xref: /aosp_15_r20/external/aac/libAACenc/src/pre_echo_control.cpp (revision e54365361535b070c2db7374cec45c159c7d0e7a)

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

© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
Forschung e.V. All rights reserved.

 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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the purpose of encoding or decoding bit streams in products that are compliant
with the ISO/IEC MPEG audio standards. Please note that most manufacturers of
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directly from the patent owners, and therefore FDK AAC Codec software may
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
encouraged to check the Fraunhofer website for additional applications
information and documentation.

2.    COPYRIGHT LICENSE

Redistribution and use in source and binary forms, with or without modification,
are permitted without payment of copyright license fees provided that you
satisfy the following conditions:

You must retain the complete text of this software license in redistributions of
the FDK AAC Codec or your modifications thereto in source code form.

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Fraunhofer provides no warranty of patent non-infringement with respect to this
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You may use this FDK AAC Codec software or modifications thereto only for
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This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright
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Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
[email protected]
----------------------------------------------------------------------------- */

/**************************** AAC encoder library ******************************

   Author(s):   M.Werner

   Description: Pre echo control

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

#include "pre_echo_control.h"
#include "psy_configuration.h"

void FDKaacEnc_InitPreEchoControl(FIXP_DBL *RESTRICT pbThresholdNm1,
                                  INT *calcPreEcho, INT numPb,
                                  FIXP_DBL *RESTRICT sfbPcmQuantThreshold,
                                  INT *mdctScalenm1) {
  *mdctScalenm1 = PCM_QUANT_THR_SCALE >> 1;

  FDKmemcpy(pbThresholdNm1, sfbPcmQuantThreshold, numPb * sizeof(FIXP_DBL));

  *calcPreEcho = 1;
}

void FDKaacEnc_PreEchoControl(FIXP_DBL *RESTRICT pbThresholdNm1,
                              INT calcPreEcho, INT numPb,
                              INT maxAllowedIncreaseFactor,
                              FIXP_SGL minRemainingThresholdFactor,
                              FIXP_DBL *RESTRICT pbThreshold, INT mdctScale,
                              INT *mdctScalenm1) {
  int i;
  FIXP_DBL tmpThreshold1, tmpThreshold2;
  int scaling;

  /* If lastWindowSequence in previous frame was start- or stop-window,
     skip preechocontrol calculation */
  if (calcPreEcho == 0) {
    /* copy thresholds to internal memory */
    FDKmemcpy(pbThresholdNm1, pbThreshold, numPb * sizeof(FIXP_DBL));
    *mdctScalenm1 = mdctScale;
    return;
  }

  if (mdctScale > *mdctScalenm1) {
    /* if current thresholds are downscaled more than the ones from the last
     * block */
    scaling = 2 * (mdctScale - *mdctScalenm1);
    for (i = 0; i < numPb; i++) {
      /* multiplication with return data type fract ist equivalent to int
       * multiplication */
      FDK_ASSERT(scaling >= 0);
      tmpThreshold1 = maxAllowedIncreaseFactor * (pbThresholdNm1[i] >> scaling);
      tmpThreshold2 = fMult(minRemainingThresholdFactor, pbThreshold[i]);

      FIXP_DBL tmp = pbThreshold[i];

      /* copy thresholds to internal memory */
      pbThresholdNm1[i] = tmp;

      tmp = fixMin(tmp, tmpThreshold1);
      pbThreshold[i] = fixMax(tmp, tmpThreshold2);
    }
  } else {
    /* if thresholds of last block are more downscaled than the current ones */
    scaling = 2 * (*mdctScalenm1 - mdctScale);
    for (i = 0; i < numPb; i++) {
      /* multiplication with return data type fract ist equivalent to int
       * multiplication */
      tmpThreshold1 = (maxAllowedIncreaseFactor >> 1) * pbThresholdNm1[i];
      tmpThreshold2 = fMult(minRemainingThresholdFactor, pbThreshold[i]);

      /* copy thresholds to internal memory */
      pbThresholdNm1[i] = pbThreshold[i];

      FDK_ASSERT(scaling >= 0);
      if ((pbThreshold[i] >> (scaling + 1)) > tmpThreshold1) {
        pbThreshold[i] = tmpThreshold1 << (scaling + 1);
      }
      pbThreshold[i] = fixMax(pbThreshold[i], tmpThreshold2);
    }
  }

  *mdctScalenm1 = mdctScale;
}