quicktime/ffmpeg/libavcodec/resample2.c

   1 /*
   2  * audio resampling
   3  * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  */
  20
  21 /**
  22  * @file resample2.c
  23  * audio resampling
  24  * @author Michael Niedermayer <michaelni@gmx.at>
  25  */
  26
  27 #include "avcodec.h"
  28 #include "common.h"
  29 #include "dsputil.h"
  30
  31 #if 1
  32 #define FILTER_SHIFT 15
  33
  34 #define FELEM int16_t
  35 #define FELEM2 int32_t
  36 #define FELEM_MAX INT16_MAX
  37 #define FELEM_MIN INT16_MIN
  38 #else
  39 #define FILTER_SHIFT 22
  40
  41 #define FELEM int32_t
  42 #define FELEM2 int64_t
  43 #define FELEM_MAX INT32_MAX
  44 #define FELEM_MIN INT32_MIN
  45 #endif
  46
  47
  48 typedef struct AVResampleContext{
  49     FELEM *filter_bank;
  50     int filter_length;
  51     int ideal_dst_incr;
  52     int dst_incr;
  53     int index;
  54     int frac;
  55     int src_incr;
  56     int compensation_distance;
  57     int phase_shift;
  58     int phase_mask;
  59     int linear;
  60 }AVResampleContext;
  61
  62 /**
  63  * 0th order modified bessel function of the first kind.
  64  */
  65 double bessel(double x){
  66     double v=1;
  67     double t=1;
  68     int i;
  69
  70     for(i=1; i<50; i++){
  71         t *= i;
  72         v += pow(x*x/4, i)/(t*t);
  73     }
  74     return v;
  75 }
  76
  77 /**
  78  * builds a polyphase filterbank.
  79  * @param factor resampling factor
  80  * @param scale wanted sum of coefficients for each filter
  81  * @param type 0->cubic, 1->blackman nuttall windowed sinc, 2->kaiser windowed sinc beta=16
  82  */
  83 void av_build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){
  84     int ph, i, v;
  85     double x, y, w, tab[tap_count];
  86     const int center= (tap_count-1)/2;
  87
  88     /* if upsampling, only need to interpolate, no filter */
  89     if (factor > 1.0)
  90         factor = 1.0;
  91
  92     for(ph=0;ph<phase_count;ph++) {
  93         double norm = 0;
  94         double e= 0;
  95         for(i=0;i<tap_count;i++) {
  96             x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor;
  97             if (x == 0) y = 1.0;
  98             else        y = sin(x) / x;
  99             switch(type){
 100             case 0:{
 101                 const float d= -0.5; //first order derivative = -0.5
 102                 x = fabs(((double)(i - center) - (double)ph / phase_count) * factor);
 103                 if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*(            -x*x + x*x*x);
 104                 else      y=                       d*(-4 + 8*x - 5*x*x + x*x*x);
 105                 break;}
 106             case 1:
 107                 w = 2.0*x / (factor*tap_count) + M_PI;
 108                 y *= 0.3635819 - 0.4891775 * cos(w) + 0.1365995 * cos(2*w) - 0.0106411 * cos(3*w);
 109                 break;
 110             case 2:
 111                 w = 2.0*x / (factor*tap_count*M_PI);
 112                 y *= bessel(16*sqrt(FFMAX(1-w*w, 0)));
 113                 break;
 114             }
 115
 116             tab[i] = y;
 117             norm += y;
 118         }
 119
 120         /* normalize so that an uniform color remains the same */
 121         for(i=0;i<tap_count;i++) {
 122             v = clip(lrintf(tab[i] * scale / norm + e), FELEM_MIN, FELEM_MAX);
 123             filter[ph * tap_count + i] = v;
 124             e += tab[i] * scale / norm - v;
 125         }
 126     }
 127 }
 128
 129 /**
 130  * initalizes a audio resampler.
 131  * note, if either rate is not a integer then simply scale both rates up so they are
 132  */
 133 AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){
 134     AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
 135     double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
 136     int phase_count= 1<<phase_shift;
 137
 138     c->phase_shift= phase_shift;
 139     c->phase_mask= phase_count-1;
 140     c->linear= linear;
 141
 142     c->filter_length= FFMAX(ceil(filter_size/factor), 1);
 143     c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
 144     av_build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, 1);
 145     memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
 146     c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];
 147
 148     c->src_incr= out_rate;
 149     c->ideal_dst_incr= c->dst_incr= in_rate * phase_count;
 150     c->index= -phase_count*((c->filter_length-1)/2);
 151
 152     return c;
 153 }
 154
 155 void av_resample_close(AVResampleContext *c){
 156     av_freep(&c->filter_bank);
 157     av_freep(&c);
 158 }
 159
 160 /**
 161  * Compensates samplerate/timestamp drift. The compensation is done by changing
 162  * the resampler parameters, so no audible clicks or similar distortions ocur
 163  * @param compensation_distance distance in output samples over which the compensation should be performed
 164  * @param sample_delta number of output samples which should be output less
 165  *
 166  * example: av_resample_compensate(c, 10, 500)
 167  * here instead of 510 samples only 500 samples would be output
 168  *
 169  * note, due to rounding the actual compensation might be slightly different,
 170  * especially if the compensation_distance is large and the in_rate used during init is small
 171  */
 172 void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){
 173 //    sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
 174     c->compensation_distance= compensation_distance;
 175     c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
 176 }
 177
 178 /**
 179  * resamples.
 180  * @param src an array of unconsumed samples
 181  * @param consumed the number of samples of src which have been consumed are returned here
 182  * @param src_size the number of unconsumed samples available
 183  * @param dst_size the amount of space in samples available in dst
 184  * @param update_ctx if this is 0 then the context wont be modified, that way several channels can be resampled with the same context
 185  * @return the number of samples written in dst or -1 if an error occured
 186  */
 187 int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){
 188     int dst_index, i;
 189     int index= c->index;
 190     int frac= c->frac;
 191     int dst_incr_frac= c->dst_incr % c->src_incr;
 192     int dst_incr=      c->dst_incr / c->src_incr;
 193     int compensation_distance= c->compensation_distance;
 194
 195   if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){
 196         int64_t index2= ((int64_t)index)<<32;
 197         int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr;
 198         dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);
 199
 200         for(dst_index=0; dst_index < dst_size; dst_index++){
 201             dst[dst_index] = src[index2>>32];
 202             index2 += incr;
 203         }
 204         frac += dst_index * dst_incr_frac;
 205         index += dst_index * dst_incr;
 206         index += frac / c->src_incr;
 207         frac %= c->src_incr;
 208   }else{
 209     for(dst_index=0; dst_index < dst_size; dst_index++){
 210         FELEM *filter= c->filter_bank + c->filter_length*(index & c->phase_mask);
 211         int sample_index= index >> c->phase_shift;
 212         FELEM2 val=0;
 213
 214         if(sample_index < 0){
 215             for(i=0; i<c->filter_length; i++)
 216                 val += src[ABS(sample_index + i) % src_size] * filter[i];
 217         }else if(sample_index + c->filter_length > src_size){
 218             break;
 219         }else if(c->linear){
 220             int64_t v=0;
 221             int sub_phase= (frac<<8) / c->src_incr;
 222             for(i=0; i<c->filter_length; i++){
 223                 int64_t coeff= filter[i]*(256 - sub_phase) + filter[i + c->filter_length]*sub_phase;
 224                 v += src[sample_index + i] * coeff;
 225             }
 226             val= v>>8;
 227         }else{
 228             for(i=0; i<c->filter_length; i++){
 229                 val += src[sample_index + i] * (FELEM2)filter[i];
 230             }
 231         }
 232
 233         val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT;
 234         dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val;
 235
 236         frac += dst_incr_frac;
 237         index += dst_incr;
 238         if(frac >= c->src_incr){
 239             frac -= c->src_incr;
 240             index++;
 241         }
 242
 243         if(dst_index + 1 == compensation_distance){
 244             compensation_distance= 0;
 245             dst_incr_frac= c->ideal_dst_incr % c->src_incr;
 246             dst_incr=      c->ideal_dst_incr / c->src_incr;
 247         }
 248     }
 249   }
 250     *consumed= FFMAX(index, 0) >> c->phase_shift;
 251     if(index>=0) index &= c->phase_mask;
 252
 253     if(compensation_distance){
 254         compensation_distance -= dst_index;
 255         assert(compensation_distance > 0);
 256     }
 257     if(update_ctx){
 258         c->frac= frac;
 259         c->index= index;
 260         c->dst_incr= dst_incr_frac + c->src_incr*dst_incr;
 261         c->compensation_distance= compensation_distance;
 262     }
 263 #if 0
 264     if(update_ctx && !c->compensation_distance){
 265 #undef rand
 266         av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
 267 av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
 268     }
 269 #endif
 270
 271     return dst_index;
 272 }