Inversion of dynamic range control

A method of declipping a clipped audio signal that has been clipped by a dynamic range control, DRC, model, the method comprising:

• receiving the clipped audio signal;
• determining parameters of the DRC model that have been used for clipping the clipped audio signal;
• increasing the dynamic range of the clipped audio signal based on the determined parameters of the DRC model,
• wherein the DRC model is a soft-knee DRC model or a hard-knee DRC model and is defined by a control value that is applied to an envelope of an input audio signal;
• and
• wherein the control value comprises a constant gain portion and a variable gain portion.

A method of reversing dynamic range control, DRC, of a dynamic range controlled audio signal by estimating an input audio signal that would yield the dynamic range controlled audio signal when being fed to a DRC model using a set of parameters,

• wherein the DRC model is a soft-knee DRC model or a hard-knee DRC model and is defined by a control value that is applied to an envelope of the input audio signal, and wherein the control value comprises a static gain function,
• the method comprising:
• receiving, as inputs, the dynamic range controlled audio signal and the set of parameters of the DRC model;
• and
• for each sample of the dynamic range controlled signal:
• determining a characteristic function for the static gain function, wherein the characteristic function for the static gain function is a polynomial function of the envelope of the input audio signal and depends on one or more of the set of parameters of the DRC model;
• and
• determining the envelope of the input audio signal based on the characteristic function.