Patents by Inventor Amitava Das

Amitava Das has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6820052
    Abstract: A low-bit-rate coding technique for unvoiced segments of speech includes the steps of extracting high-time-resolution energy coefficients from a frame of speech, quantizing the energy coefficients, generating a high-time-resolution energy envelope from the quantized energy coefficients, and reconstituting a residue signal by shaping a randomly generated noise vector with quantized values of the energy envelope. The energy envelope may be generated with a linear interpolation technique. A post-processing measure may be obtained and compared with a predefined threshold to determine whether the coding algorithm is performing adequately.
    Type: Grant
    Filed: July 17, 2002
    Date of Patent: November 16, 2004
    Assignee: Qualcomm Incorporated
    Inventors: Amitava Das, Sharath Manjunath
  • Patent number: 6754630
    Abstract: In a method of synthesizing voiced speech from pitch prototype waveforms by time-synchronous waveform interpolation (TSWI), one or more pitch prototypes is extracted from a speech signal or a residue signal. The extraction process is performed in such a way that the prototype has minimum energy at the boundary. Each prototype is circularly shifted so as to be time-synchronous with the original signal. A linear phase shift is applied to each extracted prototype relative to the previously extracted prototype so as to maximize the cross-correlation between successive extracted prototypes. A two-dimensional prototype-evolving surface is constructed by unsampling the prototypes to every sample point. The two-dimensional prototype-evolving surface is re-sampled to generate a one-dimensional, synthesized signal frame with sample points defined by piecewise continuous cubic phase contour functions computed from the pitch lags and the phase shifts added to the extracted prototypes.
    Type: Grant
    Filed: November 13, 1998
    Date of Patent: June 22, 2004
    Assignee: Qualcomm, Inc.
    Inventors: Amitava Das, Eddie L. T. Choy
  • Patent number: 6640209
    Abstract: A closed-loop, multimode, mixed-domain linear prediction (MDLP) speech coder includes a high-rate, time-domain coding mode, a low-rate, frequency-domain coding mode, and a closed-loop mode-selection mechanism for selecting a coding mode for the coder based upon the speech content of frames input to the coder. Transition speech (i.e., from unvoiced speech to voiced speech, or vice versa) frames are encoded with the high-rate, time-domain coding mode, which may be a CELP coding mode. Voiced speech frames are encoded with the low-rate, frequency-domain coding mode, which may be a harmonic coding mode. Phase parameters are not encoded by the frequency-domain coding mode, and are instead modeled in accordance with, e.g., a quadratic phase model. For each speech frame encoded with the frequency-domain coding mode, the initial phase value is taken to be the initial phase value of the immediately preceding speech frame encoded with the frequency-domain coding mode.
    Type: Grant
    Filed: February 26, 1999
    Date of Patent: October 28, 2003
    Assignee: Qualcomm Incorporated
    Inventor: Amitava Das
  • Publication number: 20020184007
    Abstract: A low-bit-rate coding technique for unvoiced segments of speech includes the steps of extracting high-time-resolution energy coefficients from a frame of speech, quantizing the energy coefficients, generating a high-time-resolution energy envelope from the quantized energy coefficients, and reconstituting a residue signal by shaping a randomly generated noise vector with quantized values of the energy envelope. The energy envelope may be generated with a linear interpolation technique. A post-processing measure may be obtained and compared with a predefined threshold to determine whether the coding algorithm is performing adequately.
    Type: Application
    Filed: July 17, 2002
    Publication date: December 5, 2002
    Inventors: Amitava Das, Sharath Manjunath
  • Patent number: 6463407
    Abstract: A low-bit-rate coding technique for unvoiced segments of speech includes the steps of extracting high-time-resolution energy coefficients from a frame of speech, quantizing the energy coefficients, generating a high-time-resolution energy envelope from the quantized energy coefficients, and reconstituting a residue signal by shaping a randomly generated noise vector with quantized values of the energy envelope. The energy envelope may be generated with linear interpolation technique. A post-processing measure may be obtained and compared with a predefined threshold to determine whether the coding algorithm is performing adequately.
    Type: Grant
    Filed: November 13, 1998
    Date of Patent: October 8, 2002
    Assignee: Qualcomm Inc.
    Inventors: Amitava Das, Sharath Manjunath
  • Patent number: 6449592
    Abstract: A method for tracking the phase of a quasi-periodic signal includes the steps of estimating the phase of the signal for frames during which the signal is periodic, monitoring the performance of the estimated phase with a closed-loop performance measure, and measuring the phase of the signal for frames during which the signal is periodic and performance of the estimated phase falls below a predefined threshold level. In estimating the phase, the initial phase value is set equal to the estimated final phase value of the previous frame if the previous frame was periodic. The initial phase value is set equal to a measured phase value of the previous frame if the previous frame was nonperiodic, or if the previous frame was periodic and performance of the estimated phase for the previous frame fell below the predefined threshold level. For frames during which the signal is nonperiodic, the phase of the signal is measured.
    Type: Grant
    Filed: February 26, 1999
    Date of Patent: September 10, 2002
    Assignee: Qualcomm Incorporated
    Inventor: Amitava Das
  • Patent number: 6260017
    Abstract: A multipulse interpolative coder for transition speech frames includes an extractor configured to represent a first frame of transitional speech samples by a subset of the samples of the frame. The coder also includes an interpolator configured to interpolate the subset of samples and a subset of samples extracted from an earlier-received frame to synthesize other samples of the first frame that are not included in the subset. The subset of samples is further simplified by selecting a set of pulses from the subset and assigning zero values to unselected pulses. In the alternative, a portion of the unselected pulses may be quantized. The set of pulses may be the pulses having the greatest absolute amplitudes in the subset. In the alternative, the set of pulses may be the most perceptually significant pulses of the subset.
    Type: Grant
    Filed: May 7, 1999
    Date of Patent: July 10, 2001
    Assignee: Qualcomm Inc.
    Inventors: Amitava Das, Sharath Manjunath
  • Patent number: 5890110
    Abstract: A variable dimension vector quantization method that uses a single "universal" codebook. The method can be given the interpretation of sampling full-dimensioned codevectors in the universal codebook and generating subcodevectors of the same dimension as input data subvector, which dimension may vary in time. A subcodevector is selected from the codebook to have minimum distortion between it and the input data subvector. The subcodevector with minimum distortion corresponds to the representative, full-dimensioned codevector in the codebook. The codebook is designed by inverse sampling of training subvectors to obtain full-dimension vectors, then iteratively clustering the training set until a stable centroid vector is obtained.
    Type: Grant
    Filed: March 27, 1995
    Date of Patent: March 30, 1999
    Assignee: The Regents of the University of California
    Inventors: Allen Gersho, Amitava Das, Ajit Venkat Rao