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226 lines
5.4 KiB
C
Executable File
226 lines
5.4 KiB
C
Executable File
/*
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* (I)DCT Transforms
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* Copyright (c) 2009 Peter Ross <pross@xvid.org>
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* Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
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* Copyright (c) 2010 Vitor Sessak
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* (Inverse) Discrete Cosine Transforms. These are also known as the
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* type II and type III DCTs respectively.
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*/
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#include <math.h>
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#include <string.h>
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#include "libavutil/mathematics.h"
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#include "dct.h"
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#include "dct32.h"
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/* sin((M_PI * x / (2 * n)) */
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#define SIN(s, n, x) (s->costab[(n) - (x)])
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/* cos((M_PI * x / (2 * n)) */
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#define COS(s, n, x) (s->costab[x])
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static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
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{
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int n = 1 << ctx->nbits;
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int i;
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data[0] = 0;
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for (i = 1; i < n / 2; i++) {
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float tmp1 = data[i ];
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float tmp2 = data[n - i];
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float s = SIN(ctx, n, 2 * i);
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s *= tmp1 + tmp2;
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tmp1 = (tmp1 - tmp2) * 0.5f;
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data[i] = s + tmp1;
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data[n - i] = s - tmp1;
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}
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data[n / 2] *= 2;
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ctx->rdft.rdft_calc(&ctx->rdft, data);
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data[0] *= 0.5f;
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for (i = 1; i < n - 2; i += 2) {
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data[i + 1] += data[i - 1];
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data[i] = -data[i + 2];
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}
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data[n - 1] = 0;
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}
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static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
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{
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int n = 1 << ctx->nbits;
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int i;
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float next = -0.5f * (data[0] - data[n]);
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for (i = 0; i < n / 2; i++) {
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float tmp1 = data[i];
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float tmp2 = data[n - i];
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float s = SIN(ctx, n, 2 * i);
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float c = COS(ctx, n, 2 * i);
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c *= tmp1 - tmp2;
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s *= tmp1 - tmp2;
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next += c;
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tmp1 = (tmp1 + tmp2) * 0.5f;
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data[i] = tmp1 - s;
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data[n - i] = tmp1 + s;
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}
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ctx->rdft.rdft_calc(&ctx->rdft, data);
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data[n] = data[1];
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data[1] = next;
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for (i = 3; i <= n; i += 2)
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data[i] = data[i - 2] - data[i];
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}
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static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
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{
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int n = 1 << ctx->nbits;
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int i;
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float next = data[n - 1];
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float inv_n = 1.0f / n;
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for (i = n - 2; i >= 2; i -= 2) {
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float val1 = data[i];
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float val2 = data[i - 1] - data[i + 1];
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float c = COS(ctx, n, i);
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float s = SIN(ctx, n, i);
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data[i] = c * val1 + s * val2;
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data[i + 1] = s * val1 - c * val2;
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}
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data[1] = 2 * next;
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ctx->rdft.rdft_calc(&ctx->rdft, data);
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for (i = 0; i < n / 2; i++) {
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float tmp1 = data[i] * inv_n;
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float tmp2 = data[n - i - 1] * inv_n;
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float csc = ctx->csc2[i] * (tmp1 - tmp2);
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tmp1 += tmp2;
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data[i] = tmp1 + csc;
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data[n - i - 1] = tmp1 - csc;
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}
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}
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static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
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{
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int n = 1 << ctx->nbits;
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int i;
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float next;
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for (i = 0; i < n / 2; i++) {
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float tmp1 = data[i];
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float tmp2 = data[n - i - 1];
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float s = SIN(ctx, n, 2 * i + 1);
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s *= tmp1 - tmp2;
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tmp1 = (tmp1 + tmp2) * 0.5f;
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data[i] = tmp1 + s;
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data[n-i-1] = tmp1 - s;
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}
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ctx->rdft.rdft_calc(&ctx->rdft, data);
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next = data[1] * 0.5;
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data[1] *= -1;
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for (i = n - 2; i >= 0; i -= 2) {
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float inr = data[i ];
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float ini = data[i + 1];
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float c = COS(ctx, n, i);
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float s = SIN(ctx, n, i);
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data[i] = c * inr + s * ini;
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data[i + 1] = next;
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next += s * inr - c * ini;
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}
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}
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static void dct32_func(DCTContext *ctx, FFTSample *data)
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{
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ctx->dct32(data, data);
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}
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av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
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{
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int n = 1 << nbits;
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int i;
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int ret;
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memset(s, 0, sizeof(*s));
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s->nbits = nbits;
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s->inverse = inverse;
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if (inverse == DCT_II && nbits == 5) {
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s->dct_calc = dct32_func;
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} else {
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ff_init_ff_cos_tabs(nbits + 2);
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s->costab = ff_cos_tabs[nbits + 2];
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s->csc2 = av_malloc_array(n / 2, sizeof(FFTSample));
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if (!s->csc2)
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return AVERROR(ENOMEM);
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if ((ret = ff_rdft_init(&s->rdft, nbits, inverse == DCT_III)) < 0) {
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av_freep(&s->csc2);
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return ret;
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}
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for (i = 0; i < n / 2; i++)
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s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
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switch (inverse) {
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case DCT_I : s->dct_calc = dct_calc_I_c; break;
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case DCT_II : s->dct_calc = dct_calc_II_c; break;
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case DCT_III: s->dct_calc = dct_calc_III_c; break;
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case DST_I : s->dct_calc = dst_calc_I_c; break;
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}
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}
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s->dct32 = ff_dct32_float;
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if (ARCH_X86)
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ff_dct_init_x86(s);
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return 0;
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}
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av_cold void ff_dct_end(DCTContext *s)
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{
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ff_rdft_end(&s->rdft);
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av_freep(&s->csc2);
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}
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