Time warp activation signal provider, audio signal encoder, method for providing a time warp activation signal, method for encoding an audio signal and computer programs

• US 9,431,026 B2
• Filed: 11/11/2014
• Issued: 08/30/2016
• Est. Priority Date: 07/11/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Bayer, Stefan, Disch, Sascha, Geiger, Ralf, Fuchs, Guillaume, Neuendorf, Max, Schuller, Gerald, Edler, Bernd
• Primary Examiner(s): PULLIAS, JESSE SCOTT
• Application Number:
  US14/538,735
• Publication Number:
  US 20150066488A1
• Time in Patent Office: 658 Days
• Field of Search: 704200-232, 704500-504
• US Class Current: 1/1
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/025 Detection of transients or attacks for time/frequency resolution switching
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/04 Time compression or expansion
• CPC Class Codes: G10L 21/043 by changing speed
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

Abstract

An audio encoder has a window function controller, a windower, a time warper with a final quality check functionality, a time/frequency converter, a TNS stage or a quantizer encoder, the window function controller, the time warper, the TNS stage or an additional noise filling analyzer are controlled by signal analysis results obtained by a time warp analyzer or a signal classifier. Furthermore, a decoder applies a noise filling operation using a manipulated noise filling estimate depending on a harmonic or speech characteristic of the audio signal.

Claims

1. Audio encoder for generating an encoded audio signal, comprising:

an audio signal analyzer for analyzing, whether a time frame of the audio signal comprises a harmonic or speech characteristic;

a window function controller for selecting a window function depending on a harmonic or speech characteristic of the audio signal;

a windower for windowing the audio signal using the selected window function to acquire a windowed frame; and

a processor for further processing the windowed frame to acquire the encoded audio signal;

wherein the window function controller comprises a transient detector for detecting a transient, wherein the window function controller is configured for switching from a window function for a long block to a window function for a short block, when a transient is detected and a harmonic or speech characteristic is not found by the audio signal analyzer, and for not switching to the window function for the short block, when a transient is detected and a harmonic or speech characteristic is found by the audio signal analyzer; and

wherein the window function controller is configured for switching to a window function being longer than the window function for a short block and adapted to acquire a shorter left-sided overlap length with a previous window than the window function for a long block, when a transient is detected and the signal comprises a harmonic or speech characteristic, such that the window function adapted to acquire a shorter overlap length is used for windowing a speech onset or an onset of a harmonic signal.

2. Method for generating an encoded audio signal, comprising:

analyzing, whether a time frame of the audio signal comprises a harmonic or speech characteristic;

selecting a window function depending on a harmonic or speech characteristic of the audio signal;

windowing the audio signal using the selected window function to acquire a windowed frame; and

processing the windowed frame to acquire the encoded audio signal;

wherein a switching is performed from a window function for a long block to a window function for a short block, when a transient is detected and a harmonic or speech characteristic is not found by the analyzing, and

wherein a switching is performed to a window function being longer than the window function for a short block and comprising a shorter left-sided overlap than the window function for a long block, when a transient is detected and the signal comprises a harmonic or speech characteristic, such that the window function comprising a shorter overlap is used for windowing a speech onset or an onset of a harmonic signal.

3. A non-transitory computer readable medium having stored thereon a computer program comprising a program code for performing, when running on a computer, the method of claim 2.