions consistent with the patent’s explicit definitions: "device time" as clock time and "rendering time" as a measure of content progress.
• "sending/receiving a plurality of master rendering times": Petitioner argued that this term, in light of the Patent Owner's positions in parallel litigation, should be construed broadly to cover not only measures of rendered content but also general "timestamps related to playback."
• "smooth a rendering time differential" / "determining a smoothed rendering time differential": This was the most critical construction for Petitioner's case. Petitioner argued for a broad construction wherein "smoothing" is applied to a differential of either device time (clock time) or rendering time. Petitioner asserted this construction was necessary to encompass the Patent Owner's litigation theories and was central to its obviousness arguments, which heavily relied on prior art teaching the smoothing of clock time differentials in networked systems.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-3, 8, 11, and 17 of Patent 8,942,252 as unpatentable.