Companding system and method to reduce quantization noise using advanced spectral extension

An apparatus for processing an audio signal comprising:

• a first interface for receiving a compressed audio signal that includes a plurality of segments;
• and
• an expander expanding the compressed audio signal including determining a respective gain for each segment of a plurality of segments, wherein the gain is in the frequency domain and is based on a p-norm of spectral magnitudes of each segment of the plurality of segments of frequency domain samples of the initial audio signal,
• wherein the p-norm value is selected to emphasize weak spectral content of the audio signal versus strong spectral content of the audio signal, and applying the respective gain to each segment of the plurality of segments to amplify segments of relatively high intensity and attenuate segments of relatively low intensity,
• wherein each respective gain for each time segment is calculated using subband samples in a subset of subbands in each respective time segment.

A method of compressing an audio signal comprising multiple channels, the method comprising:

• receiving a time-frequency tiled representation of the audio signal, wherein the time-frequency tiled representation of the audio signal comprises a division of the audio signal into time slots, wherein each time slot is divided into frequency subbands;
• and
• compressing the time-frequency tiled representation of the audio signal to reduce a dynamic range of the audio signal;
• wherein compressing the time-frequency tiled representation of the audio signal comprises:
• dividing channels of the audio signal into discrete subsets of channels based on grouping information;
• and
• for each discrete subset of channels:
• calculating a shared gain for a time slot of the time-frequency tiled representation of the audio signal, wherein calculating the shared gain includes reducing a compression level in response to control information;
• and
• applying the shared gain for the time slot to each frequency subband of each channel of the discrete subset of channels.

A apparatus for compressing an audio signal comprising multiple channels, the apparatus comprising:

• a first interface receiving a time-frequency tiled representation of the audio signal, wherein the time-frequency tiled representation of the audio signal comprises a division of the audio signal into time slots, wherein each time slot is divided into frequency subbands;
• and
• a compressor compressing the time-frequency tiled representation of the audio signal to reduce a dynamic range of the audio signal;
• wherein compressing the time-frequency tiled representation of the audio signal comprises:
• dividing channels of the audio signal into discrete subsets of channels based on grouping information;
• and
• for each discrete subset of channels:
• calculating a shared gain for a time slot of the time-frequency tiled representation of the audio signal, wherein calculating the shared gain includes reducing a compression level in response to control information;
• and
• applying the shared gain for the time slot to each frequency subband of each channel of the discrete subset of channels.