Audio enhancement in coded domain

An apparatus, comprising:

• a parameter value determiner configured to determine an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain and determine an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain, wherein a coded audio signal comprises indices that represent audio signal parameters comprising at least the fixed codebook gain representing a first characteristic of the audio signal and the adaptive codebook gain;
• an adjuster configured to adjust the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• and
• an index value determiner configured to determine a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value.

A method, comprising:

• determining, at an apparatus, an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain, wherein a coded audio signal comprises indices that represent audio signal parameters comprising at least the fixed codebook gain representing a first characteristic of the audio signal, an adaptive codebook gain and a background noise parameter;
• adjusting the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• determining an old adaptive codebook gain value gp—old from the index further corresponding to the adaptive codebook gain;
• determining a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value;
• detecting a current background noise parameter index value;
• and
• determining a new background noise parameter index value corresponding to the enhanced first characteristic.

An apparatus, comprising:

• parameter value determination means for determining an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain and for determining an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain, wherein a coded audio signal comprises indices that represent audio signal parameters comprising at least the fixed codebook gain representing a first characteristic of the audio signal, the adaptive codebook gain and a background noise parameter;
• adjusting means for adjusting the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• index value determination means for determining a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| flew between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value;
• detecting means for detecting a current background noise parameter index value;
• and
• determining means for determining a new background noise parameter index value corresponding to the enhanced first characteristic.

A computer program embodied on a computer-readable medium comprising a program code configured to control a processor to execute a process of enhancing a coded audio signal comprising indices which represent audio signal parameters which comprise at least a fixed codebook gain representing a first characteristic of the audio signal and an adaptive codebook gain, the process comprising:

• determining an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain;
• adjusting the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• determining an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain;
• and
• determining a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values, by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value.

A computer program embodied on a computer-readable medium comprising a program code configured to control a processor to execute a process of enhancing a coded audio signal comprising indices which represent audio signal parameters which comprise at least a fixed codebook gain representing a first characteristic of the audio signal, an adaptive codebook gain and a background noise parameter, the process comprising:

• determining an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain;
• adjusting the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• determining an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain;
• determining a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value;
• detecting a current background noise parameter index value;
• and
• determining a new background noise parameter index value corresponding to the enhanced first characteristic.

An apparatus, comprising:

• parameter value determination means for determining an old fixed codebook gain correction factor gp—old from an index corresponding to a fixed codebook gain and determining an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain, wherein a coded audio signal comprises indices that represent audio signal parameters comprising at least the fixed codebook gain representing a first characteristic of the audio signal and the adaptive codebook gain;
• adjusting means for adjusting the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• and
• index value determination means for determining a new index value from a table relating index values to fixed codebook gain correction values and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value.

An apparatus, comprising:

• a parameter value determiner configured to determine an old fixed codebook gain correction factor {circumflex over (γ)}gcold from an index corresponding to a fixed codebook gain and determine an old adaptive codebook gain value gp—old from the index further corresponding to an adaptive codebook gain, wherein a coded audio signal comprises indices that represent audio signal parameters comprising at least the fixed codebook gain representing a first characteristic of the audio signal, the adaptive codebook gain and a background noise parameter;
• an adjuster configured to adjust the old fixed codebook gain correction factor in order to achieve an enhanced first characteristic, thereby obtaining a desired gain β·{circumflex over (γ)}gcold;
• an index value determiner configured to determine a new index value from a table relating index values to fixed codebook gain correction factors and relating the index values to adaptive codebook gain values by minimizing an error |β·{circumflex over (γ)}gcold−{circumflex over (γ)}gcnew| between the desired gain and a new fixed codebook gain correction factor {circumflex over (γ)}gcnew corresponding to the new index value such that no audible error is introduced to a new adaptive codebook gain value gp—new corresponding to the new index value;
• a detector configured to detect a current background noise parameter index value;
• and
• a determiner configured to determine a new background noise parameter index value corresponding to the enhanced first characteristic.