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Minor atrac3 codec optimization. Refacturate requantization of spectral lines, unroll loops.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24672 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2010-02-15 20:20:52 +00:00
parent f38efac9e2
commit 86fc47c33a
1 changed files with 47 additions and 10 deletions
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57
apps/codecs/libatrac/atrac3.c
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@ -373,18 +373,62 @@ static void readQuantSpectralCoeffs (GetBitContext *gb, int selector, int coding
}
/**
* Requantize the spectrum.
*
* @param *mantissas pointer to mantissas for each spectral line
* @param pOut requantized band spectrum
* @param first first spectral line in subband
* @param last last spectral line in subband
* @param SF scalefactor for all spectral lines of this band
*/
static void inverseQuantizeSpectrum(int *mantissas, int32_t *pOut,
int32_t first, int32_t last, int32_t SF)
{
int *pIn = mantissas;
/* Inverse quantize the coefficients. */
if((first/256) &1) {
/* Odd band - Reverse coefficients */
do {
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
pOut[last--] = fixmul16(*pIn++, SF);
} while (last>first);
} else {
/* Even band - Do not reverse coefficients */
do {
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
pOut[first++] = fixmul16(*pIn++, SF);
} while (first<last);
}
}
/**
* Restore the quantized band spectrum coefficients
*
* @param gb the GetBit context
* @param pOut decoded band spectrum
* @return outSubbands subband counter, fix for broken specification/files
* @return outSubbands subband counter, fix for broken specification/files
*/
int decodeSpectrum (GetBitContext *gb, int32_t *pOut) ICODE_ATTR;
int decodeSpectrum (GetBitContext *gb, int32_t *pOut)
{
int numSubbands, codingMode, cnt, first, last, subbWidth, *pIn;
int numSubbands, codingMode, cnt, first, last, subbWidth;
int subband_vlc_index[32], SF_idxs[32];
int mantissas[128];
int32_t SF;
@ -423,14 +467,7 @@ int decodeSpectrum (GetBitContext *gb, int32_t *pOut)
SF <<= 2;
/* Inverse quantize the coefficients. */
if((first/256) &1) {
/* Odd band - Reverse coefficients */
for (pIn=mantissas ; last>first; last--, pIn++)
pOut[last] = fixmul16(*pIn, SF);
} else {
for (pIn=mantissas ; first<last; first++, pIn++)
pOut[first] = fixmul16(*pIn, SF);
}
inverseQuantizeSpectrum(mantissas, pOut, first, last, SF);
} else {
/* This subband was not coded, so zero the entire subband. */