Frequency domain multiband dynamics compressor with spectral balance compensation
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 signal processing system, comprising:
an input configured to receive a frequency band signal including a range of frequencies;
a first computation block configured to calculate, for the frequency band signal, a compressor gain value;
a second computation block configured 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 configured to sum the compressor gain value and spectral compensation gain value to obtain a total gain value; and
a circuit configured to apply the total gain value against the frequency band signal to produce a compressed output signal.
2. The signal processing system of claim 1 , further comprising a scaling circuit adapted to scale the spectral compensation gain value prior to the summing circuit.
3. The signal processing system 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.
4. The signal processing system of claim 3 , 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.
5. The signal processing system of claim 3 , further comprising a smoothing circuit configured to smooth the compressor gain value prior to summing.
6. The signal processing system of claim 1 , further comprising:
a gain calculation block configured to process the frequency band signal and compressed output signal to generate a adjustment gain; and
a spectral balance compensation filter configured to filter the compressed output signals in response to the multiband adjustment gain.
7. The signal processing system of claim 6 , wherein the gain calculation block comprises:
a first computation block adapted to calculate, for the frequency band signal, a first magnitude spectrum;
a second computation block adapted to calculate, for the compressed output signal, a second magnitude spectrum; and
a summing circuit adapted to sum the first magnitude spectrum and second magnitude spectrum to generate the adjustment gain.
8. The signal processing system of claim 7 , wherein the summing circuit is a difference circuit which calculates a difference between the first spectral magnitude and second spectral magnitude to generate a gain value.
9. The signal processing system of claim 8 , wherein the spectral balance compensation filter applies a gain corresponding to said gain value.