Processing Audio Signals with Adaptive Time or Frequency Resolution

Abstract

In one aspect, a method for processing an encoded audio signal is disclosed. The method includes decoding the encoded audio signal to obtain a time-domain audio signal and then analyzing the time-domain audio signal with an analysis filter bank to obtain a plurality of complex-valued subband samples in a first frequency region. The method further includes processing the audio signal by generating a plurality of subband samples in a second frequency region based at least in part on the complex-valued subband samples in the first frequency region, grouping at least some of the plurality of subband samples in the second frequency region with an adaptive time resolution and an adaptive frequency resolution to obtain an adaptive grouping, and determining a spectral profile of at least some of the subband samples in the second frequency region based at least in part on the adaptive grouping.

1 . A method for processing an encoded audio signal, the method comprising:
 decoding the encoded audio signal to obtain a time-domain audio signal, the encoded audio signal including spectral components from at least two channels of audio content;   analyzing the time-domain audio signal to obtain a plurality of complex-valued subband samples in a first frequency region for each of the at least two channels of audio content; and   processing each of the at least two channels of audio content by:
 generating a plurality of subband samples in a second frequency region based at least in part on the complex-valued subband samples in the first frequency region, 
 grouping at least some of the plurality of subband samples in the second frequency region with an adaptive time resolution and an adaptive frequency resolution to obtain an adaptive grouping, and 
 determining a spectral profile of at least some of the subband samples in the second frequency region based at least in part on the adaptive grouping; 
   wherein the method is performed with one or more computing devices, a parameter in the encoded audio signal indicates the adaptive frequency resolution for each of the at least two channels of audio content by specifying either a first frequency resolution or a second frequency resolution for each of the at least two channels of audio content, and the first frequency resolution is finer than the second frequency resolution.   
     
     
         2 . The method of  claim 1  wherein the adaptive grouping is signaled in the encoded audio signal as one or more parameters. 
     
     
         3 . The method of  claim 2  wherein the one or more parameters are used to determine a start time border and an end time border of a time segment. 
     
     
         4 . The method of  claim 3  wherein an end time border of a first time segment is a start time border of a second time segment. 
     
     
         5 . The method of  claim 1  wherein the spectral profile includes a spectral envelope. 
     
     
         6 . The method of  claim 1  wherein the second frequency region is higher than the first frequency region. 
     
     
         7 . The method of  claim 1  wherein the number of spectral components varies in time. 
     
     
         8 . The method of  claim 1  wherein the audio processing apparatus is implemented as part of an MPEG decoder. 
     
     
         9 . The method of  claim 1  wherein the adaptive grouping represents one or more auditory events. 
     
     
         10 . An apparatus for processing an encoded audio signal, the apparatus comprising:
 an audio decoder that decodes the encoded audio signal to obtain a time-domain audio signal, the encoded audio signal including spectral components from at least two channels of audio content;   a filter bank that analyzes the time-domain audio signal to obtain a plurality of complex-valued subband samples in a first frequency region for each of the at least two channels of audio content; and   one or more processors that for each of the at least two channels of audio content:
 generate a plurality of subband samples in a second frequency region based at least in part on the complex-valued subband samples in the first frequency region, 
 group at least some of the plurality of subband samples in the second frequency region with an adaptive time resolution and an adaptive frequency resolution to obtain an adaptive grouping, and 
 determine a spectral profile of at least some of the subband samples in the second frequency region based at least in part on the adaptive grouping; 
   wherein the apparatus is implemented at least in part in hardware, a parameter in the encoded audio signal indicates the adaptive frequency resolution for each of the at least two channels of audio content by specifying either a first frequency resolution or a second frequency resolution for each of the at least two channels of audio content, and the first frequency resolution is finer than the second frequency resolution.   
     
     
         11 . The apparatus of  claim 10  wherein the adaptive grouping is signaled in the encoded audio signal as one or more parameters. 
     
     
         12 . The apparatus of  claim 11  wherein the one or more parameters are used to determine a start time border and an end time border of a time segment. 
     
     
         13 . The apparatus of  claim 12  wherein an end time border of a first time segment is a start time border of a second time segment. 
     
     
         14 . The apparatus of  claim 10  wherein the spectral profile includes a spectral envelope. 
     
     
         15 . The apparatus of  claim 10  wherein the second frequency region is higher than the first frequency region. 
     
     
         16 . The apparatus of  claim 10  wherein the number of spectral components varies in time. 
     
     
         17 . The apparatus of  claim 10  wherein the audio processing apparatus is implemented as part of an MPEG decoder. 
     
     
         18 . The apparatus of  claim 10  wherein the adaptive grouping represents one or more auditory events.