static int build_filter(ResampleContext *c, void *filter, double factor, int tap_count, int alloc, int phase_count, int scale, int filter_type, double kaiser_beta){ int ph, i; double x, y, w, t, s; double *tab = av_malloc_array(tap_count+1, sizeof(*tab)); double *sin_lut = av_malloc_array(phase_count / 2 + 1, sizeof(*sin_lut)); const int center= (tap_count-1)/2; if (!tab || !sin_lut) goto fail; /* if upsampling, only need to interpolate, no filter */ if (factor > 1.0) factor = 1.0; av_assert0(phase_count == 1 || phase_count % 2 == 0); if (factor == 1.0) { for (ph = 0; ph <= phase_count / 2; ph++) sin_lut[ph] = sin(M_PI * ph / phase_count); } for(ph = 0; ph <= phase_count / 2; ph++) { double norm = 0; s = sin_lut[ph]; for(i=0;i<=tap_count;i++) { x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor; if (x == 0) y = 1.0; else if (factor == 1.0) y = s / x; else y = sin(x) / x; switch(filter_type){ case SWR_FILTER_TYPE_CUBIC:{ const float d= -0.5; //first order derivative = -0.5 x = fabs(((double)(i - center) - (double)ph / phase_count) * factor); if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*( -x*x + x*x*x); else y= d*(-4 + 8*x - 5*x*x + x*x*x); break;} case SWR_FILTER_TYPE_BLACKMAN_NUTTALL: w = 2.0*x / (factor*tap_count); t = -cos(w); y *= 0.3635819 - 0.4891775 * t + 0.1365995 * (2*t*t-1) - 0.0106411 * (4*t*t*t - 3*t); break; case SWR_FILTER_TYPE_KAISER: w = 2.0*x / (factor*tap_count*M_PI); y *= bessel(kaiser_beta*sqrt(FFMAX(1-w*w, 0))); break; default: av_assert0(0); } tab[i] = y; s = -s; if (i < tap_count) norm += y; } /* normalize so that an uniform color remains the same */ switch(c->format){ case AV_SAMPLE_FMT_S16P: for(i=0;i<tap_count;i++) ((int16_t*)filter)[ph * alloc + i] = av_clip_int16(lrintf(tab[i] * scale / norm)); if (tap_count % 2 == 0) { for (i = 0; i < tap_count; i++) ((int16_t*)filter)[(phase_count-ph) * alloc + tap_count-1-i] = ((int16_t*)filter)[ph * alloc + i]; } else { for (i = 1; i <= tap_count; i++) ((int16_t*)filter)[(phase_count-ph) * alloc + tap_count-i] = av_clip_int16(lrintf(tab[i] * scale / (norm - tab[0] + tab[tap_count]))); } break; case AV_SAMPLE_FMT_S32P: for(i=0;i<tap_count;i++) ((int32_t*)filter)[ph * alloc + i] = av_clipl_int32(llrint(tab[i] * scale / norm)); if (tap_count % 2 == 0) { for (i = 0; i < tap_count; i++) ((int32_t*)filter)[(phase_count-ph) * alloc + tap_count-1-i] = ((int32_t*)filter)[ph * alloc + i]; } else { for (i = 1; i <= tap_count; i++) ((int32_t*)filter)[(phase_count-ph) * alloc + tap_count-i] = av_clipl_int32(llrint(tab[i] * scale / (norm - tab[0] + tab[tap_count]))); } break; case AV_SAMPLE_FMT_FLTP: for(i=0;i<tap_count;i++) ((float*)filter)[ph * alloc + i] = tab[i] * scale / norm; if (tap_count % 2 == 0) { for (i = 0; i < tap_count; i++) ((float*)filter)[(phase_count-ph) * alloc + tap_count-1-i] = ((float*)filter)[ph * alloc + i]; } else { for (i = 1; i <= tap_count; i++) ((float*)filter)[(phase_count-ph) * alloc + tap_count-i] = tab[i] * scale / (norm - tab[0] + tab[tap_count]); } break; case AV_SAMPLE_FMT_DBLP: for(i=0;i<tap_count;i++) ((double*)filter)[ph * alloc + i] = tab[i] * scale / norm; if (tap_count % 2 == 0) { for (i = 0; i < tap_count; i++) ((double*)filter)[(phase_count-ph) * alloc + tap_count-1-i] = ((double*)filter)[ph * alloc + i]; } else { for (i = 1; i <= tap_count; i++) ((double*)filter)[(phase_count-ph) * alloc + tap_count-i] = tab[i] * scale / (norm - tab[0] + tab[tap_count]); } break; } } #if 0 { #define LEN 1024 int j,k; double sine[LEN + tap_count]; double filtered[LEN]; double maxff=-2, minff=2, maxsf=-2, minsf=2; for(i=0; i<LEN; i++){ double ss=0, sf=0, ff=0; for(j=0; j<LEN+tap_count; j++) sine[j]= cos(i*j*M_PI/LEN); for(j=0; j<LEN; j++){ double sum=0; ph=0; for(k=0; k<tap_count; k++) sum += filter[ph * tap_count + k] * sine[k+j]; filtered[j]= sum / (1<<FILTER_SHIFT); ss+= sine[j + center] * sine[j + center]; ff+= filtered[j] * filtered[j]; sf+= sine[j + center] * filtered[j]; } ss= sqrt(2*ss/LEN); ff= sqrt(2*ff/LEN); sf= 2*sf/LEN; maxff= FFMAX(maxff, ff); minff= FFMIN(minff, ff); maxsf= FFMAX(maxsf, sf); minsf= FFMIN(minsf, sf); if(i%11==0){ av_log(NULL, AV_LOG_ERROR, "i:%4d ss:%f ff:%13.6e-%13.6e sf:%13.6e-%13.6e\n", i, ss, maxff, minff, maxsf, minsf); minff=minsf= 2; maxff=maxsf= -2; } } } #endif fail: av_free(tab); av_free(sin_lut); return 0; }