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Make deceodeSpectrum() store the spectral coefficients of odd bands in reverse order, rather than having to reverse them in IMLT(). Also saves 0.11MHz, ~0.16% speedup on PP5024.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24641 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Mohamed Tarek 2010-02-14 01:59:14 +00:00
parent ce1d2eda70
commit 8722c6f2bb
1 changed files with 11 additions and 19 deletions
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30
apps/codecs/libatrac/atrac3.c
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@ -189,23 +189,8 @@ static void iqmf (int32_t *inlo, int32_t *inhi, unsigned int nIn, int32_t *pOut,
* @param odd_band 1 if the band is an odd band
*/
static void IMLT(int32_t *pInput, int32_t *pOutput, int odd_band)
static void IMLT(int32_t *pInput, int32_t *pOutput)
{
int i;
if (odd_band) {
/**
* Reverse the odd bands before IMDCT, this is an effect of the QMF transform
* or it gives better compression to do it this way.
* FIXME: It should be possible to handle this in ff_imdct_calc
* for that to happen a modification of the prerotation step of
* all SIMD code and C code is needed.
* Or fix the functions before so they generate a pre reversed spectrum.
*/
for (i=0; i<128; i++)
FFSWAP(int32_t, pInput[i], pInput[255-i]);
}
/* Apply the imdct. */
mdct_backward(512, pInput, pOutput);
@ -365,8 +350,15 @@ static int decodeSpectrum (GetBitContext *gb, int32_t *pOut)
SF = fixmul31(SFTable_fixed[SF_idxs[cnt]], iMaxQuant_fix[subband_vlc_index[cnt]]);
/* Inverse quantize the coefficients. */
for (pIn=mantissas ; first<last; first++, pIn++)
pOut[first] = fixmul16(*pIn, SF);
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);
}
} else {
/* This subband was not coded, so zero the entire subband. */
memset(pOut+first, 0, subbWidth*sizeof(int32_t));
@ -740,7 +732,7 @@ static int decodeChannelSoundUnit (GetBitContext *gb, channel_unit *pSnd, int32_
for (band=0; band<4; band++) {
/* Perform the IMDCT step without overlapping. */
if (band <= numBands) {
IMLT(&(pSnd->spectrum[band*256]), pSnd->IMDCT_buf, band&1);
IMLT(&(pSnd->spectrum[band*256]), pSnd->IMDCT_buf);
} else
memset(pSnd->IMDCT_buf, 0, 512 * sizeof(int32_t));