Conversion of synthesized spectral components for encoding and low-complexity transcoding

A method of transcoding encoded audio information comprising:

• receiving a first encoded signal conveying first quantized scaled values and first scale factors representing spectral components of an audio signal, wherein each first scale factor is associated with one or more first quantized scaled values, each first quantized scaled value is scaled according to its associated first scale factor, and each first quantized scaled value and associated first scale factor represent a respective spectral component;
• deriving second scale factors from the first scale factors;
• allocating bits according to a first bit allocation process in response to one or more first control parameters and obtaining dequantized scaled values from the first quantized scaled values by dequantizing according to quantizing resolutions based on numbers of bits allocated by the first bit allocation process;
• allocating bits according to a second bit allocation process in response to one or more second control parameters and obtaining second quantized scaled values by quantizing the dequantized scaled values using quantizing resolutions based on numbers of bits allocated by the second bit allocation process;
• and
• assembling the second quantized scaled values, the second scale factors and one or more second control parameters into a second encoded signal.

An encoder for processing an audio signal, wherein the encoder comprises:

• means for receiving a signal conveying initial scaled values and initial scale factors representing spectral components of the audio signal, wherein each initial scale factor is associated with one or more initial scaled values, each initial scaled value is scaled according to its associated initial scale factor, and each initial scaled value and associated initial scale factor represent the value of a respective spectral component;
• means for generating coded spectral information by performing a coding process that is responsive to initial spectral information that comprises at least some of the initial scale factors;
• means for deriving one or more first control parameters in response to the initial scale factors and a first bit-rate requirement;
• means for allocating bits according to a first bit allocation process in response to the one or more first control parameters;
• means for obtaining quantized scaled values by quantizing at least some of the initial scaled values using quantizing resolutions based on numbers of bits allocated by the first bit allocation process;
• means for deriving one or more second control parameters in response to at least some of the initial scale factors, one or more modified scale factors and a second bit-rate requirement, wherein the one or more modified scale factors are obtained by:
• analyzing the initial spectral information with respect to a synthesis process to be applied to the coded spectral information in a decoding method that generates synthesized spectral components represented by synthesized scaled values and associated synthesized scale factors to identify one or more potentially unnormalized synthesized scaled values, wherein the synthesis process is quasi-inverse to the coding process, and
• generating the one or more modified scale factors to represent modified values of initial scale factors in the initial spectral information corresponding to synthesized scale factors that are associated with at least some of the one or more potentially unnormalized synthesized scaled values to compensate for loss of normalization of the identified potentially unnormalized synthesized scaled values;
• and means for assembling encoded information into an encoded signal,
• wherein the encoded information represents the quantized scaled values, at least some of the initial scale factors, the coded spectral information, the one or more first control parameters and the one or more second control parameters.

A transcoder for transcoding encoded audio information, wherein the transcoder comprises:

• means for receiving a first encoded signal conveying first quantized scaled values and first scale factors representing spectral components of an audio signal, wherein each first scale factor is associated with one or more first quantized scaled values, each first quantized scaled value is scaled according to its associated first scale factor, and each first quantized scaled value and associated first scale factor represent a respective spectral component;
• means for deriving second scale factors from the first scale factors;
• means for allocating bits according to a first bit allocation process in response to one or more first control parameters and obtaining dequantized scaled values from the first quantized scaled values by dequantizing according to quantizing resolutions based on numbers of bits allocated by the first bit allocation process;
• means for allocating bits according to a second bit allocation process in response to one or more second control parameters and obtaining second quantized scaled values by quantizing the dequantized scaled values using quantizing resolutions based on numbers of bits allocated by the second bit allocation process;
• and
• means for assembling the second quantized scaled values, the second scale factors and one or more second control parameters into a second encoded signal.

A medium conveying a program of instructions executable by a device, wherein execution of the program of instructions causes the device to perform a method for transcoding audio information, wherein the method comprises:

• receiving a signal conveying initial scaled values and initial scale factors representing spectral components of the audio signal, wherein each initial scale factor is associated with one or more initial scaled values, each initial scaled value is scaled according to its associated initial scale factor, and each initial scaled value and associated initial scale factor represent the value of a respective spectral component;
• generating coded spectral information by performing a coding process that is responsive to initial spectral information that comprises at least some of the initial scale factors;
• deriving one or more first control parameters in response to the initial scale factors and a first bit-rate requirement;
• allocating bits according to a first bit allocation process in response to the one or more first control parameters;
• obtaining quantized scaled values by quantizing at least some of the initial scaled values using quantizing resolutions based on numbers of bits allocated by the first bit allocation process;
• deriving one or more second control parameters in response to at least some of the initial scale factors, one or more modified scale factors and a second bit-rate requirement, wherein the one or more modified scale factors are obtained by:
• analyzing the initial spectral information with respect to a synthesis process to be applied to the coded spectral information in a decoding method that generates synthesized spectral components represented by synthesized scaled values and associated synthesized scale factors to identify one or more potentially unnormalized synthesized scaled values, wherein the synthesis process is quasi-inverse to the coding process, and
• generating the one or more modified scale factors to represent modified values of initial scale factors in the initial spectral information corresponding to synthesized scale factors that are associated with at least some of the one or more potentially unnormalized synthesized scaled values to compensate for loss of normalization of the identified potentially unnormalized synthesized scaled values;
• and
• assembling encoded information into an encoded signal, wherein the encoded information represents the quantized scaled values, at least some of the initial scale factors, the coded spectral information, the one or more first control parameters and the one or more second control parameters.

A medium conveying a program of instructions executable by a device, wherein execution of the program of instructions causes the device to perform a method for transcoding encoded audio information, wherein the method comprises:

• receiving a first encoded signal conveying first quantized scaled values and first scale factors representing spectral components of an audio signal, wherein each first scale factor is associated with one or more first quantized scaled values, each first quantized scaled value is scaled according to its associated first scale factor, and each first quantized scaled value and associated first scale factor represent a respective spectral component;
• deriving second scale factors from the first scale factors;
• allocating bits according to a first bit allocation process in response to one or more first control parameters and obtaining dequantized scaled values from the first quantized scaled values by dequantizing according to quantizing resolutions based on numbers of bits allocated by the first bit allocation process;
• allocating bits according to a second bit allocation process in response to one or more second control parameters and obtaining second quantized scaled values by quantizing the dequantized scaled values using quantizing resolutions based on numbers of bits allocated by the second bit allocation process;
• and
• assembling the second quantized scaled values, the second scale factors and one or more second control parameters into a second encoded signal.