Apple Inc v. Saint Lawrence Communications LLC

1. Case Identification

• Case #: IPR2017-01244
• Patent #: 6,807,524
• Filed: April 4, 2017
• Petitioner(s): Apple Inc.
• Patent Owner(s): Saint Lawrence Communications LLC
• Challenged Claims: 1-21 and 29-42

2. Patent Overview

• Title: Perceptual Weighting of Speech Signals
• Brief Description: The ’524 patent describes a speech encoding system using Code Excited Linear Prediction (CELP) for wideband speech signals. The purported invention is a modified perceptual weighting filter with a fixed denominator, which allegedly decouples the weighting of the signal in a formant region from the spectral tilt of the signal.

3. Grounds for Unpatentability

Ground 1: Claims 1, 8, 15, 29, and 36 are obvious over Salami in view of Kroon.

• Prior Art Relied Upon: Salami ("Real-time Implementation of a 9.6 kbit/s ACELP Wideband Speech Coder," Dec. 1992) and Kroon ("Regular-Pulse Excitation—A Novel Approach to Effective and Efficient Multipulse Coding of Speech," Oct. 1986).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Salami disclosed a wideband ACELP speech coder that met nearly all limitations of the independent claims, including using a pre-emphasis filter to control spectral tilt and a separate perceptual weighting filter to control formant weighting, thereby decoupling the two functions. However, Salami’s perceptual weighting filter had a denominator that varied in time with the synthesis filter coefficients. Kroon was cited for its teaching of using a "fixed error weighting filter" with a "time-invariant" impulse response to reduce the computational complexity of the coder.
  • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would combine the teachings of Salami and Kroon because both references address the same problem of optimizing LP speech coders while minimizing computational requirements. A POSITA seeking to improve the computational efficiency of Salami's coder would have looked to contemporary art like Kroon, which explicitly taught that a fixed denominator provides a comparable quality with the advantage of "ease of implementation."
  • Expectation of Success: The substitution of Kroon's fixed denominator for Salami's dynamic one was presented as a simple design choice with predictable results, namely reduced computational load without sacrificing significant speech quality.

Ground 2: Claims 2-3, 9-10, 16-17, 30-31, and 37-38 are obvious over Salami in view of Kroon and Makamura.

• Prior Art Relied Upon: Salami, Kroon, and Makamura (Patent 5,295,224).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground built upon the Salami and Kroon combination to address dependent claims requiring a specific pre-emphasis factor (µ). Petitioner argued that while Salami disclosed the pre-emphasis filter function, it did not specify a value range for µ. Makamura, which also discloses a CELP coder, was cited for explicitly teaching a pre-emphasis filter coefficient having a value located between 0 and 1.
  • Motivation to Combine: A POSITA implementing the Salami/Kroon coder would have been motivated to consult references like Makamura to determine optimal and conventional parameter values. Petitioner asserted that bounding the pre-emphasis factor between 0 and 1 was a standard, known practice for stable filter design, and Makamura confirmed this. Selecting a value of 0.7, as claimed in other dependent claims, was argued to be prima facie obvious as it falls within this known range and was a matter of routine optimization.
  • Expectation of Success: Applying Makamura's standard parameter range to the Salami/Kroon combination would predictably result in a stable and effective pre-emphasis filter, as this was a common technique in the field.

Ground 3: Claims 6, 13, 20, 34, and 41 are obvious over Salami in view of Kroon, Lim, and '524 APA.

• Prior Art Relied Upon: Salami, Kroon, Lim ("Enhancement and Bandwidth Compression of Noisy Speech," Dec. 1979), and the Admitted Prior Art of the '524 patent ('524 APA).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground addressed claims reciting a specific transfer function for the perceptual weighting filter. Petitioner argued that Lim disclosed a general pole-zero transfer function well-suited for modeling speech and its formants. The '524 APA was cited for admitting that the specific boundaries for the weighting control values (γ1 and γ2) were "traditional" and "well known" in the art.
  • Motivation to Combine: A POSITA would combine Lim with the Salami/Kroon framework to improve performance, as Lim’s pole-zero model was known to be more robust for representing the vocal tract. Petitioner argued it would be a matter of routine engineering to apply Lim's superior filter structure to Salami's system and then set the weighting control values within the conventional ranges admitted as known by the '524 patent itself.
  • Expectation of Success: The combination was presented as a predictable integration of known filter design principles, where a more advantageous filter model (Lim) would be used with conventional parameter ranges ('524 APA) to achieve improved, yet expected, performance.

• Additional Grounds: Petitioner asserted an additional obviousness challenge against claims 4-5, 7, 11-12, 14, 18-19, 21, 32-33, 35, 39-40, and 42 based on a combination of Salami, Kroon, Lim, '524 APA, and Makamura. This ground argued that setting a specific weighting factor (γ2) equal to the pre-emphasis factor (µ) would have been an obvious design choice to compensate for the effects of pre-emphasis, a technique explicitly taught by Makamura.

4. Key Claim Construction Positions

• "fixed denominator": Petitioner argued, based on the prosecution history, that this term means the denominator of the perceptual weighting filter's transfer function is fixed with respect to the variable of time. This construction was central to the argument that Kroon's "time-invariant" filter supplied the missing element in Salami.
• Means-Plus-Function Terms: For several terms construed under 35 U.S.C. § 112(6) (e.g., "pitch codebook search device"), Petitioner adopted the constructions from a related district court case. However, Petitioner noted that these constructions were incomplete and that other structures and algorithms disclosed in the '524 patent specification also corresponded to the claimed functions.

5. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-21 and 29-42 of the ’524 patent as unpatentable.