1/*
2 * audio resampling
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file libavcodec/resample2.c
24 * audio resampling
25 * @author Michael Niedermayer <michaelni@gmx.at>
26 */
27
28#include "avcodec.h"
29#include "dsputil.h"
30
31#ifndef CONFIG_RESAMPLE_HP
32#define FILTER_SHIFT 15
33
34#define FELEM int16_t
35#define FELEM2 int32_t
36#define FELEML int64_t
37#define FELEM_MAX INT16_MAX
38#define FELEM_MIN INT16_MIN
39#define WINDOW_TYPE 9
40#elif !defined(CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE)
41#define FILTER_SHIFT 30
42
43#define FELEM int32_t
44#define FELEM2 int64_t
45#define FELEML int64_t
46#define FELEM_MAX INT32_MAX
47#define FELEM_MIN INT32_MIN
48#define WINDOW_TYPE 12
49#else
50#define FILTER_SHIFT 0
51
52#define FELEM double
53#define FELEM2 double
54#define FELEML double
55#define WINDOW_TYPE 24
56#endif
57
58
59typedef struct AVResampleContext{
60    FELEM *filter_bank;
61    int filter_length;
62    int ideal_dst_incr;
63    int dst_incr;
64    int index;
65    int frac;
66    int src_incr;
67    int compensation_distance;
68    int phase_shift;
69    int phase_mask;
70    int linear;
71}AVResampleContext;
72
73/**
74 * 0th order modified bessel function of the first kind.
75 */
76static double bessel(double x){
77    double v=1;
78    double t=1;
79    int i;
80
81    x= x*x/4;
82    for(i=1; i<50; i++){
83        t *= x/(i*i);
84        v += t;
85    }
86    return v;
87}
88
89/**
90 * builds a polyphase filterbank.
91 * @param factor resampling factor
92 * @param scale wanted sum of coefficients for each filter
93 * @param type 0->cubic, 1->blackman nuttall windowed sinc, 2..16->kaiser windowed sinc beta=2..16
94 */
95void av_build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){
96    int ph, i;
97    double x, y, w, tab[tap_count];
98    const int center= (tap_count-1)/2;
99
100    /* if upsampling, only need to interpolate, no filter */
101    if (factor > 1.0)
102        factor = 1.0;
103
104    for(ph=0;ph<phase_count;ph++) {
105        double norm = 0;
106        for(i=0;i<tap_count;i++) {
107            x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor;
108            if (x == 0) y = 1.0;
109            else        y = sin(x) / x;
110            switch(type){
111            case 0:{
112                const float d= -0.5; //first order derivative = -0.5
113                x = fabs(((double)(i - center) - (double)ph / phase_count) * factor);
114                if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*(            -x*x + x*x*x);
115                else      y=                       d*(-4 + 8*x - 5*x*x + x*x*x);
116                break;}
117            case 1:
118                w = 2.0*x / (factor*tap_count) + M_PI;
119                y *= 0.3635819 - 0.4891775 * cos(w) + 0.1365995 * cos(2*w) - 0.0106411 * cos(3*w);
120                break;
121            default:
122                w = 2.0*x / (factor*tap_count*M_PI);
123                y *= bessel(type*sqrt(FFMAX(1-w*w, 0)));
124                break;
125            }
126
127            tab[i] = y;
128            norm += y;
129        }
130
131        /* normalize so that an uniform color remains the same */
132        for(i=0;i<tap_count;i++) {
133#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
134            filter[ph * tap_count + i] = tab[i] / norm;
135#else
136            filter[ph * tap_count + i] = av_clip(lrintf(tab[i] * scale / norm), FELEM_MIN, FELEM_MAX);
137#endif
138        }
139    }
140#if 0
141    {
142#define LEN 1024
143        int j,k;
144        double sine[LEN + tap_count];
145        double filtered[LEN];
146        double maxff=-2, minff=2, maxsf=-2, minsf=2;
147        for(i=0; i<LEN; i++){
148            double ss=0, sf=0, ff=0;
149            for(j=0; j<LEN+tap_count; j++)
150                sine[j]= cos(i*j*M_PI/LEN);
151            for(j=0; j<LEN; j++){
152                double sum=0;
153                ph=0;
154                for(k=0; k<tap_count; k++)
155                    sum += filter[ph * tap_count + k] * sine[k+j];
156                filtered[j]= sum / (1<<FILTER_SHIFT);
157                ss+= sine[j + center] * sine[j + center];
158                ff+= filtered[j] * filtered[j];
159                sf+= sine[j + center] * filtered[j];
160            }
161            ss= sqrt(2*ss/LEN);
162            ff= sqrt(2*ff/LEN);
163            sf= 2*sf/LEN;
164            maxff= FFMAX(maxff, ff);
165            minff= FFMIN(minff, ff);
166            maxsf= FFMAX(maxsf, sf);
167            minsf= FFMIN(minsf, sf);
168            if(i%11==0){
169                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);
170                minff=minsf= 2;
171                maxff=maxsf= -2;
172            }
173        }
174    }
175#endif
176}
177
178AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){
179    AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
180    double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
181    int phase_count= 1<<phase_shift;
182
183    c->phase_shift= phase_shift;
184    c->phase_mask= phase_count-1;
185    c->linear= linear;
186
187    c->filter_length= FFMAX((int)ceil(filter_size/factor), 1);
188    c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
189    av_build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, WINDOW_TYPE);
190    memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
191    c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];
192
193    c->src_incr= out_rate;
194    c->ideal_dst_incr= c->dst_incr= in_rate * phase_count;
195    c->index= -phase_count*((c->filter_length-1)/2);
196
197    return c;
198}
199
200void av_resample_close(AVResampleContext *c){
201    av_freep(&c->filter_bank);
202    av_freep(&c);
203}
204
205void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){
206//    sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
207    c->compensation_distance= compensation_distance;
208    c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
209}
210
211int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){
212    int dst_index, i;
213    int index= c->index;
214    int frac= c->frac;
215    int dst_incr_frac= c->dst_incr % c->src_incr;
216    int dst_incr=      c->dst_incr / c->src_incr;
217    int compensation_distance= c->compensation_distance;
218
219  if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){
220        int64_t index2= ((int64_t)index)<<32;
221        int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr;
222        dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);
223
224        for(dst_index=0; dst_index < dst_size; dst_index++){
225            dst[dst_index] = src[index2>>32];
226            index2 += incr;
227        }
228        frac += dst_index * dst_incr_frac;
229        index += dst_index * dst_incr;
230        index += frac / c->src_incr;
231        frac %= c->src_incr;
232  }else{
233    for(dst_index=0; dst_index < dst_size; dst_index++){
234        FELEM *filter= c->filter_bank + c->filter_length*(index & c->phase_mask);
235        int sample_index= index >> c->phase_shift;
236        FELEM2 val=0;
237
238        if(sample_index < 0){
239            for(i=0; i<c->filter_length; i++)
240                val += src[FFABS(sample_index + i) % src_size] * filter[i];
241        }else if(sample_index + c->filter_length > src_size){
242            break;
243        }else if(c->linear){
244            FELEM2 v2=0;
245            for(i=0; i<c->filter_length; i++){
246                val += src[sample_index + i] * (FELEM2)filter[i];
247                v2  += src[sample_index + i] * (FELEM2)filter[i + c->filter_length];
248            }
249            val+=(v2-val)*(FELEML)frac / c->src_incr;
250        }else{
251            for(i=0; i<c->filter_length; i++){
252                val += src[sample_index + i] * (FELEM2)filter[i];
253            }
254        }
255
256#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
257        dst[dst_index] = av_clip_int16(lrintf(val));
258#else
259        val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT;
260        dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val;
261#endif
262
263        frac += dst_incr_frac;
264        index += dst_incr;
265        if(frac >= c->src_incr){
266            frac -= c->src_incr;
267            index++;
268        }
269
270        if(dst_index + 1 == compensation_distance){
271            compensation_distance= 0;
272            dst_incr_frac= c->ideal_dst_incr % c->src_incr;
273            dst_incr=      c->ideal_dst_incr / c->src_incr;
274        }
275    }
276  }
277    *consumed= FFMAX(index, 0) >> c->phase_shift;
278    if(index>=0) index &= c->phase_mask;
279
280    if(compensation_distance){
281        compensation_distance -= dst_index;
282        assert(compensation_distance > 0);
283    }
284    if(update_ctx){
285        c->frac= frac;
286        c->index= index;
287        c->dst_incr= dst_incr_frac + c->src_incr*dst_incr;
288        c->compensation_distance= compensation_distance;
289    }
290#if 0
291    if(update_ctx && !c->compensation_distance){
292#undef rand
293        av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
294av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
295    }
296#endif
297
298    return dst_index;
299}
300