# US 11,443,751 B2 · Phase reconstruction in a speech decoder > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,443,751 B2 - Document ID: US11443751B2 - Status: Granted - Kind: B2 - Application number: 17/175,455 - Filed: 2021-02-12 - Published: 2021-06-03 - Granted: 2022-09-13 - Earliest claimed: 2018-12-17 - Assignees: Microsoft Technology Licensing, LLC - Applicants: Microsoft Technology Licensing, LLC - Inventors: Soren Skak Jensen; Sriram Srinivasan; Koen Bernard Vos - Web page: https://patentgrep.com/patent/US11443751B2 ## CPC - G10L 19/0018: {Speech coding using phonetic or linguistical decoding of the source; Reconstruction using text-to-speech synthesis} - G10L 19/08: Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters - G10L 19/265: {Pre-filtering, e.g. high frequency emphasis prior to encoding} - G10L 21/038: using band spreading techniques - G10L 25/12: the extracted parameters being prediction coefficients - G10L 25/69: for evaluating synthetic or decoded voice signals - G10L 25/72: for transmitting results of analysis - G10L 19/0212: {using orthogonal transformation} - G10L 19/125: Pitch excitation, e.g. pitch synchronous innovation CELP [PSI-CELP] - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract Innovations in phase quantization during speech encoding and phase reconstruction during speech decoding are described. For example, to encode a set of phase values, a speech encoder omits higher-frequency phase values and/or represents at least some of the phase values as a weighted sum of basis functions. Or, as another example, to decode a set of phase values, a speech decoder reconstructs at least some of the phase values using a weighted sum of basis functions and/or reconstructs lower-frequency phase values then uses at least some of the lower-frequency phase values to synthesize higher-frequency phase values. In many cases, the innovations improve the performance of a speech codec in low bitrate scenarios, even when encoded data is delivered over a network that suffers from insufficient bandwidth or transmission quality problems. ## Claims ### Claim 1 A computer system comprising: an input buffer, implemented in memory of the computer system, configured to receive encoded data as part of a bitstream; a speech decoder, implemented using one or more processors of the computer system, configured to decode the encoded data to reconstruct speech by performing operations comprising: decoding residual values, including: decoding a set of phase values, including reconstructing at least some of the set of phase values using a weighted sum of basis functions; and reconstructing the residual values based at least in part on the set of phase values; and filtering the residual values according to linear prediction coefficients; and an output buffer configured to store the reconstructed speech for output. ### Claim 2 (depends on 1) The computer system of claim 1, wherein the reconstructing the residual values includes: repeating the set of phase values for one or more subframes of a current frame; based at least in part on the repeated sets of phase values for the respective subframes, reconstructing complex amplitude values for the respective subframes; and applying an inverse frequency transform to the complex amplitude values for the respective subframes. ### Claim 3 (depends on 1) The computer system of claim 1, wherein the reconstructed phase values are lower-frequency phase values of the set of phase values, and wherein the decoding the set of phase values further includes using at least some of the lower-frequency phase values to synthesize higher-frequency phase values of the set of phase values, each of the higher-frequency phase values having a frequency above a cutoff frequency. ### Claim 4 (depends on 3) The computer system of claim 3, wherein the decoding the set of phase values further includes determining the cutoff frequency based at least in part on a target bitrate for the encoded data and/or pitch cycle information. ### Claim 5 (depends on 1) The computer system of claim 1, wherein the basis functions are sine functions. ### Claim 6 (depends on 1) The computer system of claim 1, wherein the decoding the set of phase values further includes: decoding a set of coefficients that weight the basis functions; decoding an offset value and a slope value that parameterize a linear component; and using the set of coefficients, the offset value, and the slope value as part of the reconstructing the at least some of the set of phase values. ### Claim 7 (depends on 6) The computer system of claim 6, wherein the decoding the set of phase values further includes determining a count of the coefficients that weight the basis functions. ### Claim 8 (depends on 1) The computer system of claim 1, wherein the reconstructing the residual values includes: based at least in part on the set of phase values, reconstructing complex amplitude values for one or more subframes; adaptively smoothing the complex amplitude values for the respective subframes based at least in part on one or more of pitch cycle information and differences in amplitude values across boundaries; applying an inverse frequency transform to the smoothed complex amplitude values for the respective subframes; and selectively adding noise to the residual values based at least in part on correlation values and a sparseness value. ### Claim 9 In a computer system that implements a speech decoder, a method comprising: receiving encoded data as part of a bitstream; decoding the encoded data to reconstruct speech, including: decoding residual values, including: decoding a sparseness value and correlation values; decoding one or more sets of magnitude values; decoding a set of phase values; and reconstructing the residual values, including: reconstructing complex amplitude values for one or more subframes of a current frame using the one or more sets of magnitude values and the set of phase values; applying an inverse frequency transform to the complex amplitude values for the respective subframes; and selectively adding noise to the residual values based at least in part on the correlation values and the sparseness value; and filtering the residual values according to linear prediction coefficients; and storing the reconstructed speech for output. ### Claim 10 (depends on 9) The method of claim 9 wherein the reconstructing the residual values further includes adaptively smoothing the complex amplitude values for the respective subframes based at least in part on one or more of pitch cycle information and differences in amplitude values across boundaries, and wherein the inverse frequency transform is applied to the smoothed complex amplitude values. ### Claim 11 (depends on 9) The method of claim 9, wherein the reconstructing the residual values further includes repeating the set of phase values for at least one of the one or more subframes, wherein the complex amplitude values for the respective subframes are reconstructed using the repeated sets of phase values. ### Claim 12 (depends on 9) The method of claim 9, wherein the decoding the set of phase values includes using at least some lower-frequency phase values to synthesize higher-frequency phase values of the set of phase values, each of the higher-frequency phase values having a frequency above a cutoff frequency. ### Claim 13 (depends on 12) The method of claim 12, wherein the decoding the set of phase values further includes determining the cutoff frequency based at least in part on a target bitrate for the encoded data and/or pitch cycle information. ### Claim 14 (depends on 9) The method of claim 9, wherein the decoding the set of phase values includes reconstructing at least some of the set of phase values using a weighted sum of basis functions. ### Claim 15 (depends on 14) The method of claim 14, wherein the decoding the set of phase values further includes: decoding a set of coefficients that weight the basis functions; decoding an offset value and a slope value that parameterize a linear component; and using the set of coefficients, the offset value, and the slope value as part of the reconstructing the at least some of the set of phase values. ### Claim 16 One or more computer-readable memory or storage devices having stored thereon encoded data as part of a bitstream, the encoded data including a set of coefficients, an offset value, and a slope value for a set of phase values, the encoded data being organized to facilitate decoding of the encoded data to reconstruct speech, with a speech decoder implemented using one or more processors, by operations comprising: decoding residual values, including: decoding the set of phase values using the set of coefficients, the offset value, and the slope value, including reconstructing at least some of the set of phase values using a weighted sum of basis functions; and reconstructing the residual values based at least in part on the set of phase values; and filtering the residual values according to linear prediction coefficients. ### Claim 17 (depends on 16) The one or more computer-readable memory or storage devices of claim 16, wherein the offset value and the slope value parameterize a linear component, and wherein the reconstructing the at least some of the set of phase values also uses the linear component. ### Claim 18 (depends on 16) The one or more computer-readable memory or storage devices of claim 16, wherein the encoded data further includes a target bitrate for the encoded data and/or pitch cycle information, wherein the reconstructed phase values are lower-frequency phase values of the set of phase values, and wherein the decoding the set of phase values further includes: determining a cutoff frequency based at least in part on the target bitrate for the encoded data and/or the pitch cycle information; and using at least some of the lower-frequency phase values to synthesize higher-frequency phase values of the set of phase values, each of the higher-frequency phase values having a frequency above the cutoff frequency. ### Claim 19 (depends on 16) The one or more computer-readable memory or storage devices of claim 16, wherein the encoded data further includes encoded data for one or more sets of magnitude values, and wherein the decoding the set of phase values further includes: decoding the one or more sets of magnitude values; and reconstructing complex amplitude values based at least in part on the one or more sets of magnitude values and the set of phase values. ### Claim 20 (depends on 16) The one or more computer-readable memory or storage devices of claim 16, wherein the encoded data further includes a sparseness value and correlation values, and wherein the operations further comprise: decoding the sparseness value and the correlation values; and selectively adding noise to the residual values based at least in part on the correlation values and the sparseness value.