# US 8,788,277 B2 · Apparatus and methods for processing a signal using a fixed-point operation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,788,277 B2 - Document ID: US8788277B2 - Status: Granted - Kind: B2 - Application number: 12/880,858 - Filed: 2010-09-13 - Published: 2011-05-19 - Granted: 2014-07-22 - Earliest claimed: 2009-09-11 - Assignees: The Trustees of Columbia University in the City of New York - Applicants: Christos Vezyrtzis; Aaron Klein; Yannis Tsividis; Daniel P. W. Ellis - Inventors: Christos Vezyrtzis; Aaron Klein; Yannis Tsividis; Daniel P. W. Ellis - Web page: https://patentgrep.com/patent/US8788277B2 ## CPC - G10L 19/0208: {Subband vocoders} - G10L 21/0364: for improving intelligibility - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract Apparatus and methods for processing compression encoded signals are provided. In some embodiments, a signal processing method is provided that includes receiving a subband of a compression encoded signal at a subband processor, generating envelope information regarding the subband of the compression encoded signal to provide changes in the dynamic range of the compression encoded signal for fixed-point digital signal processing, processing the compression encoded signal with a fixed-point companding digital signal processor using the envelope information, and producing a processed compression encoded signal at the output of the subband processor. ## Claims ### Claim 1 A digital signal processor comprising: an input configured to receive signal comprising a plurality of subbands and envelope information of the plurality of subbands, wherein the envelope information indicates a dynamic range of at least one of the plurality of subbands; a plurality of subband processors, coupled to the input, wherein each of the plurality of subband processors is configured to process a respective one of the plurality of subbands to provide a processed subband signal based on the envelope information of the one of the plurality of subbands to account for the dynamic range of the one of the plurality of subbands, wherein the one of the subband processors comprises a fixed-point signal processor configured to process the one of the plurality of subbands based on an internal state, the internal state computed based on previous values of the one of the plurality of subbands in accordance with a state-space model; and an output collector configured to provide an output signal based on the processed subband signal from each of the plurality of subband processors. ### Claim 2 (depends on 1) The digital signal processor of claim 1, wherein the one of the plurality of subband processors is configured to scale the one of the subbands using the envelope information of the one of the subbands to account for the dynamic range of the one of the plurality of subbands. ### Claim 3 (depends on 1) The digital signal processor of claim 1, wherein the envelope information comprises a scale factor indicative of the envelope information. ### Claim 4 (depends on 1) The digital signal processor of claim 1, wherein the fixed-point signal processor is further configured to process the one of the plurality of subbands based on envelope information of the internal state to account for a dynamic range of the internal state. ### Claim 5 (depends on 4) The digital signal processor of claim 4, wherein the fixed-point signal processor is configured to scale the internal state using the envelope information of the internal state to account for the dynamic range of the internal state. ### Claim 6 (depends on 4) The digital signal processor of claim 4, wherein the envelope information of the one of the plurality of subbands and the envelope information of the internal state are an integer power of 2. ### Claim 7 (depends on 4) The digital signal processor of claim 4, wherein each of the subband processors further includes an envelope generator configured to determine the envelope information of the internal state based on the envelope information of the one of the plurality of subbands, and to provide the envelope information of the internal state to the fixed-point signal processor. ### Claim 8 (depends on 7) The digital signal processor of claim 7, wherein the envelope generator is configured to determine the envelope information of the internal state by detecting changes in the envelope information of the one of the plurality of subbands. ### Claim 9 (depends on 8) The digital signal processor of claim 8, wherein if the envelope information of the one of the plurality of subbands changes by more than a pre-defined threshold, the envelope generator is configured to provide the most recent envelope information of the one of the plurality of subbands as the envelope information of the internal state. ### Claim 10 (depends on 8) The digital signal processor of claim 8, wherein if the envelope information of the one of the plurality of subbands does not change by more than a pre-defined threshold, the envelope generator is configured to provide weighted versions of past envelope information of the one of the plurality of subbands as the envelope information of the internal state. ### Claim 11 A signal processing method comprising: receiving, at an input of a digital signal processor, a signal comprising a plurality of subbands and envelope information of the plurality of subbands, wherein the envelope information indicates a dynamic range of at least one of the plurality of subbands; processing, by each of a plurality of subband processors in the digital signal processor, a respective one of the plurality of subbands to provide a processed subband signal based on the envelope information of the one of the plurality of subbands to account for the dynamic range of the one of the plurality of subbands, wherein processing the one of the plurality of subbands comprises processing the one of the plurality of subbands based on an internal state of the one of the plurality of subband processors, the internal state computed based on previous values of the one of the plurality of subbands in accordance with a state-space model; and providing, by an output collector coupled to the plurality of subband processors, an output signal based on the processed subband signal from each of the plurality of subband processors. ### Claim 12 (depends on 11) The method of claim 11, wherein the signal is an MPEG signal. ### Claim 13 (depends on 11) The method of claim 11, wherein processing the one of the plurality of subbands further comprises processing the one of the plurality of subbands based on envelope information of the internal state to account for a dynamic range of the internal state. ### Claim 14 (depends on 13) The method of claim 13, wherein the envelope information of the one of the plurality of subbands and the envelope information of the internal state are an integer power of 2. ### Claim 15 (depends on 13) The method of claim 13, further comprising determining, at an envelope generator in the one of the subband processors, the envelope information of the internal state by detecting changes in the envelope information of the one of the plurality of subbands. ### Claim 16 (depends on 15) The method of claim 15, wherein if the envelope information of the one of the plurality of subbands does not change by more than a pre-defined threshold, providing weighted versions of past envelope information of the one of the plurality of subbands as the envelope information of the internal state. ### Claim 17 A tangible, non-transitory computer readable medium including instructions operable to cause an apparatus to: receive a signal comprising a plurality of subbands and envelope information of the plurality of subbands, wherein the envelope information indicates a dynamic range of at least one of the plurality of subbands; process each of the plurality of subbands using the envelope information of the respective one of the plurality of subbands to provide a processed subband signal for the respective one of the plurality of subbands, wherein processing each of the plurality of subbands comprises processing the one of the plurality of subbands based on an internal state of the one of a plurality of subband processors, the internal state computed based on previous values of the one of the plurality of subbands in accordance with a state-space model; and provide an output signal by combining processed subband signals of the plurality of subbands. ### Claim 18 (depends on 17) The tangible, non-transitory computer readable medium of claim 17, wherein the envelope information comprises a scale factor indicative of the envelope information. ### Claim 19 (depends on 17) The tangible, non-transitory computer readable medium of claim 17, wherein the instructions are further operable to cause the apparatus to scale the internal state using envelope information of the internal state to account for the dynamic range of the internal state. ### Claim 20 (depends on 19) The tangible, non-transitory computer readable medium of claim 19, wherein instructions are further operable to cause an apparatus to determine the envelope information of the internal state by detecting changes in the envelope information of the one of the plurality of subbands.