Patent ID: 7369906

Claim:
A digital audio processing apparatus for processing a sequence of input digital audio sample values representing an input digital audio signal to generate a respective sequence of output digital audio sample values representing an output digital audio signal, said apparatus comprising: a first digital audio sample mapping module operable to apply a quasi time-invariant transfer function to each input digital audio sample value to calculate a first output digital audio sample value from a given input digital audio sample value using said transfer function, said transfer function being arranged so that a ratio of root mean square signal level to peak signal magnitude is lower for said input digital audio signal than for a corresponding portion of said output digital audio signal; a user control operable to modify said time-invariant transfer function, wherein said user control is operable to set a value of a user-adjustable variable α, where 0 ≦α<1; a first multiplier operable to multiply said first output digital audio sample value by said user-adjustable variable α to produce a first modified output sample value; a second digital audio sample mapping module operable to calculate a second output digital audio sample value from said given input digital sample value using a further, different transfer function; a second multiplier operable to multiply said second output digital audio sample value by a variable (1−α) to produce a second modified output sample value; and an adder operable to add said first modified output sample value and said second modified output sample value.