libSACenc/src/sacenc_filter.cpp

/* -----------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
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 1.    INTRODUCTION
The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software
that implements the MPEG Advanced Audio Coding ("AAC") encoding and decoding
scheme for digital audio. This FDK AAC Codec software is intended to be used on
a wide variety of Android devices.

AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient
general perceptual audio codecs. AAC-ELD is considered the best-performing
full-bandwidth communications codec by independent studies and is widely
deployed. AAC has been standardized by ISO and IEC as part of the MPEG
specifications.

Patent licenses for necessary patent claims for the FDK AAC Codec (including
those of Fraunhofer) may be obtained through Via Licensing
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already be covered under those patent licenses when it is used for those
licensed purposes only.

Commercially-licensed AAC software libraries, including floating-point versions
with enhanced sound quality, are also available from Fraunhofer. Users are
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information and documentation.

2.    COPYRIGHT LICENSE

Redistribution and use in source and binary forms, with or without modification,
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5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------- */

/*********************** MPEG surround encoder library *************************

   Author(s):   M. Multrus

   Description: Encoder Library
                Filter functions

*******************************************************************************/

/* Includes ******************************************************************/
#include "sacenc_filter.h"

/* Defines *******************************************************************/

/* Data Types ****************************************************************/
typedef struct T_DC_FILTER {
  FIXP_DBL c__FDK;
  FIXP_DBL state__FDK;

} DC_FILTER;

/* Constants *****************************************************************/

/* Function / Class Declarations *********************************************/

/* Function / Class Definition ***********************************************/
FDK_SACENC_ERROR fdk_sacenc_createDCFilter(HANDLE_DC_FILTER *hDCFilter) {
  FDK_SACENC_ERROR error = SACENC_OK;

  if (NULL == hDCFilter) {
    error = SACENC_INVALID_HANDLE;
  } else {
    FDK_ALLOCATE_MEMORY_1D(*hDCFilter, 1, DC_FILTER);
  }
  return error;

bail:
  fdk_sacenc_destroyDCFilter(hDCFilter);
  return ((SACENC_OK == error) ? SACENC_MEMORY_ERROR : error);
}

FDK_SACENC_ERROR fdk_sacenc_initDCFilter(HANDLE_DC_FILTER hDCFilter,
                                         const UINT sampleRate) {
  FDK_SACENC_ERROR error = SACENC_OK;

  FIXP_DBL expC;
  int s;

  /* Conversion for use of CalcInvLdData: e^x = 2^(x*log10(e)/log10(2) =
     CalcInvLdData(x*log10(e)/log10(2)/64.0) 1.44269504089 = log10(e)/log10(2)
     0.5           = scale constant value with 1 Bits
  */
  expC = fDivNormHighPrec((FIXP_DBL)20, (FIXP_DBL)sampleRate, &s);
  expC = fMultDiv2(FL2FXCONST_DBL(-1.44269504089 * 0.5), expC) >>
         (LD_DATA_SHIFT - 1 - 1);

  if (s < 0)
    expC = expC >> (-s);
  else
    expC = expC << (s);

  expC = CalcInvLdData(expC);

  hDCFilter->c__FDK = expC;
  hDCFilter->state__FDK = FL2FXCONST_DBL(0.0f);

  return error;
}

FDK_SACENC_ERROR fdk_sacenc_destroyDCFilter(HANDLE_DC_FILTER *hDCFilter) {
  FDK_SACENC_ERROR error = SACENC_OK;

  if ((hDCFilter != NULL) && (*hDCFilter != NULL)) {
    FDKfree(*hDCFilter);

    *hDCFilter = NULL;
  }

  return error;
}

FDK_SACENC_ERROR fdk_sacenc_applyDCFilter(HANDLE_DC_FILTER hDCFilter,
                                          const INT_PCM *const signalIn,
                                          INT_PCM *const signalOut,
                                          const INT signalLength) {
  FDK_SACENC_ERROR error = SACENC_OK;

  if ((hDCFilter == NULL) || (signalIn == NULL) || (signalOut == NULL)) {
    error = SACENC_INVALID_HANDLE;
  } else {
    const INT_PCM *const x = signalIn;
    INT_PCM *const y = signalOut;
    const FIXP_DBL c = hDCFilter->c__FDK;
    FIXP_DBL *const state = &hDCFilter->state__FDK;
    int i;
    FIXP_DBL x0, x1, y1;

    x1 = x0 = FX_PCM2FX_DBL(x[0]) >> DC_FILTER_SF;
    y1 = x0 + (*state);

    for (i = 1; i < signalLength; i++) {
      x0 = FX_PCM2FX_DBL(x[i]) >> DC_FILTER_SF;
      y[i - 1] = FX_DBL2FX_PCM(y1);
      y1 = x0 - x1 + fMult(c, y1);
      x1 = x0;
    }

    *state = fMult(c, y1) - x1;
    y[i - 1] = FX_DBL2FX_PCM(y1);
  }

  return error;
}