Patent ID: 11961528
Assignee: DOLBY INTERNATIONAL AB
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 7:
8. An audio processing unit for performing high frequency reconstruction of an audio signal, the audio processing unit comprising:
an input interface for receiving an encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of the audio signal and high frequency reconstruction metadata;
a core audio decoder for decoding the audio data to generate a decoded lowband audio signal;
a deformatter for extracting from the encoded audio bitstream the high frequency reconstruction metadata, the high frequency reconstruction metadata including operating parameters for a high frequency reconstruction process, the operating parameters including a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes a backward-compatible extension container including a patching mode parameter, wherein a first value of the patching mode parameter indicates spectral translation and a second value of the patching mode parameter indicates harmonic transposition by phase-vocoder frequency spreading, and wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6;
an analysis filterbank for filtering the decoded lowband audio signal to generate a filtered lowband audio signal, wherein the filtering is performed by an analysis filterbank that includes analysis filters, hk(n), that are modulated versions of a prototype filter, p0(n), according to:, h
     k
    
    (
    n
    )
   
   =
   
    
     
      p
      0
     
     (
     n
     )
    
    ⁢
      
    exp
    ⁢
      
    
     {
     
      i
      ⁢
      
       π
       M
      
      ⁢
      
       (
       
        k
        +
        
         1
         2
        
       
       )
      
      ⁢
        
      
       (
       
        n
        -
        
         N
         2
        
       
       )
      
     
     }
    
   
  
  ,
 

 
  
   0
   ≤
   n
   ≤
   N
  
  ;
 

 
  0
  ≤
  k
  <
  M, where p0(n) is a real-valued symmetric or asymmetric prototype filter, M is a number of channels in the analysis filterbank and N is an order of the prototype filter, wherein the prototype filter, p0(n), is derived from coefficients of Table 4 herein; and
a high frequency regenerator for reconstructing a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata, wherein the reconstructing includes a spectral translation if the patching mode parameter is the first value and the reconstructing includes harmonic transposition by phase-vocoder frequency spreading if the patching mode parameter is the second value.