Hybrid Permanent/Reversible Dynamic Range Control System

Abstract

A technique for controlling audio dynamic range in a manner that can be permanent, reversible, or anywhere in between, and can accomplish this goal in the baseband PCM or encoded domains.

1 . A method for controlling the dynamic range of an audio signal in a hybrid permanent/reversible manner, the method comprising:
 applying original audio to a detector and generating a control signal;   applying the same original audio to a first gain control element;   producing a permanently controlled output signal by varying this first gain control element with the control signal to raise or lower the level of the signal so that the loudest and quietest parts are brought closer to a target level;   applying the same control signal to a block formatter to match the capabilities of an audio encoder;   creating an inverse of this block formatted gain control signal;   passing this inverse block formatted signal through a control element to allow all, some, or none of the inverse block formatted signal to pass;   producing “remainder audio” by applying the permanently controlled output signal to a second gain control element to “un-apply” the actions of the original gain control within the boundaries of the block formatted signal;   applying this remainder audio to an audio encoder;   delaying the non-inverse block based control signal; and   using this delayed version of the non-inverse block based control signal as part of the encoding process representing one or more metadata elements.