chaosmeasure.cpp - Android社区 - https://www.androidos.net.cn/

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

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)
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Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
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This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright holders and contributors
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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 Audio Encoder **************************

Initial author:       M. Werner
   contents/description: Chaos measure calculation

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

#include "chaosmeasure.h"

/*****************************************************************************
    functionname: FDKaacEnc_FDKaacEnc_CalculateChaosMeasurePeakFast
    description:  Eberlein method of chaos measure calculation by high-pass
                  filtering amplitude spectrum
                  A special case of FDKaacEnc_CalculateChaosMeasureTonalGeneric --
                  highly optimized
*****************************************************************************/
static void
FDKaacEnc_FDKaacEnc_CalculateChaosMeasurePeakFast( FIXP_DBL  *RESTRICT paMDCTDataNM0,
                               INT        numberOfLines,
                               FIXP_DBL  *RESTRICT chaosMeasure )
{
  INT i, j;

/* calculate chaos measure by "peak filter" */
  for (i=0; i<2; i++) {
    /* make even and odd pass through data */
    FIXP_DBL left,center; /* left, center tap of filter */

left   = (FIXP_DBL)((LONG)paMDCTDataNM0[i]^((LONG)paMDCTDataNM0[i]>>(DFRACT_BITS-1)));
    center = (FIXP_DBL)((LONG)paMDCTDataNM0[i+2]^((LONG)paMDCTDataNM0[i+2]>>(DFRACT_BITS-1)));

for (j = i+2; j < numberOfLines - 2; j+=2) {
      FIXP_DBL right = (FIXP_DBL)((LONG)paMDCTDataNM0[j+2]^((LONG)paMDCTDataNM0[j+2]>>(DFRACT_BITS-1)));
      FIXP_DBL tmp = (left>>1)+(right>>1);

if (tmp < center ) {
         INT leadingBits = CntLeadingZeros(center)-1;
         tmp = schur_div(tmp<<leadingBits, center<<leadingBits, 8);
         chaosMeasure[j] = fMult(tmp,tmp);
      }
      else {
         chaosMeasure[j] = (FIXP_DBL)MAXVAL_DBL;
      }

left   = center;
      center = right;
    }
  }

/* provide chaos measure for first few lines */
  chaosMeasure[0] = chaosMeasure[2];
  chaosMeasure[1] = chaosMeasure[2];

/* provide chaos measure for last few lines */
  for (i = (numberOfLines-3); i < numberOfLines; i++)
    chaosMeasure[i] = FL2FXCONST_DBL(0.5);
}

/*****************************************************************************
    functionname: FDKaacEnc_CalculateChaosMeasure
    description:  calculates a chaosmeasure for every line, different methods
                  are available. 0 means tonal, 1 means noiselike
    returns:
    input:        MDCT data, number of lines
    output:       chaosMeasure
*****************************************************************************/
void
FDKaacEnc_CalculateChaosMeasure( FIXP_DBL    *paMDCTDataNM0,
                       INT          numberOfLines,
                       FIXP_DBL    *chaosMeasure )

{
    FDKaacEnc_FDKaacEnc_CalculateChaosMeasurePeakFast( paMDCTDataNM0,
                                   numberOfLines,
                                   chaosMeasure );
}

C++程序 | 162行 | 7.42 KB

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