Understanding Window Functions

The Intel IPP provides the following functions to generate window samples:

Bartlett windowing function
Blackman family of windowing functions
Hamming windowing function
Hann windowing function
Kaiser windowing function

These functions generate the window samples and multiply them into an existing signal. To obtain the window samples themselves, initialize the vector argument to the unity vector before calling the window function.

If you want to multiply different frames of a signal by the same window multiple times, it is better to first calculate the window by calling one of the windowing functions (ippsWinHann, for example) on a vector with all elements set to 1.0. Then use one of the vector multiplication functions (ippsMul, for example) to multiply the window into the signal each time a new set of input samples is available. This avoids repeatedly calculating the window samples. This is illustrated in the following code example.

Window and FFT Many Frames of a Signal

void multiFrameWin( void ) {

     Ipp32f win[LEN], x[LEN], X[LEN];

     IppsFFTSpec_R_32f* ctx;

     ippsSet_32f( 1, win, LEN );

     ippsWinHann_32f_I( win, LEN );

     /// ... initialize FFT context

     while(1 ){

        /// ... get x signal

///

        ippsMul_32f_I( win, x, LEN );

        ippsFFTFwd_RToPack_32f( x, X, ctx, 0 );