Sub-band codec with native voice activity detection

A method for decoding an encoded frame of an audio signal, comprising:

• receiving a bit stream representative of the encoded frame;
• determining if the encoded frame is a voice frame or a noise frame;
• and
• responsive to determining that the encoded frame is a noise frame,
• extracting one or more indices from the bit stream, wherein each index is associated with a corresponding frequency sub-band within a plurality of frequency sub-bands;
• for each index, reading a previously-processed series of sub-band samples associated with the frequency sub-band with which the index is associated from a history buffer wherein the index identifies the location of the previously processed series of sub-band samples in the history buffer;
• generating a series of decoded output audio samples based on the previously-processed series of sub-band samples read from the history buffer.

An audio encoder, comprising:

• an analysis filter bank configured to receive a series of input audio samples representative of a frame of an audio signal and to generate a series of sub-band samples for each of a plurality of frequency sub-bands based on the input audio samples;
• scale factor determination logic configured to determine a scale factor for each frequency sub-band based on the sub-band samples generated for each frequency sub-band;
• a voice activity detector configured to determine if the frame is a voice frame or a noise frame based on one or more of the scale factors;
• and
• sub-band index determination logic configured to identify and encode an index representative of a previously-processed series of sub-band samples stored in a history buffer for at least one of the frequency sub-bands responsive to a determination that the frame is a noise frame;
• and
• bit packing logic configured to receive the encoded index and arrange the encoded index within a bit stream for transmission to a decoder.

An audio decoder, comprising:

• bit unpacking logic configured to receive a bit stream representative of an encoded frame of an audio signal;
• a noise frame detector configured to determine if the encoded frame is a voice frame or a noise frame;
• a sub-band index reader configured to extract one or more indices from the bit stream responsive to a determination that the encoded frame is a noise frame, wherein each index is associated with a corresponding frequency sub-band within a plurality of frequency sub-bands;
• a sub-band samples reader configured to read, for each index, a previously-processed series of sub-band samples associated with the frequency sub-band with which the index is associated from a history buffer responsive to a determination that the encoded frame is a noise frame, wherein the index identifies the location of the previously processed series of sub-band samples in the history buffer;
• and
• a synthesis filter bank configured to generate a series of decoded output audio samples based on the previously-processed series of sub-band samples read from the history buffer responsive to a determination that the encoded frame is a noise frame.