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Commit 9038972c authored by Jakub Pawlowski's avatar Jakub Pawlowski
Browse files

Add some missing math in DCTIV computation 

Time-frequency transformation was missing some multiplications, causing
audio quality issues.

Bug: 150670922
Tag: #feature
Test: Play music, observe quality improvement
Sponsor: jpawlowski@
Change-Id: Idab9949972ea746d5ff18eaa5a074137331a441e
parent 502596b4

system/embdrv/lc3/Common/DctIV.cpp

+35 −4
Original line number Original line Diff line number Diff line
@@ -116,6 +116,8 @@ class KissfftConfig { 
};

};





#elif defined USE_OWN_FFT

#elif defined USE_OWN_FFT

#include <complex>



#include "fft.h"

#include "fft.h"

#endif

#endif
@@ -136,7 +138,17 @@ DctIVDbl::DctIVDbl(uint16_t NF_) 
  dctIVconfig = new KissfftConfig(NF / 2);

  dctIVconfig = new KissfftConfig(NF / 2);





#elif defined USE_OWN_FFT

#elif defined USE_OWN_FFT

// setup is not needed



  int N = NF / 2;

  std::complex<double>* twiddle = new std::complex<double>[N];

  dctIVconfig = twiddle;

  const double pi = std::acos(-1);

  for (uint16_t n = 0; n < N; n++) {

    twiddle[n] =

        std::complex<double>(std::cos(-pi * (8 * n + 1) / (8.0 * N * 2)),

                             std::sin(-pi * (8 * n + 1) / (8.0 * N * 2)));

  }



#endif

#endif





  for (uint16_t n = 0; n < NF; n++) {

  for (uint16_t n = 0; n < NF; n++) {
@@ -159,7 +171,9 @@ DctIVDbl::~DctIVDbl() { 
  }

  }





#elif defined USE_OWN_FFT

#elif defined USE_OWN_FFT

// cleanup is not needed

  std::complex<double>* twiddle = (std::complex<double>*)dctIVconfig;

  delete[] twiddle;



#endif

#endif

  if (nullptr != in) {

  if (nullptr != in) {

    delete[] in;

    delete[] in;
@@ -250,6 +264,14 @@ void DctIVDbl::run() { 
    in[NF - n] = buffer;

    in[NF - n] = buffer;

  }

  }





  std::complex<double>* twiddle = (std::complex<double>*)dctIVconfig;

  for (uint16_t n = 0; n < NF / 2; n++) {

    double real = in[2 * n + 0];

    double imag = in[2 * n + 1];

    in[2 * n + 0] = real * twiddle[n].real() - imag * twiddle[n].imag();

    in[2 * n + 1] = real * twiddle[n].imag() + imag * twiddle[n].real();

  }



  for (uint16_t n = 0; n < NF / 2; n++) {

  for (uint16_t n = 0; n < NF / 2; n++) {

    inbuf[n].re = in[2 * n];

    inbuf[n].re = in[2 * n];

    inbuf[n].im = in[2 * n + 1];

    inbuf[n].im = in[2 * n + 1];
@@ -258,8 +280,17 @@ void DctIVDbl::run() { 
  fft_complex* actal_output = fft(false, inbuf, NF / 2, inbuf, outbuf);

  fft_complex* actal_output = fft(false, inbuf, NF / 2, inbuf, outbuf);





  for (uint16_t n = 0; n < NF / 2; n++) {

  for (uint16_t n = 0; n < NF / 2; n++) {

    out[2 * n] = actal_output[n].re;

    double real = actal_output[n].re;

    out[NF - 2 * n - 1] = actal_output[n].im;

    double imag = actal_output[n].im;

    out[2 * n + 0] = 2 * (real * twiddle[n].real() - imag * twiddle[n].imag());

    out[2 * n + 1] = 2 * (real * twiddle[n].imag() + imag * twiddle[n].real());

  }



  for (uint16_t n = 1; n < NF / 2; n += 2) {

    double buffer;

    buffer = out[n];

    out[n] = -out[NF - n];

    out[NF - n] = -buffer;

  }

  }





#else

#else