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 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.