/*
* (I)DCT Transforms
* Copyright (c) 2009 Peter Ross <pross@xvid.org>
* Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
* Copyright (c) 2010 Vitor Sessak
*
* 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 St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* (Inverse) Discrete Cosine Transforms. These are also known as the
* type II and type III DCTs respectively.
*/
#include <math.h>
#include <string.h>
#include "libavutil/mathematics.h"
#include "dct.h"
#include "dct32.h"
/* sin((M_PI * x / (2 * n)) */
#define SIN(s, n, x) (s->costab[(n) - (x)])
/* cos((M_PI * x / (2 * n)) */
#define COS(s, n, x) (s->costab[x])
static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
{
int n = 1 << ctx->nbits;
int i;
data[0] = 0;
for (i = 1; i < n / 2; i++) {
float tmp1 = data[i ];
float tmp2 = data[n - i];
float s = SIN(ctx, n, 2 * i);
s *= tmp1 + tmp2;
tmp1 = (tmp1 - tmp2) * 0.5f;
data[i] = s + tmp1;
data[n - i] = s - tmp1;
}
data[n / 2] *= 2;
ctx->rdft.rdft_calc(&ctx->rdft, data);
data[0] *= 0.5f;
for (i = 1; i < n - 2; i += 2) {
data[i + 1] += data[i - 1];
data[i] = -data[i + 2];
}
data[n - 1] = 0;
}
static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
{
int n = 1 << ctx->nbits;
int i;
float next = -0.5f * (data[0] - data[n]);
for (i = 0; i < n / 2; i++) {
float tmp1 = data[i];
float tmp2 = data[n - i];
float s = SIN(ctx, n, 2 * i);
float c = COS(ctx, n, 2 * i);
c *= tmp1 - tmp2;
s *= tmp1 - tmp2;
next += c;
tmp1 = (tmp1 + tmp2) * 0.5f;
data[i] = tmp1 - s;
data[n - i] = tmp1 + s;
}
ctx->rdft.rdft_calc(&ctx->rdft, data);
data[n] = data[1];
data[1] = next;
for (i = 3; i <= n; i += 2)
data[i] = data[i - 2] - data[i];
}
static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
{
int n = 1 << ctx->nbits;
int i;
float next = data[n - 1];
float inv_n = 1.0f / n;
for (i = n - 2; i >= 2; i -= 2) {
float val1 = data[i];
float val2 = data[i - 1] - data[i + 1];
float c = COS(ctx, n, i);
float s = SIN(ctx, n, i);
data[i] = c * val1 + s * val2;
data[i + 1] = s * val1 - c * val2;
}
data[1] = 2 * next;
ctx->rdft.rdft_calc(&ctx->rdft, data);
for (i = 0; i < n / 2; i++) {
float tmp1 = data[i] * inv_n;
float tmp2 = data[n - i - 1] * inv_n;
float csc = ctx->csc2[i] * (tmp1 - tmp2);
tmp1 += tmp2;
data[i] = tmp1 + csc;
data[n - i - 1] = tmp1 - csc;
}
}
static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
{
int n = 1 << ctx->nbits;
int i;
float next;
for (i = 0; i < n / 2; i++) {
float tmp1 = data[i];
float tmp2 = data[n - i - 1];
float s = SIN(ctx, n, 2 * i + 1);
s *= tmp1 - tmp2;
tmp1 = (tmp1 + tmp2) * 0.5f;
data[i] = tmp1 + s;
data[n-i-1] = tmp1 - s;
}
ctx->rdft.rdft_calc(&ctx->rdft, data);
next = data[1] * 0.5;
data[1] *= -1;
for (i = n - 2; i >= 0; i -= 2) {
float inr = data[i ];
float ini = data[i + 1];
float c = COS(ctx, n, i);
float s = SIN(ctx, n, i);
data[i] = c * inr + s * ini;
data[i + 1] = next;
next += s * inr - c * ini;
}
}
static void dct32_func(DCTContext *ctx, FFTSample *data)
{
ctx->dct32(data, data);
}
av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
{
int n = 1 << nbits;
int i;
s->nbits = nbits;
s->inverse = inverse;
if (inverse == DCT_II && nbits == 5) {
s->dct_calc = dct32_func;
} else {
ff_init_ff_cos_tabs(nbits + 2);
s->costab = ff_cos_tabs[nbits + 2];
s->csc2 = av_malloc(n / 2 * sizeof(FFTSample));
if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
av_free(s->csc2);
return -1;
}
for (i = 0; i < n / 2; i++)
s
->csc2
[i
] = 0.5 / sin((M_PI
/ (2 * n
) * (2 * i
+ 1)));
switch (inverse) {
case DCT_I : s->dct_calc = dct_calc_I_c; break;
case DCT_II : s->dct_calc = dct_calc_II_c; break;
case DCT_III: s->dct_calc = dct_calc_III_c; break;
case DST_I : s->dct_calc = dst_calc_I_c; break;
}
}
s->dct32 = ff_dct32_float;
if (ARCH_X86)
ff_dct_init_x86(s);
return 0;
}
av_cold void ff_dct_end(DCTContext *s)
{
ff_rdft_end(&s->rdft);
av_free(s->csc2);
}