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lavu/tx: add parity revtab generator version

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This will be used for SIMD support.
This commit is contained in:
Lynne 2021-04-10 03:52:31 +02:00
parent 18af1ea8d1
commit ff71671d88
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GPG Key ID: A2FEA5F03F034464
2 changed files with 80 additions and 0 deletions
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49
libavutil/tx.c
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@ -158,6 +158,55 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s)
return 0;
}
static void parity_revtab_generator(int *revtab, int n, int inv, int offset,
int is_dual, int dual_high, int len,
int basis, int dual_stride)
{
len >>= 1;
if (len <= basis) {
int k1, k2, *even, *odd, stride;
is_dual = is_dual && dual_stride;
dual_high = is_dual & dual_high;
stride = is_dual ? FFMIN(dual_stride, len) : 0;
even = &revtab[offset + dual_high*(stride - 2*len)];
odd = &even[len + (is_dual && !dual_high)*len + dual_high*len];
for (int i = 0; i < len; i++) {
k1 = -split_radix_permutation(offset + i*2 + 0, n, inv) & (n - 1);
k2 = -split_radix_permutation(offset + i*2 + 1, n, inv) & (n - 1);
*even++ = k1;
*odd++ = k2;
if (stride && !((i + 1) % stride)) {
even += stride;
odd += stride;
}
}
return;
}
parity_revtab_generator(revtab, n, inv, offset,
0, 0, len >> 0, basis, dual_stride);
parity_revtab_generator(revtab, n, inv, offset + (len >> 0),
1, 0, len >> 1, basis, dual_stride);
parity_revtab_generator(revtab, n, inv, offset + (len >> 0) + (len >> 1),
1, 1, len >> 1, basis, dual_stride);
}
void ff_tx_gen_split_radix_parity_revtab(int *revtab, int len, int inv,
int basis, int dual_stride)
{
basis >>= 1;
if (len < basis)
return;
av_assert0(!dual_stride || !(dual_stride & (dual_stride - 1)));
av_assert0(dual_stride <= basis);
parity_revtab_generator(revtab, len, inv, 0, 0, 0, len, basis, dual_stride);
}
av_cold void av_tx_uninit(AVTXContext **ctx)
{
if (!(*ctx))

31
libavutil/tx_priv.h
View File

@ -149,6 +149,37 @@ int ff_tx_gen_ptwo_revtab(AVTXContext *s, int invert_lookup);
*/
int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s);
/*
* This generates a parity-based revtab of length len and direction inv.
*
* Parity means even and odd complex numbers will be split, e.g. the even
* coefficients will come first, after which the odd coefficients will be
* placed. For example, a 4-point transform's coefficients after reordering:
* z[0].re, z[0].im, z[2].re, z[2].im, z[1].re, z[1].im, z[3].re, z[3].im
*
* The basis argument is the length of the largest non-composite transform
* supported, and also implies that the basis/2 transform is supported as well,
* as the split-radix algorithm requires it to be.
*
* The dual_stride argument indicates that both the basis, as well as the
* basis/2 transforms support doing two transforms at once, and the coefficients
* will be interleaved between each pair in a split-radix like so (stride == 2):
* tx1[0], tx1[2], tx2[0], tx2[2], tx1[1], tx1[3], tx2[1], tx2[3]
* A non-zero number switches this on, with the value indicating the stride
* (how many values of 1 transform to put first before switching to the other).
* Must be a power of two or 0. Must be less than the basis.
* Value will be clipped to the transform size, so for a basis of 16 and a
* dual_stride of 8, dual 8-point transforms will be laid out as if dual_stride
* was set to 4.
* Usually you'll set this to half the complex numbers that fit in a single
* register or 0. This allows to reuse SSE functions as dual-transform
* functions in AVX mode.
*
* If length is smaller than basis/2 this function will not do anything.
*/
void ff_tx_gen_split_radix_parity_revtab(int *revtab, int len, int inv,
int basis, int dual_stride);
/* Templated init functions */
int ff_tx_init_mdct_fft_float(AVTXContext *s, av_tx_fn *tx,
enum AVTXType type, int inv, int len,