# US 10,311,883 B2 · Transient detection with hangover indicator for encoding an audio signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,311,883 B2 - Document ID: US10311883B2 - Status: Granted - Kind: B2 - Application number: 15/296,600 - Filed: 2016-10-18 - Published: 2017-02-09 - Granted: 2019-06-04 - Earliest claimed: 2007-08-27 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Anisse Taleb; Gustaf Ullberg - Web page: https://patentgrep.com/patent/US10311883B2 ## CPC - G10L 19/025: Detection of transients or attacks for time/frequency resolution switching - G10L 19/0212: {using orthogonal transformation} - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract A transient detector (100) analyzes (110) a given frame n of the input audio signal to determine, based on audio signal characteristics of the given frame n, a transient hangover indicator for a following frame n+1, and signals (120) the determined transient hangover indicator to an associated audio encoder (10) to enable proper encoding of the following frame n+1. ## Claims ### Claim 1 An audio encoder apparatus comprising transient detector circuitry operating on an audio signal, wherein said transient detector circuitry is configured to: analyze a given frame n of said audio signal to determine whether a transient is present in frame n of the audio signal, wherein frame n of the audio signal comprises at least a first block and a second block, and frame n of the audio signal is immediately followed by frame n+1 of the audio signal; and set an istransient flag for frame n+1 to a logical value of TRUE as a result of determining that frame n is a transient frame, to enable proper encoding of said following frame n+1, wherein the audio encoder is configured to determine whether frame n of the audio signal is a transient frame by performing a transient detector process comprising: calculating a short term energy value for the first block of frame n (EST(1)), calculating a long term energy value for the first block of frame n (ELT(1)), and determining whether EST (1)/ELT(1) is greater than or equal to a threshold (ρ), and the audio encoder is configured such that the audio encoder determines that a transient is not present in frame n of the audio signal as a result of determining that EST (1)/ELT(1) is less than ρ, wherein the audio encoder apparatus is further configured to: determine whether the frame n of the audio signal is a transient frame in dependence on a predetermined window function; scale said given frame n by said window function to produce a first scaled frame; determine a transient indicator for said given frame n based on the first scaled frame; scale said given frame n by said window function shifted one frame forward in time to produce a second scaled frame; and determine a transient hangover indicator for said following frame n+1 based on the second scaled frame. ### Claim 2 An audio encoding method, the method comprising: analyzing a given frame n of an audio signal comprising a plurality of frames including frame n and a frame n+1, wherein frame n of the audio signal comprises at least a first block and a second block, and frame n of the audio signal is immediately followed by frame n+1 of the audio signal, to determine whether a transient hangover condition is satisfied for frame n+1; and triggering a transient for frame n+1 as a result of determining that the transient hangover condition for frame n+1 is satisfied, thereby enabling proper encoding of frame n+1, wherein determining that the transient hangover condition is satisfied comprises determining whether a transient is present in frame n of the audio signal, determining whether a transient is present in frame n of the audio signal comprises performing a transient detector process comprising: i) calculating a short term energy value for the first block of frame n (E(1)), ii) calculating a long term energy value for the first block of frame n (ELT(1)), and iii) determining whether a ratio of E(1) to ELT(1) satisfies a first condition, and a transient is determined not to be present in frame n of the audio signal as a result of determining that the ratio of E(1) to ELT(1) does not satisfy the first condition. ### Claim 3 (depends on 2) The method of claim 2, wherein determining whether the transient hangover condition is satisfied in comprises determining whether audio signal characteristics representative of a transient in said given frame n is not suppressed after a windowing operation based on a window function. ### Claim 4 (depends on 3) The method of claim 3, wherein said window function corresponds to a window function used for transform coding of frame n of said audio signal in said audio encoder apparatus, but shifted one frame forward in time. ### Claim 5 (depends on 4) The method of claim 4, further comprising encoding the audio signal using a lapped transform. ### Claim 6 (depends on 3) The method of claim 3, further comprising: scaling said given frame n by said window function to produce a first scaled frame; determining a transient indicator for said given frame n based on the first scaled frame; scaling said given frame n by said window function shifted one frame forward in time to produce a second scaled frame; and determining a transient hangover indicator for said following frame n+1 based on the second scaled frame. ### Claim 7 (depends on 2) The method of claim 2, wherein determining that the transient hangover condition is satisfied further comprises determining a location of the transient in said given frame n. ### Claim 8 (depends on 7) The method of claim 7, wherein determining that the transient hangover condition is satisfied further comprises determining that the transient in said given frame n is located at the center or end of frame n. ### Claim 9 (depends on 8) The method of claim 8, wherein determining that the transient hangover condition is satisfied further comprises determining whether a transient that is present in frame n is located at the beginning of frame n. ### Claim 10 (depends on 2) The method of claim 2, further comprising encoding frame n+1 based on the triggering of the transient for frame n+1.