Techniques for distortion reducing multi-band compressor with timbre preservation
AssigneeDolby Laboratories Licensing Corporation
InventorAlan J. Seefeldt
Life of this patent
Estimating the term…
Abstract
Distortion reducing multi-band compressor with timbre preservation is provided. Timbre preservation is achieved by determining a time-varying threshold in each of a plurality frequency bands as a function of a respective fixed threshold for the frequency band and, at least in part, an audio signal level and a fixed threshold outside such frequency band. If a particular frequency band receives significant gain reduction due to being above or approaching its fixed threshold, then a time-varying threshold of one or more other frequency bands are also decreased to receive some gain reduction. In a specific embodiment, time-varying thresholds can be computed from an average difference of the audio input signal in each frequency band and its respective fixed threshold.
Claims10
A system comprising:
- a multi-band filterbank configured to split an audio signal (x[n]) for a plurality of frequency bands;
- a timbre preservation element coupled to the multi-band filterbank and configured to receive a fixed threshold (Lb) for each frequency band, to receive the split audio signal (xb[n]) for each frequency band and to compute a time-varying threshold (Tb[n]) for each frequency band;
- and
- compression function elements coupled to the timbre preservation, each compression function element being dedicated to a respective frequency band of the plurality of frequency bands and configured to receive the split audio signal (xb[n]) for the respective frequency band, to receive the time-varying threshold (Tb[n]) for the respective frequency band, and to determine a gain (gb[n]) for the respective frequency band based on the respective time-varying threshold (Tb[n]) for the respective frequency band and the respective split audio signal (xb[n]) for the respective frequency band,
- wherein the timbre preservation element (106) is configured to compute the time-varying threshold (Tb[n]) for a first frequency band of said plurality of frequency bands using an estimated power level for the split audio signal (xb[n]) for a frequency band of said plurality of frequency bands outside the first frequency band.
A method comprising:
- splitting, in a multi-band filterbank, an audio signal (x[n]) for a plurality of frequency bands;
- in a timbre preservation element coupled to the multi-band filterbank:
- receiving fixed thresholds (Lb) for each frequency band;
- receiving the split audio signal (xb[n]) for each frequency band, and
- computing a time-varying threshold (Tb[n]) for each frequency band;
- in a compression function element coupled to the timbre preservation element and dedicated to a respective frequency band of the plurality of frequency bands:
- receiving the split audio signal (xb[n]) for the respective frequency band;
- receiving the time-varying threshold (Tb[n]) for the respective frequency band, and
- determining a gain (gb[n]) for the respective frequency band based on the respective time-varying threshold (Tb[n]) for the respective frequency band and the respective split audio signal (xb[n]) for the respective frequency band,
- wherein the time-varying threshold (Tb[n]) for a first frequency band is computed using an estimated power level for the split audio signal (xb[n]) for a frequency band of said plurality of frequency bands outside the first frequency band.
Dependencies are inferred from the claim text.