Patent 6807524

Prior art

Earlier patents, publications, and products that may anticipate or render the claims unpatentable.

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Prior art

Earlier patents, publications, and products that may anticipate or render the claims unpatentable.

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To identify the most relevant prior art for US patent 6807524, I will perform a search of its cited references. Since the patent has expired, new litigation related to infringement is highly unlikely, but understanding its prior art is still crucial for historical analysis and understanding the patent's scope.

Here's an analysis of the prior art cited in US Patent 6,807,524, focusing on full citation, publication/filing date, brief description, and which claim(s) it potentially anticipates under 35 U.S.C. § 102.

Prior Art Analysis for US6807524B1

US Patent 6,807,524 (hereinafter '524 patent) addresses improvements in perceptual weighting for efficient coding of wideband signals, specifically focusing on decoupling formant weighting from spectral tilt using a pre-emphasis filter and a modified perceptual weighting filter with a fixed denominator. The patent's specification and claims highlight this specific approach.

Cited Prior Art References:

  1. US4932061A

    • Full Citation: US4932061A, "Multi-pulse excitation linear-predictive speech coder" to U.S. Philips Corporation.
    • Publication/Filing Date: Filed March 22, 1985; Published June 5, 1990.
    • Brief Description: This patent describes a multi-pulse excitation linear predictive (MPELP) speech coder. It focuses on generating an excitation signal using multiple pulses and then filtering it through a linear predictive synthesis filter to reconstruct speech. It's a foundational patent in linear predictive coding (LPC) and excitation source modeling for speech.
    • Potential Anticipation (35 U.S.C. § 102): US4932061A would primarily anticipate broader concepts of linear predictive coding and the use of synthesis filters in speech encoding, as generally discussed in the background of the '524 patent. Claims 1, 8, and 15, while building on CELP principles (a type of LPC), introduce specific modifications to perceptual weighting for wideband signals using a fixed-denominator weighting filter and pre-emphasis. Therefore, while it establishes the prior art context, it is unlikely to directly anticipate the specific perceptual weighting filter with a fixed denominator for wideband signals or the decoupling of formant weighting from spectral tilt as claimed in the '524 patent.

  2. US5307441A

    • Full Citation: US5307441A, "Near-toll quality 4.8 kbps speech codec" to Comsat Corporation.
    • Publication/Filing Date: Filed November 29, 1989; Published April 26, 1994.
    • Brief Description: This patent describes a low bit-rate speech codec designed for near-toll quality. It likely involves various speech coding techniques, possibly including CELP or related LPC schemes, to achieve efficient compression at low bit rates.
    • Potential Anticipation (35 U.S.C. § 102): Similar to US4932061A, this patent would likely establish prior art for general speech coding systems and low bit-rate codecs, particularly within the CELP framework. However, the '524 patent's inventive step lies in its specific perceptual weighting scheme for wideband signals. Therefore, US5307441A would likely not anticipate the specific features of the perceptual weighting filter and its interaction with pre-emphasis as defined in claims 1, 8, and 15, especially concerning the fixed denominator and decoupling of formant and tilt weighting for wideband signals.

  3. US5359696A

    • Full Citation: US5359696A, "Digital speech coder having improved sub-sample resolution long-term predictor" to Motorola Inc.
    • Publication/Filing Date: Filed June 28, 1988; Published October 25, 1994.
    • Brief Description: This patent focuses on improving the pitch prediction in a digital speech coder by using sub-sample resolution in the long-term predictor. This improves the accuracy of representing the periodic components of speech. The '524 patent also mentions the use of higher pitch resolution in its detailed description.
    • Potential Anticipation (35 U.S.C. § 102): US5359696A directly relates to the pitch analysis aspect of speech coding, specifically the use of sub-sample pitch resolution. This could potentially anticipate aspects of the pitch codebook search device mentioned in claim 15 of the '524 patent, particularly if the implementation of "higher pitch resolution" in the '524 patent's pitch codebook search module 107 (as described in the detailed description) is found to be directly taught or rendered obvious by US5359696A. However, it does not appear to address the core perceptual weighting filter innovation of claims 1 and 8.

  4. US5444816A

    • Full Citation: US5444816A, "Dynamic codebook for efficient speech coding based on algebraic codes" to Universite De Sherbrooke.
    • Publication/Filing Date: Filed February 23, 1990; Published August 22, 1995.
    • Brief Description: This patent describes an algebraic codebook used for efficient speech coding. Algebraic codebooks are a specific type of innovative codebook often used in CELP encoders. The '524 patent explicitly references this patent (and others by Adoul et al.) for its innovative codebook search.
    • Potential Anticipation (35 U.S.C. § 102): US5444816A would clearly anticipate the concept of an "innovative codebook search device" and the use of algebraic codebooks, as referenced in claim 15 of the '524 patent. The '524 patent's encoder (claim 15) incorporates such a device, and the specific details of the algebraic codebook itself would be anticipated by this prior art. However, it does not anticipate the novel perceptual weighting device or method.

  5. US5664055A

    • Full Citation: US5664055A, "CS-ACELP speech compression system with adaptive pitch prediction filter gain based on a measure of periodicity" to Lucent Technologies Inc.
    • Publication/Filing Date: Filed June 7, 1995; Published September 2, 1997.
    • Brief Description: This patent describes a CS-ACELP (Conjugate Structure Algebraic CELP) system that adaptively adjusts the pitch prediction filter gain based on a measure of speech periodicity. This relates to how pitch information is used to enhance speech quality.
    • Potential Anticipation (35 U.S.C. § 102): US5664055A would likely anticipate aspects related to adaptive pitch prediction gain and periodicity measures within a CELP framework, which is relevant to the "pitch codebook search device" of claim 15 in the '524 patent. While the '524 patent also discusses periodicity enhancement at the decoder, this prior art primarily focuses on the encoder side's pitch prediction. It does not appear to anticipate the unique perceptual weighting filter of claims 1 and 8.

  6. US5701392A

    • Full Citation: US5701392A, "Depth-first algebraic-codebook search for fast coding of speech" to Universite De Sherbrooke.
    • Publication/Filing Date: Filed February 23, 1990; Published December 23, 1997.
    • Brief Description: This patent describes an improved search method (depth-first) for an algebraic codebook to achieve faster speech coding. It's an optimization of the innovative codebook search process. The '524 patent explicitly references this patent as well.
    • Potential Anticipation (35 U.S.C. § 102): Similar to US5444816A, this patent would anticipate the specific search methodology for the innovative codebook within the "innovative codebook search device" of claim 15 of the '524 patent. Again, it does not anticipate the distinct perceptual weighting device or method.

  7. US5754976A

    • Full Citation: US5754976A, "Algebraic codebook with signal-selected pulse amplitude/position combinations for fast coding of speech" to Universite De Sherbrooke.
    • Publication/Filing Date: Filed February 23, 1990; Published May 19, 1998.
    • Brief Description: This patent describes another variation of an algebraic codebook, focusing on how pulse amplitudes and positions are selected to improve speech coding efficiency. This further refines the innovative codebook concept. The '524 patent explicitly references this patent.
    • Potential Anticipation (35 U.S.C. § 102): This patent, like the other Adoul et al. patents, would anticipate further details of the "innovative codebook search device" of claim 15, specifically the structure and operation of the algebraic codebook for speech coding. It does not anticipate the unique perceptual weighting device or method for wideband signals.

  8. US6006174A

    • Full Citation: US6006174A, "Multiple impulse excitation speech encoder and decoder" to Interdigital Technology Corporation.
    • Publication/Filing Date: Filed October 3, 1990; Published December 21, 1999.
    • Brief Description: This patent describes a speech encoder and decoder using multiple impulse excitation, which is a method for generating the excitation signal in speech coding. This is another variation of source modeling in LPC/CELP systems.
    • Potential Anticipation (35 U.S.C. § 102): This patent relates to the general principles of speech encoding and decoding, particularly concerning excitation models. While the '524 patent builds on these general principles (e.g., in its encoder claim 15), US6006174A does not appear to specifically teach or suggest the combination of a pre-emphasis filter with a fixed-denominator perceptual weighting filter for wideband signals to decouple formant and spectral tilt weighting, which is central to claims 1 and 8 of the '524 patent.

  9. US6064962A

    • Full Citation: US6064962A, "Formant emphasis method and formant emphasis filter device" to Kabushiki Kaisha Toshiba.
    • Publication/Filing Date: Filed September 14, 1995; Published May 16, 2000.
    • Brief Description: This patent describes a method and device for emphasizing formants in speech signals, which is a technique used to improve speech quality or intelligibility. Formant emphasis is related to perceptual weighting.
    • Potential Anticipation (35 U.S.C. § 102): This patent specifically addresses "formant emphasis," which is a key aspect of perceptual weighting. The '524 patent's claims 1 and 8 focus on a perceptual weighting filter that decouples formant weighting from spectral tilt using a fixed denominator. If US6064962A discloses a perceptual weighting filter that, explicitly or inherently, achieves this decoupling or uses a similar fixed-denominator structure in a way that anticipates the '524 patent's invention, it could be highly relevant. A detailed comparison of the transfer functions and their effects on wideband signals would be necessary to determine direct anticipation of claims 1 and 8.

  10. US6449590B1

    • Full Citation: US6449590B1, "Speech encoder using warping in long term preprocessing" to Conexant Systems, Inc.
    • Publication/Filing Date: Filed August 24, 1998; Published September 10, 2002.
    • Brief Description: This patent describes a speech encoder that uses warping in long-term pre-processing. Warping is a technique used to modify the frequency axis, which can be applied in various stages of speech coding, potentially affecting spectral characteristics or prediction.
    • Potential Anticipation (35 U.S.C. § 102): This patent's focus on "warping in long-term preprocessing" could be broadly relevant to signal processing within an encoder. However, it does not immediately appear to directly address the specific pre-emphasis filter and fixed-denominator perceptual weighting filter combination for decoupling formant and spectral tilt weighting in wideband signals, as claimed in claims 1 and 8 of the '524 patent. Its relevance would depend on whether the "warping" technique has an equivalent function to the specific perceptual weighting described in '524 for wideband signals.

Additional References Cited by the '524 Patent (non-patent literature):

The '524 patent also cites a non-patent literature reference:

  • B. S. Atal and M. R. Schroeder, "Predictive coding of speech and subjective error criteria", IEEE Transaction ASSP, vol. 27, no. 3, pp. 247-254, June 1979.
    • Publication Date: June 1979.
    • Brief Description: This is a seminal paper in speech coding, particularly related to linear predictive coding and the concept of minimizing perceptually weighted error. It is explicitly cited in the '524 patent for explaining how quantization error is weighted by the inverse of the weighting filter, and how this exploits the masking property of the human ear.
    • Potential Anticipation (35 U.S.C. § 102): This paper would establish foundational knowledge regarding perceptual weighting and error shaping in speech coding systems, specifically for telephone-band signals, as noted in the '524 patent's background. It sets the stage for the traditional weighting filter W(z) = A(z/γ₁)/A(z/γ₂) mentioned in the '524 patent. However, the '524 patent explicitly states that this traditional filter "is not suitable for efficient perceptual weighting when it was applied to wideband signals" and that it "has inherent limitations in modelling the formant structure and the required spectral tilt concurrently." Therefore, while the paper provides the theoretical basis for perceptual weighting, it would not anticipate the '524 patent's specific solution for wideband signals with a fixed-denominator perceptual weighting filter designed to decouple formant weighting from spectral tilt, as defined in claims 1 and 8.

Conclusion on Most Relevant Prior Art:

Based on the descriptions, US6064962A ("Formant emphasis method and formant emphasis filter device") appears to be potentially the most relevant patent prior art as it explicitly deals with "formant emphasis," which is a core function of perceptual weighting. A detailed comparison of its specific implementation and whether it achieves the claimed decoupling of formant weighting from spectral tilt using a fixed denominator for wideband signals would be critical.

The article by Atal and Schroeder (1979) is highly relevant for establishing the general state of the art in perceptual weighting in speech coding before the '524 patent. However, the '524 patent explicitly distinguishes its invention from the limitations of prior art weighting filters when applied to wideband signals.

For the encoder (claim 15), the patents US5444816A, US5701392A, and US5754976A (all by Adoul et al.) are directly cited and describe the innovative codebook search device using algebraic codebooks, which are explicitly incorporated into the '524 patent's encoder. Similarly, US5359696A is relevant for the pitch codebook search. While these references anticipate specific components within the encoder, they do not appear to anticipate the novel perceptual weighting aspects of claims 1 and 8 which are then integrated into the encoder of claim 15.

Generated 5/29/2026, 6:01:03 PM