FFmpeg/libavutil/tx.c
Lynne 42e2319ba9 lavu/tx: add support for double precision FFT and MDCT
Simply moves and templates the actual transforms to support an
additional data type.
Unlike the float version, which is equal or better than libfftw3f,
double precision output is bit identical with libfftw3.
2019-08-02 01:19:52 +01:00

145 lines
3.9 KiB
C

/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "tx_priv.h"
/* Calculates the modular multiplicative inverse, not fast, replace */
static av_always_inline int mulinv(int n, int m)
{
n = n % m;
for (int x = 1; x < m; x++)
if (((n * x) % m) == 1)
return x;
av_assert0(0); /* Never reached */
}
/* Guaranteed to work for any n, m where gcd(n, m) == 1 */
int ff_tx_gen_compound_mapping(AVTXContext *s)
{
int *in_map, *out_map;
const int n = s->n;
const int m = s->m;
const int inv = s->inv;
const int type = s->type;
const int len = n*m;
const int m_inv = mulinv(m, n);
const int n_inv = mulinv(n, m);
const int mdct = type == AV_TX_FLOAT_MDCT || type == AV_TX_DOUBLE_MDCT;
if (!(s->pfatab = av_malloc(2*len*sizeof(*s->pfatab))))
return AVERROR(ENOMEM);
in_map = s->pfatab;
out_map = s->pfatab + n*m;
/* Ruritanian map for input, CRT map for output, can be swapped */
for (int j = 0; j < m; j++) {
for (int i = 0; i < n; i++) {
/* Shifted by 1 to simplify MDCTs */
in_map[j*n + i] = ((i*m + j*n) % len) << mdct;
out_map[(i*m*m_inv + j*n*n_inv) % len] = i*m + j;
}
}
/* Change transform direction by reversing all ACs */
if (inv) {
for (int i = 0; i < m; i++) {
int *in = &in_map[i*n + 1]; /* Skip the DC */
for (int j = 0; j < ((n - 1) >> 1); j++)
FFSWAP(int, in[j], in[n - j - 2]);
}
}
/* Our 15-point transform is also a compound one, so embed its input map */
if (n == 15) {
for (int k = 0; k < m; k++) {
int tmp[15];
memcpy(tmp, &in_map[k*15], 15*sizeof(*tmp));
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 3; j++)
in_map[k*15 + i*3 + j] = tmp[(i*3 + j*5) % 15];
}
}
}
return 0;
}
int ff_tx_gen_ptwo_revtab(AVTXContext *s)
{
const int m = s->m, inv = s->inv;
if (!(s->revtab = av_malloc(m*sizeof(*s->revtab))))
return AVERROR(ENOMEM);
/* Default */
for (int i = 0; i < m; i++) {
int k = -split_radix_permutation(i, m, inv) & (m - 1);
s->revtab[k] = i;
}
return 0;
}
av_cold void av_tx_uninit(AVTXContext **ctx)
{
if (!(*ctx))
return;
av_free((*ctx)->pfatab);
av_free((*ctx)->exptab);
av_free((*ctx)->revtab);
av_free((*ctx)->tmp);
av_freep(ctx);
}
av_cold int av_tx_init(AVTXContext **ctx, av_tx_fn *tx, enum AVTXType type,
int inv, int len, const void *scale, uint64_t flags)
{
int err;
AVTXContext *s = av_mallocz(sizeof(*s));
if (!s)
return AVERROR(ENOMEM);
switch (type) {
case AV_TX_FLOAT_FFT:
case AV_TX_FLOAT_MDCT:
if ((err = ff_tx_init_mdct_fft_float(s, tx, type, inv, len, scale, flags)))
goto fail;
break;
case AV_TX_DOUBLE_FFT:
case AV_TX_DOUBLE_MDCT:
if ((err = ff_tx_init_mdct_fft_double(s, tx, type, inv, len, scale, flags)))
goto fail;
break;
default:
err = AVERROR(EINVAL);
goto fail;
}
*ctx = s;
return 0;
fail:
av_tx_uninit(&s);
*tx = NULL;
return err;
}