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
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    const AVClass *av_class;
61    FELEM *filter_bank;
62    int filter_length;
63    int ideal_dst_incr;
64    int dst_incr;
65    int index;
66    int frac;
67    int src_incr;
68    int compensation_distance;
69    int phase_shift;
70    int phase_mask;
71    int linear;
72}AVResampleContext;
73
74/**
75 * 0th order modified bessel function of the first kind.
76 */
77static double bessel(double x){
78    double v=1;
79    double lastv=0;
80    double t=1;
81    int i;
82
83    x= x*x/4;
84    for(i=1; v != lastv; i++){
85        lastv=v;
86        t *= x/(i*i);
87        v += t;
88    }
89    return v;
90}
91
92/**
93 * builds a polyphase filterbank.
94 * @param factor resampling factor
95 * @param scale wanted sum of coefficients for each filter
96 * @param type 0->cubic, 1->blackman nuttall windowed sinc, 2..16->kaiser windowed sinc beta=2..16
97 */
98static void build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){
99    int ph, i;
100    double x, y, w, tab[tap_count];
101    const int center= (tap_count-1)/2;
102
103    /* if upsampling, only need to interpolate, no filter */
104    if (factor > 1.0)
105        factor = 1.0;
106
107    for(ph=0;ph<phase_count;ph++) {
108        double norm = 0;
109        for(i=0;i<tap_count;i++) {
110            x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor;
111            if (x == 0) y = 1.0;
112            else        y = sin(x) / x;
113            switch(type){
114            case 0:{
115                const float d= -0.5; //first order derivative = -0.5
116                x = fabs(((double)(i - center) - (double)ph / phase_count) * factor);
117                if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*(            -x*x + x*x*x);
118                else      y=                       d*(-4 + 8*x - 5*x*x + x*x*x);
119                break;}
120            case 1:
121                w = 2.0*x / (factor*tap_count) + M_PI;
122                y *= 0.3635819 - 0.4891775 * cos(w) + 0.1365995 * cos(2*w) - 0.0106411 * cos(3*w);
123                break;
124            default:
125                w = 2.0*x / (factor*tap_count*M_PI);
126                y *= bessel(type*sqrt(FFMAX(1-w*w, 0)));
127                break;
128            }
129
130            tab[i] = y;
131            norm += y;
132        }
133
134        /* normalize so that an uniform color remains the same */
135        for(i=0;i<tap_count;i++) {
136#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
137            filter[ph * tap_count + i] = tab[i] / norm;
138#else
139            filter[ph * tap_count + i] = av_clip(lrintf(tab[i] * scale / norm), FELEM_MIN, FELEM_MAX);
140#endif
141        }
142    }
143#if 0
144    {
145#define LEN 1024
146        int j,k;
147        double sine[LEN + tap_count];
148        double filtered[LEN];
149        double maxff=-2, minff=2, maxsf=-2, minsf=2;
150        for(i=0; i<LEN; i++){
151            double ss=0, sf=0, ff=0;
152            for(j=0; j<LEN+tap_count; j++)
153                sine[j]= cos(i*j*M_PI/LEN);
154            for(j=0; j<LEN; j++){
155                double sum=0;
156                ph=0;
157                for(k=0; k<tap_count; k++)
158                    sum += filter[ph * tap_count + k] * sine[k+j];
159                filtered[j]= sum / (1<<FILTER_SHIFT);
160                ss+= sine[j + center] * sine[j + center];
161                ff+= filtered[j] * filtered[j];
162                sf+= sine[j + center] * filtered[j];
163            }
164            ss= sqrt(2*ss/LEN);
165            ff= sqrt(2*ff/LEN);
166            sf= 2*sf/LEN;
167            maxff= FFMAX(maxff, ff);
168            minff= FFMIN(minff, ff);
169            maxsf= FFMAX(maxsf, sf);
170            minsf= FFMIN(minsf, sf);
171            if(i%11==0){
172                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);
173                minff=minsf= 2;
174                maxff=maxsf= -2;
175            }
176        }
177    }
178#endif
179}
180
181AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){
182    AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
183    double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
184    int phase_count= 1<<phase_shift;
185
186    c->phase_shift= phase_shift;
187    c->phase_mask= phase_count-1;
188    c->linear= linear;
189
190    c->filter_length= FFMAX((int)ceil(filter_size/factor), 1);
191    c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
192    build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, WINDOW_TYPE);
193    memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
194    c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];
195
196    c->src_incr= out_rate;
197    c->ideal_dst_incr= c->dst_incr= in_rate * phase_count;
198    c->index= -phase_count*((c->filter_length-1)/2);
199
200    return c;
201}
202
203void av_resample_close(AVResampleContext *c){
204    av_freep(&c->filter_bank);
205    av_freep(&c);
206}
207
208void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){
209//    sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
210    c->compensation_distance= compensation_distance;
211    c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
212}
213
214int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){
215    int dst_index, i;
216    int index= c->index;
217    int frac= c->frac;
218    int dst_incr_frac= c->dst_incr % c->src_incr;
219    int dst_incr=      c->dst_incr / c->src_incr;
220    int compensation_distance= c->compensation_distance;
221
222  if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){
223        int64_t index2= ((int64_t)index)<<32;
224        int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr;
225        dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);
226
227        for(dst_index=0; dst_index < dst_size; dst_index++){
228            dst[dst_index] = src[index2>>32];
229            index2 += incr;
230        }
231        frac += dst_index * dst_incr_frac;
232        index += dst_index * dst_incr;
233        index += frac / c->src_incr;
234        frac %= c->src_incr;
235  }else{
236    for(dst_index=0; dst_index < dst_size; dst_index++){
237        FELEM *filter= c->filter_bank + c->filter_length*(index & c->phase_mask);
238        int sample_index= index >> c->phase_shift;
239        FELEM2 val=0;
240
241        if(sample_index < 0){
242            for(i=0; i<c->filter_length; i++)
243                val += src[FFABS(sample_index + i) % src_size] * filter[i];
244        }else if(sample_index + c->filter_length > src_size){
245            break;
246        }else if(c->linear){
247            FELEM2 v2=0;
248            for(i=0; i<c->filter_length; i++){
249                val += src[sample_index + i] * (FELEM2)filter[i];
250                v2  += src[sample_index + i] * (FELEM2)filter[i + c->filter_length];
251            }
252            val+=(v2-val)*(FELEML)frac / c->src_incr;
253        }else{
254            for(i=0; i<c->filter_length; i++){
255                val += src[sample_index + i] * (FELEM2)filter[i];
256            }
257        }
258
259#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
260        dst[dst_index] = av_clip_int16(lrintf(val));
261#else
262        val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT;
263        dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val;
264#endif
265
266        frac += dst_incr_frac;
267        index += dst_incr;
268        if(frac >= c->src_incr){
269            frac -= c->src_incr;
270            index++;
271        }
272
273        if(dst_index + 1 == compensation_distance){
274            compensation_distance= 0;
275            dst_incr_frac= c->ideal_dst_incr % c->src_incr;
276            dst_incr=      c->ideal_dst_incr / c->src_incr;
277        }
278    }
279  }
280    *consumed= FFMAX(index, 0) >> c->phase_shift;
281    if(index>=0) index &= c->phase_mask;
282
283    if(compensation_distance){
284        compensation_distance -= dst_index;
285        assert(compensation_distance > 0);
286    }
287    if(update_ctx){
288        c->frac= frac;
289        c->index= index;
290        c->dst_incr= dst_incr_frac + c->src_incr*dst_incr;
291        c->compensation_distance= compensation_distance;
292    }
293#if 0
294    if(update_ctx && !c->compensation_distance){
295#undef rand
296        av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
297av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
298    }
299#endif
300
301    return dst_index;
302}
303