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libavcodec/dct.c

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00001 /*
00002  * (I)DCT Transforms
00003  * Copyright (c) 2009 Peter Ross <pross@xvid.org>
00004  * Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
00005  * Copyright (c) 2010 Vitor Sessak
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
00022  */
00023 
00030 #include <math.h>
00031 #include "libavutil/mathematics.h"
00032 #include "dct.h"
00033 #include "dct32.h"
00034 
00035 /* sin((M_PI * x / (2*n)) */
00036 #define SIN(s,n,x) (s->costab[(n) - (x)])
00037 
00038 /* cos((M_PI * x / (2*n)) */
00039 #define COS(s,n,x) (s->costab[x])
00040 
00041 static void ff_dst_calc_I_c(DCTContext *ctx, FFTSample *data)
00042 {
00043     int n = 1 << ctx->nbits;
00044     int i;
00045 
00046     data[0] = 0;
00047     for(i = 1; i < n/2; i++) {
00048         float tmp1 = data[i    ];
00049         float tmp2 = data[n - i];
00050         float s = SIN(ctx, n, 2*i);
00051 
00052         s *= tmp1 + tmp2;
00053         tmp1 = (tmp1 - tmp2) * 0.5f;
00054         data[i    ] = s + tmp1;
00055         data[n - i] = s - tmp1;
00056     }
00057 
00058     data[n/2] *= 2;
00059     ctx->rdft.rdft_calc(&ctx->rdft, data);
00060 
00061     data[0] *= 0.5f;
00062 
00063     for(i = 1; i < n-2; i += 2) {
00064         data[i + 1] += data[i - 1];
00065         data[i    ] = -data[i + 2];
00066     }
00067 
00068     data[n-1] = 0;
00069 }
00070 
00071 static void ff_dct_calc_I_c(DCTContext *ctx, FFTSample *data)
00072 {
00073     int n = 1 << ctx->nbits;
00074     int i;
00075     float next = -0.5f * (data[0] - data[n]);
00076 
00077     for(i = 0; i < n/2; i++) {
00078         float tmp1 = data[i    ];
00079         float tmp2 = data[n - i];
00080         float s = SIN(ctx, n, 2*i);
00081         float c = COS(ctx, n, 2*i);
00082 
00083         c *= tmp1 - tmp2;
00084         s *= tmp1 - tmp2;
00085 
00086         next += c;
00087 
00088         tmp1 = (tmp1 + tmp2) * 0.5f;
00089         data[i    ] = tmp1 - s;
00090         data[n - i] = tmp1 + s;
00091     }
00092 
00093     ctx->rdft.rdft_calc(&ctx->rdft, data);
00094     data[n] = data[1];
00095     data[1] = next;
00096 
00097     for(i = 3; i <= n; i += 2)
00098         data[i] = data[i - 2] - data[i];
00099 }
00100 
00101 static void ff_dct_calc_III_c(DCTContext *ctx, FFTSample *data)
00102 {
00103     int n = 1 << ctx->nbits;
00104     int i;
00105 
00106     float next = data[n - 1];
00107     float inv_n = 1.0f / n;
00108 
00109     for (i = n - 2; i >= 2; i -= 2) {
00110         float val1 = data[i    ];
00111         float val2 = data[i - 1] - data[i + 1];
00112         float c = COS(ctx, n, i);
00113         float s = SIN(ctx, n, i);
00114 
00115         data[i    ] = c * val1 + s * val2;
00116         data[i + 1] = s * val1 - c * val2;
00117     }
00118 
00119     data[1] = 2 * next;
00120 
00121     ctx->rdft.rdft_calc(&ctx->rdft, data);
00122 
00123     for (i = 0; i < n / 2; i++) {
00124         float tmp1 = data[i        ] * inv_n;
00125         float tmp2 = data[n - i - 1] * inv_n;
00126         float csc = ctx->csc2[i] * (tmp1 - tmp2);
00127 
00128         tmp1 += tmp2;
00129         data[i        ] = tmp1 + csc;
00130         data[n - i - 1] = tmp1 - csc;
00131     }
00132 }
00133 
00134 static void ff_dct_calc_II_c(DCTContext *ctx, FFTSample *data)
00135 {
00136     int n = 1 << ctx->nbits;
00137     int i;
00138     float next;
00139 
00140     for (i=0; i < n/2; i++) {
00141         float tmp1 = data[i        ];
00142         float tmp2 = data[n - i - 1];
00143         float s = SIN(ctx, n, 2*i + 1);
00144 
00145         s *= tmp1 - tmp2;
00146         tmp1 = (tmp1 + tmp2) * 0.5f;
00147 
00148         data[i    ] = tmp1 + s;
00149         data[n-i-1] = tmp1 - s;
00150     }
00151 
00152     ctx->rdft.rdft_calc(&ctx->rdft, data);
00153 
00154     next = data[1] * 0.5;
00155     data[1] *= -1;
00156 
00157     for (i = n - 2; i >= 0; i -= 2) {
00158         float inr = data[i    ];
00159         float ini = data[i + 1];
00160         float c = COS(ctx, n, i);
00161         float s = SIN(ctx, n, i);
00162 
00163         data[i  ] = c * inr + s * ini;
00164 
00165         data[i+1] = next;
00166 
00167         next +=     s * inr - c * ini;
00168     }
00169 }
00170 
00171 static void dct32_func(DCTContext *ctx, FFTSample *data)
00172 {
00173     ctx->dct32(data, data);
00174 }
00175 
00176 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
00177 {
00178     int n = 1 << nbits;
00179     int i;
00180 
00181     memset(s, 0, sizeof(*s));
00182 
00183     s->nbits    = nbits;
00184     s->inverse  = inverse;
00185 
00186     if (inverse == DCT_II && nbits == 5) {
00187         s->dct_calc = dct32_func;
00188     } else {
00189         ff_init_ff_cos_tabs(nbits+2);
00190 
00191         s->costab = ff_cos_tabs[nbits+2];
00192 
00193         s->csc2 = av_malloc(n/2 * sizeof(FFTSample));
00194 
00195         if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
00196             av_free(s->csc2);
00197             return -1;
00198         }
00199 
00200         for (i = 0; i < n/2; i++)
00201             s->csc2[i] = 0.5 / sin((M_PI / (2*n) * (2*i + 1)));
00202 
00203         switch(inverse) {
00204         case DCT_I  : s->dct_calc = ff_dct_calc_I_c; break;
00205         case DCT_II : s->dct_calc = ff_dct_calc_II_c ; break;
00206         case DCT_III: s->dct_calc = ff_dct_calc_III_c; break;
00207         case DST_I  : s->dct_calc = ff_dst_calc_I_c; break;
00208         }
00209     }
00210 
00211     s->dct32 = ff_dct32_float;
00212     if (HAVE_MMX)     ff_dct_init_mmx(s);
00213 
00214     return 0;
00215 }
00216 
00217 av_cold void ff_dct_end(DCTContext *s)
00218 {
00219     ff_rdft_end(&s->rdft);
00220     av_free(s->csc2);
00221 }

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