DCT

1:19-cv-07397

EVS Codec Tech LLC v. LG Electronics Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:18-cv-00343, E.D. Tex., 04/10/2019
  • Venue Allegations: Venue is alleged to be proper as to the U.S. defendants because they have regular and established places of business within the Eastern District of Texas and have allegedly committed acts of infringement there. Venue as to the foreign parent corporation is based on general venue statutes for foreign defendants.
  • Core Dispute: Plaintiff alleges that Defendant’s mobile devices, such as smartphones and tablets, that are capable of practicing the Enhanced Voice Services (EVS) Codec standard infringe five U.S. patents related to speech and audio compression technologies.
  • Technical Context: The technology at issue is the EVS Codec, an international standard for delivering high-definition voice services over modern mobile networks like LTE (VoLTE), significantly improving call quality and efficiency.
  • Key Procedural History: The complaint alleges a complex history between the parties, including prior litigation where the same patents were asserted against LG products using the AMR-WB codec, which was dismissed following a license agreement. The complaint further alleges that LG previously asserted counterclaims of invalidity against the patents-in-suit, which were dismissed with prejudice, raising the possibility that LG may be barred from re-litigating validity under the doctrines of res judicata or collateral estoppel. The court is noted as having presided over several other cases involving the patents-in-suit, including issuing two claim construction opinions.

Case Timeline

Date Event
1998-10-27 Earliest Priority Date for ’805, ’524, ’802, and ’521 Patents
1999-11-18 Earliest Priority Date for ’123 Patent
2004-09-21 U.S. Patent No. 6,795,805 Issues
2004-10-19 U.S. Patent No. 6,807,524 Issues
2006-12-19 U.S. Patent No. 7,151,802 Issues
2007-03-13 U.S. Patent No. 7,191,123 Issues
2007-08-21 U.S. Patent No. 7,260,521 Issues
2016-01-01 T-Mobile network launch of EVS Codec (earliest date alleged)
2019-04-10 Third Amended Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,795,805 - "Periodicity Enhancement in Decoding Wideband Signals"

The Invention Explained

  • Problem Addressed: The patent addresses the challenge that prior art methods for enhancing the periodicity of excitation signals in speech codecs, while effective for narrow-band telephone signals, were less efficient for wideband signals because they introduced periodicity across the entire frequency spectrum (U.S. US6795805B1, col. 2:19-29).
  • The Patented Solution: The invention proposes filtering an "innovative codevector" (a component of the excitation signal) to specifically reduce its energy in the low-frequency portion of the signal. This targeted filtering enhances the periodicity of the overall excitation signal primarily at lower frequencies, which is described as more effective for improving the quality of voiced segments in wideband speech (U.S. 6,795,805 B1, Abstract; col. 2:30-42).
  • Technical Importance: This technique offered a more spectrally-targeted and efficient method to improve the perceived quality and naturalness of synthesized wideband speech, a key goal for next-generation digital voice communications (U.S. 6,795,805 B1, col. 2:10-18).

Key Claims at a Glance

  • The complaint asserts representative claim 3, which depends on independent claim 1 (Compl. ¶47).
  • The essential elements of independent claim 1 and dependent claim 3 combined are:
    • A device for enhancing periodicity of an excitation signal produced in relation to a pitch codevector and an innovative codevector for supplying a signal synthesis filter in view of synthesizing a wideband speech signal.
    • A factor generator for calculating a periodicity factor related to the wideband speech signal.
    • An innovation filter for filtering the innovative codevector in relation to the periodicity factor to thereby reduce energy of a low frequency portion of the innovative codevector and enhance periodicity of a low frequency portion of the excitation signal.
    • Wherein the innovation filter has a transfer function of the form F(z) = -az + 1 – az⁻¹, where a is a periodicity factor derived from a level of periodicity of the excitation signal.

U.S. Patent No. 6,807,524 - "Perceptual Weighting Device and Method for Efficient Coding of Wideband Signals"

The Invention Explained

  • Problem Addressed: The patent identifies a limitation in traditional perceptual weighting filters used in CELP-type speech coders when applied to wideband signals. These filters struggled to concurrently model both the formant structure (vocal tract resonances) and the pronounced spectral tilt (energy difference between low and high frequencies) characteristic of wideband speech (U.S. US6807524B1, col. 2:50-57).
  • The Patented Solution: The invention proposes a new structure that first applies a pre-emphasis filter to the input signal to enhance high frequencies. The Linear Prediction (LP) analysis is then performed on this pre-emphasized signal. This is combined with a modified perceptual weighting filter that has a fixed denominator, which decouples the shaping of the formant structure from the control of the spectral tilt (U.S. 6,807,524 B1, Abstract; col. 3:9-20).
  • Technical Importance: This decoupling allowed for more accurate and efficient perceptual weighting of quantization error in wideband codecs, leading to higher subjective quality in the decoded audio and enabling simpler fixed-point algorithmic implementation (U.S. 6,807,524 B1, col. 4:1-4).

Key Claims at a Glance

  • The complaint asserts representative claim 4 (Compl. ¶63).
  • The essential elements of independent claim 4 are:
    • A perceptual weighting device for producing a perceptually weighted signal in response to a wideband speech signal.
    • A signal preemphasis filter responsive to the wideband speech signal for enhancing its high frequency content to produce a preemphasised signal.
    • A synthesis filter calculator responsive to the preemphasised signal for producing synthesis filter coefficients.
    • A perceptual weighting filter, responsive to the preemphasised signal and synthesis filter coefficients, for filtering the preemphasised signal.
    • Wherein the perceptual weighting filter has a transfer function with a fixed denominator, whereby weighting of the wideband speech signal in a formant region is substantially decoupled from a spectral tilt of the signal.
    • Wherein the preemphasis filter has a transfer function of the form P(z) = 1 − μz⁻¹, and the perceptual weighting filter has a transfer function of the form W(z) = A(z/γ1)/(1 – y2z¯¹).

U.S. Patent No. 7,151,802 - "High Frequency Content Recovering Method and Device for Over-Sampled Synthesized Wideband Signal"

Technology Synopsis

This patent addresses the problem of restoring high-frequency content that is lost when a wideband audio signal is down-sampled for efficient encoding (U.S. US7151802B1, col. 1:9-15). The solution involves generating a random noise sequence, spectrally shaping it based on the characteristics of the decoded lower-band signal, and injecting this shaped noise into the up-sampled signal to create a full-spectrum output (U.S. 7,151,802 B1, Abstract).

Asserted Claims

Representative claim 1 is asserted (Compl. ¶80).

Accused Features

The complaint alleges that the EVS Codec's high-frequency content recovering device, which generates, shapes, and injects a noise sequence to produce a full-spectrum signal, infringes the ’802 Patent (Compl. ¶¶ 85-87).

U.S. Patent No. 7,260,521 - "Method and Device for Adaptive Bandwidth Pitch Search in Coding Wideband Signals"

Technology Synopsis

This patent describes a method for more efficiently modeling the harmonic structure (pitch) in wideband speech, which often does not extend across the entire spectrum (U.S. US7260521B1, col. 2:5-12). The invention uses multiple signal paths, at least one of which includes a filter, to analyze the pitch contribution. It then selects the path that results in the lowest pitch prediction error, allowing the system to adaptively model the pitch bandwidth (U.S. 7,260,521 B1, Abstract).

Asserted Claims

Representative claim 2 is asserted (Compl. ¶96).

Accused Features

The complaint alleges infringement by the EVS Standard's pitch analysis device, which uses at least two signal paths—one with a filter and one without—and a selector to choose the path with the lowest prediction error (Compl. ¶¶ 103-106).

U.S. Patent No. 7,191,123 - "Gain-Smoothing in Wideband Speech and Audio Signal Decoder"

Technology Synopsis

The patent addresses degraded audio quality in synthesized speech when stationary background noise is present (U.S. US7191123B1, col. 2:22-26). The solution is a gain-smoothing device that modifies the gain of the innovative codevector based on factors representing the "voicing" of the speech signal and the "stability" of the linear prediction filter coefficients. This reduces energy fluctuations during stationary noise, improving perceived quality (U.S. 7,191,123 B1, Abstract).

Asserted Claims

Representative claim 102 is asserted (Compl. ¶115).

Accused Features

The EVS Standard's device for producing a gain-smoothed codevector is accused. This device allegedly calculates a smoothing gain using a non-linear operation based on a "voicing representative factor" and applies it to the codevector (Compl. ¶¶ 120-124).

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are "LG EVS Products," defined as any LG mobile device, including smartphones and tablets, that contains the EVS Codec (Compl. ¶45). The complaint lists numerous specific models, such as the LG V30, LG G6, and LG G7 ThinQ, as well as devices containing specific Qualcomm Snapdragon or MediaTek modems (Compl. ¶¶ 45, 61, 78, 94, 113).

Functionality and Market Context

The accused products are alleged to implement the EVS Standard to provide "Ultra HD Voice" or "HD Voice+" services over LTE networks (Compl. ¶¶ 25, 45). This standard and functionality are positioned as a key feature for mobile devices, enabling improved voice quality, higher compression efficiency, and enhanced resilience to network errors compared to previous codecs (Compl. ¶30). The complaint alleges that any mobile device marketed as "HD Voice+" capable must support the EVS Codec (Compl. ¶32). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

U.S. Patent No. 6,795,805 Infringement Allegations

Claim Element (from Independent Claim 1 and Dependent Claim 3) Alleged Infringing Functionality Complaint Citation Patent Citation
a device for enhancing periodicity of an excitation signal produced in relation to a pitch codevector and an innovative codevector... The EVS Standard includes devices for enhancing the periodicity of an excitation signal produced from pitch and innovative codevectors. ¶52 col. 2:30-37
said periodicity enhancing device comprising a factor generator for calculating a periodicity factor related to the wideband speech signal; The EVS Standard's periodicity enhancing device comprises a factor generator for calculating a periodicity factor. ¶53 col. 2:43-46
and an innovation filter for filtering the innovative codevector...to thereby reduce energy of a low frequency portion...and enhance periodicity of a low frequency portion... The EVS Standard's device includes an innovation filter that filters the innovative codevector to reduce low-frequency energy and enhance low-frequency periodicity. ¶53 col. 2:47-53
wherein said innovation filter has a transfer function of the form F(z) = -az + 1 – az⁻¹ where a is a periodicity factor... The innovation filter in the EVS Standard has a transfer function of the form F(z) = -az + 1 – az⁻¹, where 'a' is a periodicity factor. ¶54 col. 2:56-60
  • Identified Points of Contention:
    • Scope Questions: A central question will be whether the functions described in the EVS Standard sections cited by the complaint perform the specific actions required by the claim. For example, does the filter in the EVS Standard operate on the "innovative codevector" to "reduce energy" and "enhance periodicity" of specific portions of the signal in the manner claimed, or does it achieve a similar result through a technically distinct operation?
    • Technical Questions: The analysis may focus on the calculation of the "periodicity factor." The court will need to determine if the method for deriving this factor in the accused EVS Codec is the same as, or equivalent to, that disclosed in the ’805 Patent specification.

U.S. Patent No. 6,807,524 Infringement Allegations

Claim Element (from Independent Claim 4) Alleged Infringing Functionality Complaint Citation Patent Citation
a signal preemphasis filter responsive to the wideband speech signal for enhancing a high frequency content...to thereby produce a preemphasised signal; The EVS Standard's perceptual weighting device comprises a signal preemphasis filter that enhances the high-frequency content of the wideband signal. ¶69 col. 3:6-10
a synthesis filter calculator responsive to said preemphasised signal for producing synthesis filter coefficients; The EVS Standard's device includes a synthesis filter calculator responsive to the preemphasised signal. ¶69 col. 3:11-13
a perceptual weighting filter...for filtering said preemphasised signal in relation to said synthesis filter coefficients... The EVS Standard's device includes a perceptual weighting filter responsive to the preemphasised signal and synthesis filter coefficients. ¶69 col. 3:14-18
said perceptual weighting filter having a transfer function with fixed denominator whereby weighting...is substantially decoupled from a spectral tilt... The perceptual weighting filter in the EVS Standard is alleged to have a transfer function with a fixed denominator, which substantially decouples formant weighting from spectral tilt. ¶69 col. 3:18-24
  • Identified Points of Contention:
    • Scope Questions: The term "substantially decoupled" will be a key point of dispute. The infringement analysis will likely require expert testimony to determine whether the degree of decoupling achieved by the EVS Standard's filter meets this claim limitation as understood in the context of the patent.
    • Technical Questions: The case may turn on whether the accused devices perform LP analysis on a pre-emphasized signal, as required by the patent's described solution for achieving decoupling. A defendant might argue their implementation calculates filter coefficients in a different manner that does not rely on this specific sequence of operations.

V. Key Claim Terms for Construction

  • Patent: ’805 Patent

    • The Term: "innovation filter for filtering the innovative codevector... to thereby reduce energy of a low frequency portion... and enhance periodicity of a low frequency portion"
    • Context and Importance: This functional language is at the heart of the claim. Infringement will depend on whether the accused filter in the EVS standard performs this specific dual function (reducing energy AND enhancing periodicity) on the specified signal portion. Practitioners may focus on whether the term requires two distinct outcomes or if a single filtering operation that results in both is sufficient.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The "Summary of the Invention" describes the filter's role more generally as altering the innovative codevector "to thereby reduce energy of a low frequency portion of the innovative codevector and enhance periodicity of a low frequency portion of the excitation signal" (U.S. 6,795,805 B1, col. 2:38-42).
      • Evidence for a Narrower Interpretation: The detailed description links this function to specific transfer function equations, such as F(z)=-az+1-az⁻¹, suggesting the function is defined by this specific mathematical implementation (U.S. 6,795,805 B1, col. 2:56-60).

  • Patent: ’524 Patent

    • The Term: "substantially decoupled from a spectral tilt"
    • Context and Importance: This term defines the primary technical benefit of the invention. The outcome of the case could depend entirely on the degree of "decoupling" required to meet this limitation. The parties will likely dispute what technical measurement or threshold constitutes "substantial" decoupling.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The patent's background criticizes prior art where formant structure and spectral tilt are modeled "concurrently," suggesting "decoupled" means not modeled at the same time or by the same filter components (U.S. 6,807,524 B1, col. 2:54-57).
      • Evidence for a Narrower Interpretation: The specification explicitly links the decoupling to the use of a "fixed denominator" in the weighting filter's transfer function, specifically W(z)=A(z/γ1)/(1-y2z⁻¹) (U.S. 6,807,524 B1, col. 3:18-24). A defendant may argue that only a filter with this specific structure can achieve the claimed decoupling.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for all five patents-in-suit. The basis for these allegations is that LG advertises, promotes, and sells the accused products with the specific intent that end-users will use the EVS functionality in an infringing manner. The complaint further asserts that the EVS Codec as implemented has no substantial non-infringing uses (Compl. ¶¶ 55, 72, 88, 107, 125).
  • Willful Infringement: Willfulness is alleged for all asserted patents. The complaint bases this on LG's alleged actual, pre-suit knowledge of the patents from several sources, including: (1) prior litigation where the same patents were asserted against LG (Case No. 2:14-cv-01055-JRG); (2) public information regarding the patents and their relation to the EVS standard; and (3) direct notice from the patent owner (Compl. ¶¶ 36, 37, 57, 74, 90, 109, 127).

VII. Analyst’s Conclusion: Key Questions for the Case

  • Standard-Essentiality and Claim Scope: A central issue will be whether compliance with the relevant sections of the 3GPP EVS Standard, as alleged, necessarily infringes the asserted claims. This will involve a technical deep-dive into whether the operations mandated by the standard fall within the scope of key claim limitations, such as the "fixed denominator" of the ’524 patent or the specific filtering function of the ’805 patent.
  • Preclusion and Validity: A threshold procedural question will be the legal effect of the prior litigation between the parties. The court will need to determine whether LG's previous invalidity counterclaims, which were allegedly dismissed with prejudice, estop it from challenging the validity of the patents-in-suit in this case.
  • Damages and Licensing: Given the alleged prior license agreement concerning the AMR-WB standard, a key question for damages will be the proper scope and methodology for calculating a reasonable royalty for infringement by the separate EVS standard, and to what extent, if any, the prior agreement informs that analysis.