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/*

 * (I)DCT Transforms

 * Copyright (c) 2009 Peter Ross 

 * Copyright (c) 2010 Alex Converse 

 * 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 

#include 

#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;

    memset(s, 0, sizeof(*s));

    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);

}