0,0 → 1,222 |
/* |
* (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> |
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#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)]) |
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/* cos((M_PI * x / (2 * n)) */ |
#define COS(s, n, x) (s->costab[x]) |
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static void dst_calc_I_c(DCTContext *ctx, FFTSample *data) |
{ |
int n = 1 << ctx->nbits; |
int i; |
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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); |
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s *= tmp1 + tmp2; |
tmp1 = (tmp1 - tmp2) * 0.5f; |
data[i] = s + tmp1; |
data[n - i] = s - tmp1; |
} |
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data[n / 2] *= 2; |
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) { |
data[i + 1] += data[i - 1]; |
data[i] = -data[i + 2]; |
} |
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data[n - 1] = 0; |
} |
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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); |
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c *= tmp1 - tmp2; |
s *= tmp1 - tmp2; |
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next += c; |
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tmp1 = (tmp1 + tmp2) * 0.5f; |
data[i] = tmp1 - s; |
data[n - i] = tmp1 + s; |
} |
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ctx->rdft.rdft_calc(&ctx->rdft, data); |
data[n] = data[1]; |
data[1] = next; |
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for (i = 3; i <= n; i += 2) |
data[i] = data[i - 2] - data[i]; |
} |
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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; |
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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); |
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data[i] = c * val1 + s * val2; |
data[i + 1] = s * val1 - c * val2; |
} |
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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++) { |
float tmp1 = data[i] * inv_n; |
float tmp2 = data[n - i - 1] * inv_n; |
float csc = ctx->csc2[i] * (tmp1 - tmp2); |
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tmp1 += tmp2; |
data[i] = tmp1 + csc; |
data[n - i - 1] = tmp1 - csc; |
} |
} |
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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; |
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data[i] = tmp1 + s; |
data[n-i-1] = tmp1 - s; |
} |
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ctx->rdft.rdft_calc(&ctx->rdft, data); |
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next = data[1] * 0.5; |
data[1] *= -1; |
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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); |
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data[i] = c * inr + s * ini; |
data[i + 1] = next; |
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next += s * inr - c * ini; |
} |
} |
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static void dct32_func(DCTContext *ctx, FFTSample *data) |
{ |
ctx->dct32(data, data); |
} |
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av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse) |
{ |
int n = 1 << nbits; |
int i; |
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memset(s, 0, sizeof(*s)); |
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s->nbits = nbits; |
s->inverse = inverse; |
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if (inverse == DCT_II && nbits == 5) { |
s->dct_calc = dct32_func; |
} else { |
ff_init_ff_cos_tabs(nbits + 2); |
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s->costab = ff_cos_tabs[nbits + 2]; |
s->csc2 = av_malloc(n / 2 * sizeof(FFTSample)); |
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if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) { |
av_free(s->csc2); |
return -1; |
} |
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for (i = 0; i < n / 2; i++) |
s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1))); |
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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; |
} |
} |
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s->dct32 = ff_dct32_float; |
if (ARCH_X86) |
ff_dct_init_x86(s); |
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return 0; |
} |
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av_cold void ff_dct_end(DCTContext *s) |
{ |
ff_rdft_end(&s->rdft); |
av_free(s->csc2); |
} |