diff --git a/libavutil/tx.c b/libavutil/tx.c index 05d4de30cc..6d0e854084 100644 --- a/libavutil/tx.c +++ b/libavutil/tx.c @@ -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)) diff --git a/libavutil/tx_priv.h b/libavutil/tx_priv.h index 1d4245e71b..b889f6d3b4 100644 --- a/libavutil/tx_priv.h +++ b/libavutil/tx_priv.h @@ -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,