static void equalizer_state_compute_impulse_response(EqualizerState *s){
void *fft_handle=ms_fft_init(s->nfft);
ms_message("Spectral domain:");
dump_table(s->fft_cpx,s->nfft);
ms_ifft(fft_handle,s->fft_cpx,s->fir);
ms_fft_destroy(fft_handle);
/*
ms_message("Inverse fft result:");
dump_table(s->fir,s->fir_len);
*/
time_shift(s->fir,s->fir_len);
/*
ms_message("Time shifted:");
dump_table(s->fir,s->fir_len);
*/
norm_and_apodize(s->fir,s->fir_len);
ms_message("Apodized impulse response:");
dump_table(s->fir,s->fir_len);
s->needs_update=FALSE;
}
void generic_plc_fftbf(plc_context_t *context, int16_t *input_buffer, int16_t *output_buffer, size_t input_buffer_len) {
/* Allocate temporary buffers to perform FFT-> double buffer size in frequency domain -> inverse FFT */
ms_word16_t *time_domain_buffer = ms_malloc0(input_buffer_len*sizeof(ms_word16_t));
ms_word16_t *freq_domain_buffer = ms_malloc0(input_buffer_len*sizeof(ms_word16_t));
ms_word16_t *freq_domain_buffer_double = ms_malloc0(2*input_buffer_len*sizeof(ms_word16_t));
ms_word16_t *time_domain_buffer_double = ms_malloc0(2*input_buffer_len*sizeof(ms_word16_t));
size_t i;
/* convert to ms_word16_t the input buffer */
for (i=0; i<input_buffer_len; i++) {
time_domain_buffer[i] = (ms_word16_t)((float)input_buffer[i]*context->hamming_window[i]);
}
/* FFT */
ms_fft(context->fft_to_frequency_context, time_domain_buffer, freq_domain_buffer);
/* double the number of sample in frequency domain */
for (i=0; i<input_buffer_len; i++) {
freq_domain_buffer_double[2*i] = freq_domain_buffer[i]*ENERGY_ATTENUATION;
freq_domain_buffer_double[2*i+1] = 0;//freq_domain_buffer[i]/2 ;
}
/* inverse FFT, we have twice the number of original samples, discard the first half and use the second as new samples */
ms_ifft(context->fft_to_time_context, freq_domain_buffer_double, time_domain_buffer_double);
ms_free(time_domain_buffer);
ms_free(freq_domain_buffer);
ms_free(freq_domain_buffer_double);
/* copy generated signal to the plc_out_buffer */
for (i=0; i<2*input_buffer_len; i++) {
output_buffer[i] = (int16_t)(time_domain_buffer_double[i]);
}
ms_free(time_domain_buffer_double);
}
