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Increasing the temporal resolution of transients

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Apply a one-level Haar transform (or Hadamard) on each short MDCT
to nearly double the time-domain resolution.
This commit is contained in:
Jean-Marc Valin 2010-05-21 15:44:06 -04:00
parent 9f89cab6ec
commit 791cfe1f0a
1 changed files with 35 additions and 2 deletions
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37
libcelt/bands.c
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@ -452,6 +452,19 @@ static void deinterleave_vector(celt_norm *X, int N0, int stride)
RESTORE_STACK;
}
static void haar1(celt_norm *X, int N0, int stride)
{
int i, j;
N0 >>= 1;
for (i=0;i<stride;i++)
for (j=0;j<N0;j++)
{
celt_norm tmp = X[stride*2*j+i];
X[stride*2*j+i] = MULT16_16_Q15(QCONST16(.7070678f,15), X[stride*2*j+i] + X[stride*(2*j+1)+i]);
X[stride*(2*j+1)+i] = MULT16_16_Q15(QCONST16(.7070678f,15), tmp - X[stride*(2*j+1)+i]);
}
}
/* This function is responsible for encoding and decoding a band for both
the mono and stereo case. Even in the mono case, it can split the band
in two and transmit the energy difference with the two half-bands. It
@ -466,19 +479,33 @@ static void quant_band(int encode, const CELTMode *m, int i, celt_norm *X, celt_
int imid=0, iside=0;
int N0=N;
int N_B=N;
int N_B0;
int spread0=spread;
int do_haar = 0;
if (spread)
N_B /= spread;
N_B0 = N_B;
split = stereo = Y != NULL;
if (!stereo && spread>1 && level==0)
{
if ((N_B&1) == 0)
{
spread <<= 1;
N_B >>= 1;
do_haar = 1;
if (encode)
deinterleave_vector(X, N_B, spread);
haar1(X, N_B0, spread0);
if (lowband)
deinterleave_vector(lowband, N_B, spread);
haar1(lowband, N_B0, spread0);
spread0 = spread;
}
if (encode)
deinterleave_vector(X, N_B, spread0);
if (lowband)
deinterleave_vector(lowband, N_B, spread0);
}
/* If we need more than 32 bits, try splitting the band in two. */
@ -752,6 +779,12 @@ static void quant_band(int encode, const CELTMode *m, int i, celt_norm *X, celt_
interleave_vector(X, N_B, spread0);
if (lowband)
interleave_vector(lowband, N_B, spread0);
if (do_haar)
{
haar1(X, N_B0, spread0>>1);
if (lowband)
haar1(lowband, N_B0, spread0>>1);
}
}
if (lowband_out && !stereo)