Spectrum Flatness Control for Bandwidth Extension
First Claim
1. A method of decoding an encoded audio bitstream at a decoder, the method comprising:
- receiving the audio bitstream, the audio bitstream comprising a low band bitstream;
decoding the low band bitstream to get low band coefficients in a frequency domain;
copying a plurality of the low band coefficients to a high frequency band location to generate high band coefficients;
processing the high band coefficients to form processed high band coefficients, processing comprisingmodifying an energy envelope of the high band coefficients, modifying comprising multiplying modification gains to flatten or smooth the high band coefficients, andapplying a received spectral envelope to the high band coefficients, the received spectral envelope being decoded from the received audio bitstream; and
inverse-transforming the low band coefficients and the processed high band coefficients to a time domain to obtain a time domain output signal.
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Abstract
In accordance with an embodiment, a method of decoding an encoded audio bitstream at a decoder includes receiving the audio bitstream, decoding a low band bitstream of the audio bitstream to get low band coefficients in a frequency domain, and copying a plurality of the low band coefficients to a high frequency band location to generate high band coefficients. The method further includes processing the high band coefficients to form processed high band coefficients. Processing includes modifying an energy envelope of the high band coefficients by multiplying modification gains to flatten or smooth the high band coefficients, and applying a received spectral envelope decoded from the received audio bitstream to the high band coefficients. The low band coefficients and the processed high band coefficients are then inverse-transformed to the time domain to obtain a time domain output signal.
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Citations
24 Claims
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1. A method of decoding an encoded audio bitstream at a decoder, the method comprising:
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receiving the audio bitstream, the audio bitstream comprising a low band bitstream; decoding the low band bitstream to get low band coefficients in a frequency domain; copying a plurality of the low band coefficients to a high frequency band location to generate high band coefficients; processing the high band coefficients to form processed high band coefficients, processing comprising modifying an energy envelope of the high band coefficients, modifying comprising multiplying modification gains to flatten or smooth the high band coefficients, and applying a received spectral envelope to the high band coefficients, the received spectral envelope being decoded from the received audio bitstream; and inverse-transforming the low band coefficients and the processed high band coefficients to a time domain to obtain a time domain output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A post-processing method of generating a decoded speech/audio signal at a decoder and improving spectrum flatness of a generated high frequency band, the method comprising:
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generating high band coefficients from low band coefficients in a frequency domain using a BandWidth Extension (BWE) high band coefficient generation method; flattening or smoothing an energy envelope of the high band coefficients by multiplying flattening or smoothing gains to the high band coefficients; shaping and determining energies of the high band coefficients by using a BWE shaping and determining method; and inverse-transforming the low band coefficients and the high band coefficients to a time domain to obtain a time domain output speech/audio signal. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A system for receiving an encoded audio signal, the system comprising:
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a low-band block configured to transform a low band portion of the encoded audio signal into frequency domain low band coefficients at an output of the low-band block; a high-band block coupled to the output of the low-band block, the high band block configured to generate high band coefficients at an output of the high band block by copying a plurality of the low band coefficients to a high frequency band locations; an envelope shaping block coupled to the output of the high-band block, the envelope shaping block configured to produce shaped high band coefficients at an output of the envelope shaping block, wherein the envelope shaping block configured to modify an energy envelope of the high band coefficients by multiplying modification gains to flatten or smooth the high band coefficients, and apply a received spectral envelope to the high band coefficients, the received spectral envelope being decoded from the encoded audio signal; and an inverse transform block coupled to the output of envelope shaping block and to the output of the low band block, the inverse transform block configured to produce a time domain audio output signal. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A non-transitory computer readable medium has an executable program stored thereon, wherein the program instructs a processor to perform the steps of:
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decoding an encoded audio signal to produce a decoded audio signal, wherein the encoded audio signal includes a coded representation of an input audio signal; and postprocessing the decoded audio signal with a spectrum flatness control for spectrum bandwidth extension. - View Dependent Claims (24)
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Specification