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/*
* 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;
}
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