Frequency domain multiband dynamics compressor with spectral balance compensation

Abstract

A multiband dynamics compressor implements a solution for minimizing unwanted changes to the long-term frequency response. The solution essentially proposes undoing the multiband compression in a controlled manner using much slower smoothing times. In this regard, the compensation provided acts more like an equalizer than a compressor. What is applied is a very slowly time-varying, frequency-dependent post-gain (make-up gain) that attempts to restore the smoothed long-term level of each compressor band.

What is claimed is: 
     
         1 . A multiband dynamics compressor, comprising:
 a first computation block adapted to calculate, for a multiband input signal, a first long-term magnitude spectrum;   a multiband dynamics compressor adapted to perform multiband dynamics compression on the multiband input signal to generate a compressed multiband output signal;   a second computation block adapted to calculate, for the compressed multiband output signal, a second long-term magnitude spectrum;   a summing circuit adapted to sum the first long-term magnitude spectrum and second long-term magnitude spectrum to generate a multiband adjustment gain; and   a spectral balance compensation filter adapted to filter the compressed multiband output signals in response to the multiband adjustment gain.   
     
     
         2 . The compressor of  claim 1 , wherein the summing circuit is a difference circuit which calculates a difference between the first long-term spectral magnitude and second long-term spectral magnitude. 
     
     
         3 . The compressor of  claim 1 , wherein the input signal has a total length and the first long-term spectral magnitude and second long-term spectral magnitude are calculated over the total length of the input signal. 
     
     
         4 . The compressor of  claim 1 , wherein the first and second computation block implement a Fourier transform to generate spectral data. 
     
     
         5 . The compressor of  claim 1 , wherein the summing circuit calculates a difference between the long-term magnitude spectra. 
     
     
         6 . The compressor of  claim 5 , wherein the difference in magnitude of the long-term magnitude spectra in dB corresponds to a gain in dB set by the multiband adjustment gain. 
     
     
         7 . A method, comprising:
 first calculating, for a multiband input signal, a first long-term magnitude spectrum;   multiband dynamics compressing of the multiband input signal to generate a compressed multiband output signal;   second calculating, for the compressed multiband output signal, a second long-term magnitude spectrum;   summing the first long-term magnitude spectrum and second long-term magnitude spectrum to generate a multiband adjustment gain; and   spectral balance compensation filtering implemented by applying the multiband adjustment gain to the compressed multiband output signal.   
     
     
         8 . The method of  claim 7 , wherein summing comprises taking a difference between the first long-term spectral magnitude and second long-term spectral magnitude. 
     
     
         9 . The method of  claim 7 , wherein the input signal has a total length and the wherein first calculating the first long-term spectral magnitude and second calculating the second long-term spectral magnitude are calculated over the total length of the input signal. 
     
     
         10 . The method of  claim 7 , wherein summing comprises calculating a difference between the long-term magnitude spectra. 
     
     
         11 . The method of  claim 10 , wherein the difference in magnitude of the long-term magnitude spectra in dB corresponds to a gain in dB set by the multiband adjustment gain. 
     
     
         12 . A multiband dynamics compressor, comprising:
 a splitting block adapted to split a received signal into a plurality of frequency bands, each frequency band having a frequency band signal including a range of frequencies;   a dynamics compressor for each frequency band adapted to compress the frequency band signal; and   a combiner adapted to combine compressed signals output from the dynamics compressors to generate a compressor output signal;   wherein each dynamics compressor comprises:
 an input configured to receive a multiband input signal from the splitting block; 
 a multiband dynamics compressor adapted to perform multiband dynamics compression on the multiband input signal to generate a compressed multiband output signal; 
 a gain calculation block adapted to process the multiband input signal and compressed multiband output signal to generate a multiband adjustment gain; and 
 a spectral balance compensation filter adapted to filter the compressed multiband output signals in response to the multiband adjustment gain. 
   
     
     
         13 . The compressor of  claim 12 , wherein the gain calculation block comprises:
 a first computation block adapted to calculate, for the multiband input signal, a first long-term magnitude spectrum;   a second computation block adapted to calculate, for the compressed multiband output signal, a second long-term magnitude spectrum; and   a summing circuit adapted to sum the first long-term magnitude spectrum and second long-term magnitude spectrum to generate the multiband adjustment gain.   
     
     
         14 . The compressor of  claim 12 , wherein the splitting block comprises a fast Fourier transform (FFT) for processing the received signal to generate the plurality of frequency band signals. 
     
     
         15 . The compressor of  claim 12 , wherein the splitting block comprises a short-time Fourier transform (STFT) for processing the received signal to generate the plurality of frequency band signals. 
     
     
         16 . The compressor of  claim 12 , wherein the splitting block comprises a plurality of cross-over filters for processing the received signal to generate the plurality of frequency band signals. 
     
     
         17 . The compressor of  claim 12 , wherein the summing circuit is a difference circuit which calculates a difference between the first long-term spectral magnitude and second long-term spectral magnitude. 
     
     
         18 . The compressor of  claim 12 , wherein the input signal has a total length and the first long-term spectral magnitude and second long-term spectral magnitude are calculated over the total length of the input signal.