Libav 0.7.1
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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 Libav. 00008 * 00009 * Libav 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 * Libav 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 Libav; 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 }