Method and apparatus for generating an enhancement layer within an audio coding system
View Patent ↗During operation an input signal to be coded is received and coded to produce a coded audio signal. The coded audio signal is then scaled with a plurality of gain values to produce a plurality of scaled coded audio signals, each having an associated gain value and a plurality of error values are determined existing between the input signal and each of the plurality of scaled coded audio signals. A gain value is then chosen that is associated with a scaled coded audio signal resulting in a low error value existing between the input signal and the scaled coded audio signal. Finally, the low error value is transmitted along with the gain value as part of an enhancement layer to the coded audio signal.
1. A method for an embedded audio encoder to embed coding of a signal, comprising the steps of:
the embedded audio encoder receiving an input signal to be coded;
a first layer of the embedded audio encoder coding the input signal to produce a first layer reconstructed audio signal;
a second layer of the embedded audio encoder scaling the first layer reconstructed audio signal with a plurality of gain values to produce a plurality of scaled reconstructed audio signals, wherein the plurality of gain values are a function of the first layer reconstructed audio signal and further, wherein each of the plurality of scaled reconstructed audio signals has an associated gain value;
the second layer of the embedded audio encoder determining a plurality of error values based on the input signal and each of the plurality of scaled reconstructed audio signals;
the second layer of the audio encoder choosing a gain value from the plurality of gain values based on the plurality of error values; and
the embedded audio encoder transmitting or storing the gain value as part of an enhancement layer to a coded audio signal.
2. The method of claim 1 wherein the plurality of gain values comprise frequency selective gain values.
3. The method of claim 1 wherein the first layer of the embedded audio encoder comprises a Code Excited Linear Prediction (CELP) encoder.
4. A method for an embedded audio decoder receiving a coded audio signal and an enhancement to the coded audio signal, the method comprising the steps of:
a first layer of the embedded audio decoder receiving the coded audio signal; and
a second layer of the audio decoder receiving the enhancement to the coded audio signal, wherein the enhancement to the coded audio signal comprises a gain value and an error signal associated with the gain value, wherein the gain value was chosen by a transmitter from a plurality of gain values, wherein the gain value is associated with a scaled reconstructed audio signal resulting in a particular error value existing between an audio signal and the scaled reconstructed audio signal; and
the audio decoder enhancing the coded audio signal based on the gain value and the error value.
5. The method of claim 4 wherein the gain value comprises a frequency selective gain value.
6. The method of claim 5 wherein the frequency selective gain values
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where generally 0≦γ j (k)≦1 and g j (k) is the gain of a k-th position of a j-th candidate vector.
7. A method of claim 5 wherein the first layer of the embedded audio decoder comprises a Code Excited Linear Prediction (CELP) decoder.
8. A method of claim 5 wherein the embedded decoder comprises a third layer wherein the third layer is between the first layer and the second layer, and wherein the third layer outputs a frequency domain error vector.
9. An apparatus comprising:
an embedded encoder receiving an input signal to be coded, wherein the embedded encoder comprises:
a first layer of the embedded audio encoder coding the input signal to produce a first layer reconstructed audio signal;
a second layer of the embedded encoder scaling the first layer reconstructed audio signal with a plurality of gain values to produce a plurality of scaled reconstructed audio signals, wherein the plurality of gain values are a function of the first layer reconstructed audio signal and further, wherein each of the plurality of scaled reconstructed audio signals has an associated gain value,
wherein the second layer of the embedded encoder determines a plurality of error values existing between the input signal and each of the plurality of scaled reconstructed audio signals, wherein
the second layer of the embedded encoder choosing a gain value from the plurality of gain values, and further, wherein the gain value is chosen based on the plurality of error values existing between the input signal and the scaled reconstructed audio signal; and
a transmitter transmitting the selected gain value as part of an enhancement layer to a coded audio signal.
10. The apparatus of claim 9 wherein the plurality of gain values comprise frequency selective gain values.
11. The apparatus of claim 10 wherein the frequency selective gain values
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otherwise
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where generally 0≦γ j (k)≦1 and g j (k) is the gain of a k-th position of a j-th candidate vector.
12. An apparatus comprising:
a first layer of an embedded decoder receiving a coded audio signal; and
a second layer of the embedded layer decoder receiving enhancement to the coded audio signal and producing an enhanced audio signal, wherein the enhancement to the coded audio signal comprises a gain value and an error signal associated with the gain value, wherein the gain value was chosen by an encoder from a plurality of gain values, wherein the gain value is associated with a scaled reconstructed audio signal resulting in a particular error value existing between an input audio signal and the scaled reconstructed audio signal.
13. An apparatus comprising:
a first layer of an embedded decoder receiving codewords to produce a reconstructed audio signal; and
a second layer of the embedded decoder receiving codewords for enhancement to the coded audio signal and outputting an enhanced reconstructed audio signal, wherein the enhancement to the reconstructed audio signal comprises a frequency selective gain value and an error signal associated with the gain value, wherein the frequency selective gain value is based on the reconstructed audio signal.
14. The method of claim 13 wherein the frequency domain comprises the MDCT domain.
15. The method of claim 13 wherein the step of receiving the enhancement further comprises:
receiving a gain codeword i g ; and
generating the frequency selective gain vector based on the gain codeword and the first error value.
16. The method of claim 13 wherein the frequency selective gain value comprises g j (k), wherein g j (k) is the gain of a k-th frequency component of a j-th candidate vector.
17. A method of claim 13 where in the frequency selective gain is based on the frequency domain error vector Ê 3 .