DCT

2:25-cv-00460

VoiceAge EVS LLC v. OnePlus Technology Shenzhen Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:25-cv-00460, E.D. Tex., 05/01/2025
  • Venue Allegations: Plaintiff alleges venue is proper because Defendant is a foreign corporation that may be sued in any judicial district, regularly conducts business in the district through website sales, and has previously consented to jurisdiction in the Eastern District of Texas. The complaint also notes sales through T-Mobile and BestBuy retail stores located within the district.
  • Core Dispute: Plaintiff alleges that Defendant’s mobile devices implementing the Enhanced Voice Services (EVS) audio codec standard infringe six patents related to foundational audio coding technologies.
  • Technical Context: The technology concerns audio codecs for mobile telecommunications, which compress and decompress voice signals to balance high-quality audio with efficient use of limited network bandwidth.
  • Key Procedural History: The complaint alleges that the patents-in-suit are essential to the EVS standard, have been licensed to eleven major handset manufacturers, and have had their validity and infringement upheld in foreign litigation in Germany and Brazil against Defendant’s corporate affiliates. Plaintiff also alleges it provided Defendant with actual notice of the patents in a letter dated February 3, 2020.

Case Timeline

Date Event
2002-05-31 ’710 Patent Priority Date
2006-10-24 ’843 Patent Priority Date
2007-06-22 ’073 Patent Priority Date
2010-04-06 ’710 Patent Issue Date
2010-10-25 ’038 Patent Priority Date
2011-05-11 ’475 Patent Priority Date
2013-03-19 ’843 Patent Issue Date
2014-04-17 ’741 Patent Priority Date
2014-09-02 ’475 Patent Issue Date
2015-03-24 ’073 Patent Issue Date
2015-04-21 ’038 Patent Issue Date
2016-01-01 T-Mobile announces network upgrade to support EVS (approx. date)
2017-12-26 ’741 Patent Issue Date
2018-12-05 Plaintiff VoiceAge EVS acquires patent portfolio from VoiceAge Corporation
2019-07-26 IPEC Declarations of Essentiality for asserted patents made available online
2020-02-03 Plaintiff sends letter to Defendant identifying patent portfolio
2020-02-11 Plaintiff receives proof of delivery for its letter to Defendant
2025-05-01 Complaint Filing Date

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

U.S. Patent No. 7,693,710 - “Method and device for efficient frame erasure concealment in linear predictive based speech codecs”

The Invention Explained

  • Problem Addressed: In digital communication systems like wireless networks, packets of audio data (frames) can be lost or "erased" during transmission, which significantly degrades sound quality (Compl. ¶¶87-88). When a frame is lost, the decoder at the receiving end becomes "desynchronized" from the encoder, as it lacks the correct information to predict the next sound, an effect that is amplified when multiple consecutive frames are erased (’710 Patent, col. 2:10-17, col. 11:38-57).
  • The Patented Solution: The invention proposes that the encoder analyze the outgoing speech signal and determine specific "concealment/recovery parameters" for each frame, such as a classification of the frame type (e.g., voiced, unvoiced, transition) and information about signal energy and phase (Compl. ¶91; ’710 Patent, col. 12:65-13:2). These parameters are then transmitted to the decoder. If a frame is erased, the decoder uses these pre-supplied parameters from the last good frame to more intelligently conceal the missing audio and resynchronize more quickly once good frames are received again (Compl. ¶¶89-90; ’710 Patent, col. 2:58-3:48).
  • Technical Importance: This method provides a more robust way to handle the inevitable packet loss in mobile and voice-over-IP networks, improving the perceived quality and reliability of calls (Compl. ¶86).

Key Claims at a Glance

  • The complaint asserts independent claims 16 and 24 (Compl. ¶162).
  • Key elements of independent device claim 16 include:
    • A device for conducting concealment of frame erasure.
    • An encoder component comprising a "determiner" of concealment/recovery parameters, where the parameters are selected from a group including a signal classification parameter, an energy information parameter, and a phase information parameter.
    • A communication link to transmit these parameters to a decoder.
    • A decoder that conducts concealment and recovery in response to the received parameters.
    • The determiner further comprises a "classifier" that categorizes successive frames as one of five types: unvoiced, unvoiced transition, voiced transition, voiced, or onset.
    • The determiner also comprises a "computer" for the energy information parameter, calculated differently for frames classified as voiced/onset versus other frames.

U.S. Patent No. 8,401,843 - “Method and device for coding transition frames in speech signals”

The Invention Explained

  • Problem Addressed: Codecs using Code-Excited Linear Prediction (CELP) rely heavily on past audio information to encode the current audio frame. When a transmission error erases a frame, the decoder loses this historical context, causing desynchronization. The effect of the error then "propagate[s]" through subsequent frames, creating a perceptually "very annoying" audio artifact (Compl. ¶97; ’843 Patent, col. 2:10-17).
  • The Patented Solution: The patent discloses a "transition mode" (TM) encoding technique. For transition frames (e.g., a shift from unvoiced to voiced sound), the system replaces the standard predictive codebook with a "glottal-shape codebook" that is fixed and "independent of the past excitation" (Compl. ¶¶98-99; ’843 Patent, col. 5:59-6:5). Because this special codebook does not rely on prior frames, the encoder and decoder can immediately re-synchronize after a frame erasure by using the same, shared excitation source, which "eliminate[s] error propagation" (Compl. ¶99; ’843 Patent, col. 2:56-62).
  • Technical Importance: The invention improves a codec's robustness against transmission errors in critical transition frames without adding delay, complexity, or increasing the bit rate, which are crucial constraints for real-time voice communications (Compl. ¶99).

Key Claims at a Glance

  • The complaint asserts independent claims 11 and 14 (Compl. ¶174).
  • Key elements of independent device claim 11 include:
    • A device for generating a transition mode excitation that replaces an adaptive codebook excitation in a transition frame.
    • A generator for a codebook search target signal.
    • A "transition mode codebook" for generating codevectors that are "independent from past excitation."
    • The transition mode codebook comprises a "codebook of glottal impulse shapes."
    • A searcher that finds the optimal codevector from the transition mode codebook corresponding to the target signal.

U.S. Patent No. 8,990,073 - “Method and device for sound activity detection and sound signal classification”

  • Technology Synopsis: The patent addresses the technical problem of sound activity detection (SAD), particularly distinguishing between useful signals (like speech or music) and background noise (Compl. ¶102). The solution involves estimating the "tonal stability" of a sound signal to improve the performance of a SAD algorithm, helping to better discriminate between unvoiced sounds and music signals (’073 Patent, Abstract; Compl. ¶103).
  • Asserted Claims: Independent claims 31 and 36 (Compl. ¶186).
  • Accused Features: The complaint alleges that OnePlus's EVS Products, by complying with the EVS Standard, are capable of detecting sound activity and estimating tonal stability as claimed (Compl. ¶186).

U.S. Patent No. 8,825,475 - “Transform-domain codebook in a CELP coder and decoder”

  • Technology Synopsis: The patent addresses the problem that while the ACELP model is efficient at low bit rates, its quality does not improve as quickly as other methods when bit rates increase (Compl. ¶108). The solution modifies the CELP model by adding a "transform-domain codebook stage" and a selector that can change the order of the codebook stages based on characteristics of the input signal and the bit rate, allowing for better control over how additional bits are used across different frequencies (’475 Patent, Abstract; Compl. ¶109).
  • Asserted Claims: Independent claims 1 and 3 (Compl. ¶198).
  • Accused Features: The complaint alleges that OnePlus's EVS Products perform encoding and decoding using a CELP codebook structure with a selectable order for innovative and transform-domain stages as claimed (Compl. ¶¶199-200).

U.S. Patent No. 9,852,741 - “Methods, encoder and decoder for linear predictive encoding and decoding of sound signals upon transition between frames having different sampling rates”

  • Technology Synopsis: The patent addresses the technical challenge of switching between different bit rates that use different internal sampling rates in a multi-rate coder without introducing audible artifacts (Compl. ¶114). The solution provides a computationally efficient method for converting linear predictive (LP) filter parameters between different sampling rates by modifying the power spectrum of the LP filter, avoiding the need to re-sample the past synthesis signal (’741 Patent, Abstract; Compl. ¶116).
  • Asserted Claims: Independent claims 17 and 20 (Compl. ¶210).
  • Accused Features: The complaint alleges that OnePlus's EVS Products are capable of encoding sound signals by converting LP filter parameters between different internal sampling rates (S1 and S2) by extending or truncating the power spectrum as claimed (Compl. ¶¶211-212).

U.S. Patent No. 9,015,038 - “Coding generic audio signals at low bitrates and low delay”

  • Technology Synopsis: The patent addresses the problem that low-delay conversational codecs are often unsuitable for generic audio like music, while "switched codecs" that use different approaches for speech and music typically require longer processing delays (Compl. ¶¶120-121). The solution uses a "more unified time-domain and frequency-domain model" that combines contributions from both domains to improve encoding quality for a mix of input signals (’038 Patent, col. 1:35-36; Compl. ¶122).
  • Asserted Claims: Independent claims 1 and 2 (Compl. ¶222).
  • Accused Features: The complaint alleges that OnePlus's EVS Products are a mixed time-domain/frequency-domain coding device that calculates and combines contributions from both domains as claimed (Compl. ¶¶223-224).

III. The Accused Instrumentality

Product Identification

The complaint identifies the accused instrumentalities as "OnePlus's EVS Products," which are mobile devices with EVS codec capabilities compliant with the EVS Standard, including but not limited to the OnePlus 9 and OnePlus 13 (Compl. ¶124).

Functionality and Market Context

The accused products are mobile devices that include hardware and software implementing the EVS codec (Compl. ¶126). This functionality allows for higher-quality voice calls over modern wireless networks, marketed under terms such as "Enhanced HD Voice" or "Ultra HD Voice" (Compl. ¶12, ¶126). The complaint alleges that the EVS codec is an improvement over the prior AMR-WB standard by offering more than double the spectral bandwidth. The complaint provides a diagram comparing the frequency ranges of traditional AMR, AMR-WB, and EVS codecs to illustrate this technical advancement (Compl. ¶10, Diagram p. 4). The complaint further alleges that the patents-in-suit are essential to the EVS standard, meaning any device compliant with the standard necessarily uses the patented technology (Compl. ¶127).

IV. Analysis of Infringement Allegations

’710 Patent Infringement Allegations

Claim Element (from Independent Claim 16) Alleged Infringing Functionality Complaint Citation Patent Citation
a device for conducting concealment of frame erasure... The accused OnePlus 9 and OnePlus 13 are devices with hardware and software implementing the EVS codec, which is capable of performing concealment of frame erasure. ¶162-163 col. 2:58-63
in the encoder, a determiner of concealment/recovery parameters selected from the group consisting of a signal classification parameter, an energy information parameter and a phase information parameter... The EVS codec in the accused products determines concealment/recovery parameters as described in 3GPP standards document TS 26.445 §§ 4.1, 4.4, and 5.5. ¶163 col. 11:58-12:5
a communication link for transmitting to the decoder concealment/recovery parameters determined in the encoder... The accused devices transmit these parameters from the encoder to the decoder over a communication link as part of standard EVS operation. ¶163 col. 3:25-28
the determiner of concealment/recovery parameters comprises a classifier of successive frames of the encoded sound signal as unvoiced, unvoiced transition, voiced transition, voiced, or onset... The EVS codec in the accused products classifies frames into successive types, including those corresponding to unvoiced, voiced, and transition states, consistent with the standard. ¶163 col. 13:38-50
the determiner of concealment/recovery parameters comprises a computer of the energy information parameter in relation to a maximum of a signal energy for frames classified as voiced or onset, and in relation to an average energy per sample for other frames. The EVS codec in the accused products computes an energy parameter based on a maximum signal energy for voiced/onset frames and average energy for other frames, as specified in the standard. ¶163 col. 22:2-37
  • Identified Points of Contention:
    • Scope Questions: A central question may be whether the term "classifier of successive frames of the encoded sound signal as unvoiced, unvoiced transition, voiced transition, voiced, or onset" reads on the specific signal classification scheme implemented in the EVS standard. The defense may argue that the standard's classification, while functional, differs in material ways from the five specific classes required by the claim.
    • Technical Questions: The analysis will likely focus on whether the EVS standard's method for calculating and using an "energy information parameter" is technically equivalent to the specific two-part calculation ("in relation to a maximum of a signal energy" for some frames and "in relation to an average energy per sample" for others) required by the claim language.

’843 Patent Infringement Allegations

Claim Element (from Independent Claim 11) Alleged Infringing Functionality Complaint Citation Patent Citation
a device for generating a transition mode excitation replacing an adaptive codebook excitation in a transition frame... The accused OnePlus 9 and OnePlus 13 are devices implementing the EVS codec, which is capable of generating a transition mode excitation as described in 3GPP TS 26.445 §§ 4.1, 4.4, 5.1, and 5.2. ¶174-175 col. 2:51-55
a generator of a codebook search target signal... The EVS codec in the accused products generates a target signal for the codebook search as part of its standard encoding process. ¶175 col. 5:28-36
a transition mode codebook for generating a set of codevectors independent from past excitation... The EVS codec in the accused products uses a codebook for transition frames that is not dependent on the past excitation signal, to prevent error propagation. ¶175 col. 5:59-6:5
wherein the transition mode codebook comprises a codebook of glottal impulse shapes... The complaint alleges that the transition mode codebook used in the EVS standard corresponds to a codebook of glottal impulse shapes as claimed. ¶175 col. 5:59-64
a searcher of the transition mode codebook for finding the codevector...optimally corresponding to the codebook search target signal. The EVS codec in the accused devices includes a searcher function to find the optimal codevector from the transition mode codebook that best matches the target signal. ¶175 col. 6:6-14
  • Identified Points of Contention:
    • Scope Questions: A likely point of dispute will be the construction of "transition mode codebook" and "codebook of glottal impulse shapes." The court will need to determine if the specific codebooks and techniques for handling transition frames within the EVS standard fall within the scope of these claim terms.
    • Technical Questions: A key technical question is whether the codebook used for transition frames in the accused products is truly "independent from past excitation" in the manner required by the claim, or if there is some residual dependency that takes it outside the claim scope.

V. Key Claim Terms for Construction

For the ’710 Patent:

  • The Term: "classifier of successive frames...as unvoiced, unvoiced transition, voiced transition, voiced, or onset" (Claim 16).
  • Context and Importance: This term is critical because infringement hinges on whether the accused devices perform this specific five-part classification. The defendant will likely argue that the EVS standard uses a different, non-infringing classification scheme, making the precise scope of this term dispositive.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification describes the classes as part of a general strategy, stating that for error concealment, "some of the signal classes are grouped together" (’710 Patent, col. 13:33-35). This may support an argument that the exact five-part list is illustrative, not strictly limiting.
    • Evidence for a Narrower Interpretation: The detailed description explicitly defines these five distinct classes and links them to specific concealment and recovery strategies (’710 Patent, col. 13:59-14:30). The patent examiner explicitly cited the novelty of classifying frames into these specific categories as a reason for allowance (Compl. ¶93), suggesting the specific list is a key limitation.

For the ’843 Patent:

  • The Term: "transition mode codebook" (Claim 11).
  • Context and Importance: This is the core inventive concept. Its definition will determine whether the special codebook used for transition frames in the EVS standard infringes. Practitioners may focus on whether this term requires a complete replacement of the adaptive codebook or if it can cover a supplemental or alternative codebook.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent states a general object is to "replace the inter-frame dependent adaptive codebook search by a non-predictive...codebook search" (’843 Patent, col. 2:56-60), which could support a broader reading on any codebook that serves this non-predictive function in a transition frame.
    • Evidence for a Narrower Interpretation: The specification consistently links the "transition mode" to a specific solution: "a new codebook of glottal impulse shapes, hereinafter designated as glottal-shape codebook" (’843 Patent, col. 5:62-64). The patent examiner's allowance was based on the novelty of "a transition mode codebook... compris[ing] a codebook of glottal impulse shapes" (Compl. ¶100), suggesting the terms are tightly linked.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges inducement of infringement by asserting that OnePlus provides customers with user guides and repair manuals that include instructions on how to make a phone call. Performing this action on an EVS-supported network with an accused device allegedly causes direct infringement by the end-user, which OnePlus encourages and facilitates (Compl. ¶¶154-156, 168-169).
  • Willful Infringement: Willfulness is alleged based on pre-suit and post-suit knowledge. The complaint alleges OnePlus had actual knowledge at least as of February 11, 2020, upon receiving a letter from VoiceAge EVS (Compl. ¶130). It further alleges knowledge based on OnePlus's participation in the 3GPP standards body, the public availability of IPEC Declarations of Essentiality for the patents on Plaintiff's website since July 2019, and ongoing foreign litigation against OnePlus affiliates involving counterparts to the asserted patents (Compl. ¶¶62, 67-71, 134-141). The complaint presents a screenshot of an IPEC declaration for the '710 patent as an example of the public notice available to OnePlus (Compl. ¶70, Image p. 16).

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

  • A central issue will be one of standard-essentiality and claim construction: can Plaintiff prove that compliance with the 3GPP EVS standard, as implemented in the accused products, necessarily infringes the asserted patent claims? This will require the court to construe key claim terms, such as the specific frame "classifier" in the ’710 patent and the "transition mode codebook" of the ’843 patent, and then map those constructions onto the technical operation of the EVS codec.
  • A key evidentiary question will be one of technical equivalence: assuming the EVS standard does not map literally onto every claim element, does the functionality of the accused products perform substantially the same function in substantially the same way to achieve the same result as the claimed inventions? For instance, does the standard's method for handling packet loss achieve concealment and recovery in a way that is technically equivalent to the specific five-class system claimed in the ’710 patent?
  • A third major issue will be willfulness: given the complaint's detailed allegations of pre-suit notice via letter, public essentiality declarations, and knowledge of foreign litigation against affiliates, a critical question for the fact-finder will be whether OnePlus's alleged continued infringement after notice was objectively reckless, potentially justifying enhanced damages.