libAACdec/src/arm/block_arm.cpp

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

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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
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already be covered under those patent licenses when it is used for those
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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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Attention: Audio and Multimedia Departments - FDK AAC LL
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----------------------------------------------------------------------------- */

/**************************** AAC decoder library ******************************

   Author(s):   Arthur Tritthart

   Description: (ARM optimised) Scaling of spectral data

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

#define FUNCTION_CBlock_ScaleSpectralData_func1

/* Note: This loop is only separated for ARM in order to save cycles
         by loop unrolling. The ARM core provides by default a 5-cycle
         loop overhead per sample, that goes down to 1-cycle per sample
         with an optimal 4x-loop construct (do - 4x - while).
*/
static inline void CBlock_ScaleSpectralData_func1(
    FIXP_DBL *pSpectrum, int maxSfbs, const SHORT *RESTRICT BandOffsets,
    int SpecScale_window, const SHORT *RESTRICT pSfbScale, int window) {
  int band_offset = 0;
  for (int band = 0; band < maxSfbs; band++) {
    int runs = band_offset;
    band_offset = BandOffsets[band + 1];
    runs = band_offset - runs; /* is always a multiple of 4 */
    FDK_ASSERT((runs & 3) == 0);
    int scale =
        fMin(DFRACT_BITS - 1, SpecScale_window - pSfbScale[window * 16 + band]);

    if (scale) {
      do {
        FIXP_DBL tmp0, tmp1, tmp2, tmp3;
        tmp0 = pSpectrum[0];
        tmp1 = pSpectrum[1];
        tmp2 = pSpectrum[2];
        tmp3 = pSpectrum[3];
        tmp0 >>= scale;
        tmp1 >>= scale;
        tmp2 >>= scale;
        tmp3 >>= scale;
        *pSpectrum++ = tmp0;
        *pSpectrum++ = tmp1;
        *pSpectrum++ = tmp2;
        *pSpectrum++ = tmp3;
      } while ((runs = runs - 4) != 0);
    } else {
      pSpectrum += runs;
    }
  }
}