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Apply deemphasis to both channels in the same loop for the simple case

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This makes the decoder ~2.5% faster on x86 because the stereo loop
takes the same processing time as one mono loop due to the dependency chain
This commit is contained in:
Jean-Marc Valin 2016-08-14 17:56:45 -04:00
parent cd159fd1ec
commit 11dba8d902
1 changed files with 38 additions and 0 deletions
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38
celt/celt_decoder.c
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@ -177,6 +177,36 @@ void opus_custom_decoder_destroy(CELTDecoder *st)
}
#endif /* CUSTOM_MODES */
#ifndef CUSTOM_MODES
/* Special case for stereo with no downsampling and no accumulation. This is
quite common and we can make it faster by processing both channels in the
same loop, reducing overhead due to the dependency loop in the IIR filter. */
static void deemphasis_stereo_simple(celt_sig *in[], opus_val16 *pcm, int N, const opus_val16 coef0,
celt_sig *mem)
{
celt_sig * OPUS_RESTRICT x0;
celt_sig * OPUS_RESTRICT x1;
celt_sig m0, m1;
int j;
x0=in[0];
x1=in[1];
m0 = mem[0];
m1 = mem[1];
for (j=0;j<N;j++)
{
celt_sig tmp0, tmp1;
/* Add VERY_SMALL to x[] first to reduce dependency chain. */
tmp0 = x0[j] + VERY_SMALL + m0;
tmp1 = x1[j] + VERY_SMALL + m1;
m0 = MULT16_32_Q15(coef0, tmp0);
m1 = MULT16_32_Q15(coef0, tmp1);
pcm[2*j ] = SCALEOUT(SIG2WORD16(tmp0));
pcm[2*j+1] = SCALEOUT(SIG2WORD16(tmp1));
}
mem[0] = m0;
mem[1] = m1;
}
#endif
#ifndef RESYNTH
static
@ -190,6 +220,14 @@ void deemphasis(celt_sig *in[], opus_val16 *pcm, int N, int C, int downsample, c
opus_val16 coef0;
VARDECL(celt_sig, scratch);
SAVE_STACK;
#ifndef CUSTOM_MODES
/* Short version for common case. */
if (downsample == 1 && C == 2 && !accum)
{
deemphasis_stereo_simple(in, pcm, N, coef[0], mem);
return;
}
#endif
#ifndef FIXED_POINT
(void)accum;
celt_assert(accum==0);