Apparatus and method for generating audio subband values and apparatus and method for generating time-domain audio samples

An apparatus for generating time-domain audio samples, comprising:

• a calculator for calculating a sequence of intermediate time-domain samples from audio subband values in audio subband channels, the sequence comprising earlier intermediate time-domain samples and later time-domain samples;
• a synthesis windower for windowing the sequence of intermediate time-domain samples using a synthesis window function comprising a sequence of window coefficients to acquire windowed intermediate time-domain samples, the synthesis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function;
• and
• wherein the second number is even;
• and
• an overlap-adder output stage for processing the windowed intermediate time-domain samples to acquire the time-domain samples.

A method for generating audio subband values in audio subband channels, comprising:

• windowing, by an analysis windower, a frame of time-domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function to acquire windowed samples, the analysis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation by window coefficients of the larger window function;
• and
• wherein the second number is an even number;
• and
• calculating, by a calculator, the audio subband values using the windowed samples,
• wherein at least one of the analysis windower and the calculator comprises a hardware implementation.

A method for generating time-domain audio samples, comprising:

• calculating, by a calculator, a sequence of intermediate time-domain samples from audio subband values in audio subband channels, the sequence comprising earlier intermediate time-domain samples and later intermediate time-domain samples;
• windowing, by a synthesis windower, the sequence of intermediate time-domain samples using a synthesis window function to acquire windowed time-domain samples, the synthesis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function;
• and
• wherein the second number is even;
• and
• overlap-adding, by an overlap-adder output stage, the windowed time-domain samples to acquire the time-domain samples;
• wherein at least one of the synthesis windower, the calculator and the overlap-adder output stage comprises a hardware implementation.

A non-transitory storage medium having stored thereon a program with a program code for executing a method for generating audio subband values in audio subband channels, the method comprising:

• windowing a frame of time-domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function to acquire windowed samples, the analysis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation by window coefficients of the larger window function;
• and
• wherein the second number is an even number;
• and
• calculating the audio subband values using the windowed samples,
• when running on a processor.

A non-transitory storage medium having stored thereon a program with a program code for executing a method for generating time-domain audio samples, the method comprising:

• calculating a sequence of intermediate time-domain samples from audio subband values in audio subband channels, the sequence comprising earlier intermediate time-domain samples and later intermediate time-domain samples;
• windowing the sequence of intermediate time-domain samples using a synthesis window function to acquire windowed time-domain samples, the synthesis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function;
• and
• wherein the second number is even;
• and
• overlap-adding the windowed time-domain samples to acquire the time-domain samples,
• when running on a processor.

An apparatus for generating audio subband values in audio subband channels, comprising:

• an analysis windower for windowing a frame of time-domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function comprising a sequence of window coefficients to acquire windowed samples, the analysis window function comprising a first number of window coefficients derived from a larger window function comprising a sequence of a larger second number of window coefficients,
• wherein the window coefficients of the window function are derived by an interpolation of window coefficients of the larger window function;
• and
• wherein the second number is an even number;
• and
• a calculator for calculating the audio subband values using the windowed samples,
• wherein the analysis windower is adapted such that the windowing comprises multiplying the time-domain audio input samples x(n) of the frame to acquire the windowed samples z(n) of the windowed frame based on the equation
• z(n)=x(n)·c(n)
• wherein n is an integer indicating an index of the sequence of window coefficients in the range of 0 to T·N−1, wherein c(n) is the window coefficient of the analysis window function corresponding to the index n, wherein x(N·T−1) is the latest time-domain audio input sample of the frame of time-domain audio input samples, wherein the analysis windower is adapted such that the frame of time-domain audio input samples comprises a sequence of T blocks of time-domain audio input samples extending from the earliest to the latest time-domain audio input samples of the frame, each block comprising N time-domain audio input samples, and wherein T and N are positive integers and T is larger than 4.