Multiband dynamics compressor with spectral balance compensation
View Patent ↗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.
1. 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:
a first computation block adapted to calculate, for the frequency band signal, a compressor gain value;
a second computation block adapted to calculate, for the frequency band signal and in response to the calculated compressor gain value, a spectral compensation gain value equal to a difference between the received frequency band signal and an estimate of an uncompensated frequency band signal compressed in accordance with the compressor gain value;
a summing circuit adapted to sum the compressor gain value and spectral compensation gain value to obtain a total gain value; and
a circuit to apply the total gain value against the frequency band signal to produce the compressed signal.
2. The compressor of claim 1 , wherein the splitting block comprises a fast Fourier transform (FFT) for processing the received signal to generate the plurality of frequency band signals.
3. The compressor of claim 1 , wherein the splitting block comprises a short-time Fourier transform (STFT) for processing the received signal to generate the plurality of frequency band signals.
4. The compressor of claim 1 , wherein the splitting block comprises a plurality of cross-over filters for processing the received signal to generate the plurality of frequency band signals.
5. The compressor of claim 1 , further comprising a scaling circuit adapted to scale the spectral compensation gain value prior to the summing circuit.
6. The compressor of claim 1 , wherein the second computation block comprises:
a summer circuit configured to sum the compressor gain value with the frequency band signal to generate the estimate of the uncompensated frequency band signal; and
a subtraction circuit configured to subtract the estimate of the uncompensated frequency band signal from the frequency band signal to generate the spectral compensation gain value.
7. The compressor of claim 6 , further comprising: a smoothing circuit configured to smooth the frequency band signal prior to subtracting and a smoothing circuit configured to smooth the estimate of the uncompensated frequency band signal prior to subtracting.
8. The compressor of claim 6 , further comprising a smoothing circuit configured to smooth the compressor gain value prior to summing.
9. 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:
a first computation block adapted to calculate, for the frequency band signal, a compressor gain value;
a second computation block adapted to calculate, for the frequency band signal and in response to the calculated compressor gain value, a spectral compensation gain value;
a summing circuit adapted to sum the compressor gain value and spectral compensation gain value to obtain a total gain value; and
a circuit to apply the total gain value against the frequency band signal to produce the compressed signal;
wherein the second computation block comprises:
a first smoothing circuit adapted to smooth a first signal derived from the frequency band signal and generate a first output;
a first summing circuit adapted to sum the compressor gain value with the first signal and generate a second output;
a second smoothing circuit adapted to smooth the second output and generate a third output; and
a second summing circuit adapted to sum the first output and the third output to generate the spectral compensation gain value.
10. The compressor of claim 9 , further comprising a third smoothing circuit adapted to smooth the compressor gain value prior to be summed by the first summing circuit.
11. The compressor of claim 9 , wherein the smoothing circuits comprise a non-linear recursive smoothing filter.
12. The compressor of claim 11 , wherein the non-linear recursive smoothing filter supports the use of unequal attack and release coefficients.
13. A method, comprising:
splitting a received signal into a plurality of frequency bands, each frequency band having a frequency band signal having a range of frequencies;
dynamics compressing each frequency band signal; and
combining compressed signals output from the dynamics compression to generate a compressor output signal;
wherein dynamics compressing of each frequency band signal comprises:
calculating, for the frequency band signal, a compressor gain value;
calculating, for the frequency band signal and in response to the calculated compressor gain value, a spectral compensation gain value equal to a difference between the received frequency band signal and an estimate of an uncompensated frequency band signal compressed in accordance with the compressor gain value;
summing the compressor gain value and spectral compensation gain value to obtain a total gain value; and
applying the total gain value against the signals of the frequency band to produce the compressed signal.
14. The method of claim 13 , wherein splitting comprises performing a fast Fourier transform (FFT) for processing the received signal to generate the frequency band signals.
15. The method of claim 13 , wherein splitting comprises performing a short-time Fourier transform (STFT) for processing the received signal to generate the frequency band signals.
16. The method of claim 13 , wherein splitting comprises performing crossover filtering for processing the received signal to generate the frequency band signals.
17. The method of claim 13 , further comprising scaling the spectral compensation gain value prior to summing.
18. The method of claim 13 , wherein calculating the spectral compensation gain value comprises:
summing the compressor gain value with the frequency band signal to generate the estimate of the uncompensated frequency band signal; and
subtracting the estimate of the uncompensated frequency band signal from the frequency band signal to generate the spectral compensation gain value.
19. The method of claim 18 , further comprising: smoothing the frequency band signal prior to subtracting and smoothing the estimate of the uncompensated frequency band signal prior to subtracting.
20. The method of claim 18 , further comprising smoothing the compressor gain value prior to summing.
21. A method, comprising:
splitting a received signal into a plurality of frequency bands, each frequency band having a frequency band signal having a range of frequencies;
dynamics compressing each frequency band signal; and
combining compressed signals output from the dynamics compression to generate a compressor output signal;
wherein dynamics compressing of each frequency band signal comprises:
calculating, for the frequency band signal, a compressor gain value;
calculating, for the frequency band signal and in response to the calculated compressor gain value, a spectral compensation gain value;
summing the compressor gain value and spectral compensation gain value to obtain a total gain value; and
applying the total gain value against the signals of the frequency band to produce the compressed signal;
wherein calculating the spectral compensation gain value comprises:
first smoothing a first signal derived from the frequency band signal to generate a first output;
first summing the compressor gain value with the first signal to generate a second output;
second smoothing the second output to generate a third output; and
second summing the first output and the third output to generate the spectral compensation gain value.
22. The method of claim 21 , further comprising third smoothing the compressor gain value prior to the first summing.
23. The method of claim 21 , wherein smoothing comprises implementing non-linear recursive smoothing filtering.
24. The method of claim 23 , wherein non-linear recursive smoothing filtering supports the use of unequal attack and release coefficients.