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libavcodec/lpc.c

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00001 
00022 #include "libavutil/lls.h"
00023 
00024 #define LPC_USE_DOUBLE
00025 #include "lpc.h"
00026 
00027 
00031 static void lpc_apply_welch_window_c(const int32_t *data, int len,
00032                                      double *w_data)
00033 {
00034     int i, n2;
00035     double w;
00036     double c;
00037 
00038     assert(!(len&1)); //the optimization in r11881 does not support odd len
00039                       //if someone wants odd len extend the change in r11881
00040 
00041     n2 = (len >> 1);
00042     c = 2.0 / (len - 1.0);
00043 
00044     w_data+=n2;
00045       data+=n2;
00046     for(i=0; i<n2; i++) {
00047         w = c - n2 + i;
00048         w = 1.0 - (w * w);
00049         w_data[-i-1] = data[-i-1] * w;
00050         w_data[+i  ] = data[+i  ] * w;
00051     }
00052 }
00053 
00058 static void lpc_compute_autocorr_c(const double *data, int len, int lag,
00059                                    double *autoc)
00060 {
00061     int i, j;
00062 
00063     for(j=0; j<lag; j+=2){
00064         double sum0 = 1.0, sum1 = 1.0;
00065         for(i=j; i<len; i++){
00066             sum0 += data[i] * data[i-j];
00067             sum1 += data[i] * data[i-j-1];
00068         }
00069         autoc[j  ] = sum0;
00070         autoc[j+1] = sum1;
00071     }
00072 
00073     if(j==lag){
00074         double sum = 1.0;
00075         for(i=j-1; i<len; i+=2){
00076             sum += data[i  ] * data[i-j  ]
00077                  + data[i+1] * data[i-j+1];
00078         }
00079         autoc[j] = sum;
00080     }
00081 }
00082 
00086 static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
00087                                int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
00088 {
00089     int i;
00090     double cmax, error;
00091     int32_t qmax;
00092     int sh;
00093 
00094     /* define maximum levels */
00095     qmax = (1 << (precision - 1)) - 1;
00096 
00097     /* find maximum coefficient value */
00098     cmax = 0.0;
00099     for(i=0; i<order; i++) {
00100         cmax= FFMAX(cmax, fabs(lpc_in[i]));
00101     }
00102 
00103     /* if maximum value quantizes to zero, return all zeros */
00104     if(cmax * (1 << max_shift) < 1.0) {
00105         *shift = zero_shift;
00106         memset(lpc_out, 0, sizeof(int32_t) * order);
00107         return;
00108     }
00109 
00110     /* calculate level shift which scales max coeff to available bits */
00111     sh = max_shift;
00112     while((cmax * (1 << sh) > qmax) && (sh > 0)) {
00113         sh--;
00114     }
00115 
00116     /* since negative shift values are unsupported in decoder, scale down
00117        coefficients instead */
00118     if(sh == 0 && cmax > qmax) {
00119         double scale = ((double)qmax) / cmax;
00120         for(i=0; i<order; i++) {
00121             lpc_in[i] *= scale;
00122         }
00123     }
00124 
00125     /* output quantized coefficients and level shift */
00126     error=0;
00127     for(i=0; i<order; i++) {
00128         error -= lpc_in[i] * (1 << sh);
00129         lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
00130         error -= lpc_out[i];
00131     }
00132     *shift = sh;
00133 }
00134 
00135 static int estimate_best_order(double *ref, int min_order, int max_order)
00136 {
00137     int i, est;
00138 
00139     est = min_order;
00140     for(i=max_order-1; i>=min_order-1; i--) {
00141         if(ref[i] > 0.10) {
00142             est = i+1;
00143             break;
00144         }
00145     }
00146     return est;
00147 }
00148 
00157 int ff_lpc_calc_coefs(LPCContext *s,
00158                       const int32_t *samples, int blocksize, int min_order,
00159                       int max_order, int precision,
00160                       int32_t coefs[][MAX_LPC_ORDER], int *shift,
00161                       enum FFLPCType lpc_type, int lpc_passes,
00162                       int omethod, int max_shift, int zero_shift)
00163 {
00164     double autoc[MAX_LPC_ORDER+1];
00165     double ref[MAX_LPC_ORDER];
00166     double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
00167     int i, j, pass;
00168     int opt_order;
00169 
00170     assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
00171            lpc_type > FF_LPC_TYPE_FIXED);
00172 
00173     /* reinit LPC context if parameters have changed */
00174     if (blocksize != s->blocksize || max_order != s->max_order ||
00175         lpc_type  != s->lpc_type) {
00176         ff_lpc_end(s);
00177         ff_lpc_init(s, blocksize, max_order, lpc_type);
00178     }
00179 
00180     if (lpc_type == FF_LPC_TYPE_LEVINSON) {
00181         double *windowed_samples = s->windowed_samples + max_order;
00182 
00183         s->lpc_apply_welch_window(samples, blocksize, windowed_samples);
00184 
00185         s->lpc_compute_autocorr(windowed_samples, blocksize, max_order, autoc);
00186 
00187         compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
00188 
00189         for(i=0; i<max_order; i++)
00190             ref[i] = fabs(lpc[i][i]);
00191     } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
00192         LLSModel m[2];
00193         double var[MAX_LPC_ORDER+1], av_uninit(weight);
00194 
00195         for(pass=0; pass<lpc_passes; pass++){
00196             av_init_lls(&m[pass&1], max_order);
00197 
00198             weight=0;
00199             for(i=max_order; i<blocksize; i++){
00200                 for(j=0; j<=max_order; j++)
00201                     var[j]= samples[i-j];
00202 
00203                 if(pass){
00204                     double eval, inv, rinv;
00205                     eval= av_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
00206                     eval= (512>>pass) + fabs(eval - var[0]);
00207                     inv = 1/eval;
00208                     rinv = sqrt(inv);
00209                     for(j=0; j<=max_order; j++)
00210                         var[j] *= rinv;
00211                     weight += inv;
00212                 }else
00213                     weight++;
00214 
00215                 av_update_lls(&m[pass&1], var, 1.0);
00216             }
00217             av_solve_lls(&m[pass&1], 0.001, 0);
00218         }
00219 
00220         for(i=0; i<max_order; i++){
00221             for(j=0; j<max_order; j++)
00222                 lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
00223             ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
00224         }
00225         for(i=max_order-1; i>0; i--)
00226             ref[i] = ref[i-1] - ref[i];
00227     }
00228     opt_order = max_order;
00229 
00230     if(omethod == ORDER_METHOD_EST) {
00231         opt_order = estimate_best_order(ref, min_order, max_order);
00232         i = opt_order-1;
00233         quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
00234     } else {
00235         for(i=min_order-1; i<max_order; i++) {
00236             quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
00237         }
00238     }
00239 
00240     return opt_order;
00241 }
00242 
00243 av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
00244                         enum FFLPCType lpc_type)
00245 {
00246     s->blocksize = blocksize;
00247     s->max_order = max_order;
00248     s->lpc_type  = lpc_type;
00249 
00250     if (lpc_type == FF_LPC_TYPE_LEVINSON) {
00251         s->windowed_samples = av_mallocz((blocksize + max_order + 2) *
00252                                          sizeof(*s->windowed_samples));
00253         if (!s->windowed_samples)
00254             return AVERROR(ENOMEM);
00255     } else {
00256         s->windowed_samples = NULL;
00257     }
00258 
00259     s->lpc_apply_welch_window = lpc_apply_welch_window_c;
00260     s->lpc_compute_autocorr   = lpc_compute_autocorr_c;
00261 
00262     if (HAVE_MMX)
00263         ff_lpc_init_x86(s);
00264 
00265     return 0;
00266 }
00267 
00268 av_cold void ff_lpc_end(LPCContext *s)
00269 {
00270     av_freep(&s->windowed_samples);
00271 }

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