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, see <http://www.gnu.org/licenses/>.
19 */
20
21/**
22 * @file libavcodec/resample2.c
23 * audio resampling
24 * @author Michael Niedermayer <michaelni@gmx.at>
25 */
26
27#include "avcodec.h"
28#include "dsputil.h"
29
30#ifndef CONFIG_RESAMPLE_HP
31#define FILTER_SHIFT 15
32
33#define FELEM int16_t
34#define FELEM2 int32_t
35#define FELEML int64_t
36#define FELEM_MAX INT16_MAX
37#define FELEM_MIN INT16_MIN
38#define WINDOW_TYPE 9
39#elif !defined(CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE)
40#define FILTER_SHIFT 30
41
42#define FELEM int32_t
43#define FELEM2 int64_t
44#define FELEML int64_t
45#define FELEM_MAX INT32_MAX
46#define FELEM_MIN INT32_MIN
47#define WINDOW_TYPE 12
48#else
49#define FILTER_SHIFT 0
50
51#define FELEM double
52#define FELEM2 double
53#define FELEML double
54#define WINDOW_TYPE 24
55#endif
56
57
58typedef struct AVResampleContext{
59    FELEM *filter_bank;
60    int filter_length;
61    int ideal_dst_incr;
62    int dst_incr;
63    int index;
64    int frac;
65    int src_incr;
66    int compensation_distance;
67    int phase_shift;
68    int phase_mask;
69    int linear;
70}AVResampleContext;
71
72/**
73 * 0th order modified bessel function of the first kind.
74 */
75static double bessel(double x){
76    double v=1;
77    double t=1;
78    int i;
79
80    x= x*x/4;
81    for(i=1; i<50; i++){
82        t *= x/(i*i);
83        v += t;
84    }
85    return v;
86}
87
88/**
89 * builds a polyphase filterbank.
90 * @param factor resampling factor
91 * @param scale wanted sum of coefficients for each filter
92 * @param type 0->cubic, 1->blackman nuttall windowed sinc, 2..16->kaiser windowed sinc beta=2..16
93 */
94void av_build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){
95    int ph, i;
96    double x, y, w, tab[tap_count];
97    const int center= (tap_count-1)/2;
98
99    /* if upsampling, only need to interpolate, no filter */
100    if (factor > 1.0)
101        factor = 1.0;
102
103    for(ph=0;ph<phase_count;ph++) {
104        double norm = 0;
105        for(i=0;i<tap_count;i++) {
106            x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor;
107            if (x == 0) y = 1.0;
108            else        y = sin(x) / x;
109            switch(type){
110            case 0:{
111                const float d= -0.5; //first order derivative = -0.5
112                x = fabs(((double)(i - center) - (double)ph / phase_count) * factor);
113                if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*(            -x*x + x*x*x);
114                else      y=                       d*(-4 + 8*x - 5*x*x + x*x*x);
115                break;}
116            case 1:
117                w = 2.0*x / (factor*tap_count) + M_PI;
118                y *= 0.3635819 - 0.4891775 * cos(w) + 0.1365995 * cos(2*w) - 0.0106411 * cos(3*w);
119                break;
120            default:
121                w = 2.0*x / (factor*tap_count*M_PI);
122                y *= bessel(type*sqrt(FFMAX(1-w*w, 0)));
123                break;
124            }
125
126            tab[i] = y;
127            norm += y;
128        }
129
130        /* normalize so that an uniform color remains the same */
131        for(i=0;i<tap_count;i++) {
132#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
133            filter[ph * tap_count + i] = tab[i] / norm;
134#else
135            filter[ph * tap_count + i] = av_clip(lrintf(tab[i] * scale / norm), FELEM_MIN, FELEM_MAX);
136#endif
137        }
138    }
139#if 0
140    {
141#define LEN 1024
142        int j,k;
143        double sine[LEN + tap_count];
144        double filtered[LEN];
145        double maxff=-2, minff=2, maxsf=-2, minsf=2;
146        for(i=0; i<LEN; i++){
147            double ss=0, sf=0, ff=0;
148            for(j=0; j<LEN+tap_count; j++)
149                sine[j]= cos(i*j*M_PI/LEN);
150            for(j=0; j<LEN; j++){
151                double sum=0;
152                ph=0;
153                for(k=0; k<tap_count; k++)
154                    sum += filter[ph * tap_count + k] * sine[k+j];
155                filtered[j]= sum / (1<<FILTER_SHIFT);
156                ss+= sine[j + center] * sine[j + center];
157                ff+= filtered[j] * filtered[j];
158                sf+= sine[j + center] * filtered[j];
159            }
160            ss= sqrt(2*ss/LEN);
161            ff= sqrt(2*ff/LEN);
162            sf= 2*sf/LEN;
163            maxff= FFMAX(maxff, ff);
164            minff= FFMIN(minff, ff);
165            maxsf= FFMAX(maxsf, sf);
166            minsf= FFMIN(minsf, sf);
167            if(i%11==0){
168                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);
169                minff=minsf= 2;
170                maxff=maxsf= -2;
171            }
172        }
173    }
174#endif
175}
176
177AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){
178    AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
179    double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
180    int phase_count= 1<<phase_shift;
181
182    c->phase_shift= phase_shift;
183    c->phase_mask= phase_count-1;
184    c->linear= linear;
185
186    c->filter_length= FFMAX((int)ceil(filter_size/factor), 1);
187    c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
188    av_build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, WINDOW_TYPE);
189    memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
190    c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];
191
192    c->src_incr= out_rate;
193    c->ideal_dst_incr= c->dst_incr= in_rate * phase_count;
194    c->index= -phase_count*((c->filter_length-1)/2);
195
196    return c;
197}
198
199void av_resample_close(AVResampleContext *c){
200    av_freep(&c->filter_bank);
201    av_freep(&c);
202}
203
204void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){
205//    sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
206    c->compensation_distance= compensation_distance;
207    c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
208}
209
210int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){
211    int dst_index, i;
212    int index= c->index;
213    int frac= c->frac;
214    int dst_incr_frac= c->dst_incr % c->src_incr;
215    int dst_incr=      c->dst_incr / c->src_incr;
216    int compensation_distance= c->compensation_distance;
217
218  if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){
219        int64_t index2= ((int64_t)index)<<32;
220        int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr;
221        dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);
222
223        for(dst_index=0; dst_index < dst_size; dst_index++){
224            dst[dst_index] = src[index2>>32];
225            index2 += incr;
226        }
227        frac += dst_index * dst_incr_frac;
228        index += dst_index * dst_incr;
229        index += frac / c->src_incr;
230        frac %= c->src_incr;
231  }else{
232    for(dst_index=0; dst_index < dst_size; dst_index++){
233        FELEM *filter= c->filter_bank + c->filter_length*(index & c->phase_mask);
234        int sample_index= index >> c->phase_shift;
235        FELEM2 val=0;
236
237        if(sample_index < 0){
238            for(i=0; i<c->filter_length; i++)
239                val += src[FFABS(sample_index + i) % src_size] * filter[i];
240        }else if(sample_index + c->filter_length > src_size){
241            break;
242        }else if(c->linear){
243            FELEM2 v2=0;
244            for(i=0; i<c->filter_length; i++){
245                val += src[sample_index + i] * (FELEM2)filter[i];
246                v2  += src[sample_index + i] * (FELEM2)filter[i + c->filter_length];
247            }
248            val+=(v2-val)*(FELEML)frac / c->src_incr;
249        }else{
250            for(i=0; i<c->filter_length; i++){
251                val += src[sample_index + i] * (FELEM2)filter[i];
252            }
253        }
254
255#ifdef CONFIG_RESAMPLE_AUDIOPHILE_KIDDY_MODE
256        dst[dst_index] = av_clip_int16(lrintf(val));
257#else
258        val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT;
259        dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val;
260#endif
261
262        frac += dst_incr_frac;
263        index += dst_incr;
264        if(frac >= c->src_incr){
265            frac -= c->src_incr;
266            index++;
267        }
268
269        if(dst_index + 1 == compensation_distance){
270            compensation_distance= 0;
271            dst_incr_frac= c->ideal_dst_incr % c->src_incr;
272            dst_incr=      c->ideal_dst_incr / c->src_incr;
273        }
274    }
275  }
276    *consumed= FFMAX(index, 0) >> c->phase_shift;
277    if(index>=0) index &= c->phase_mask;
278
279    if(compensation_distance){
280        compensation_distance -= dst_index;
281        assert(compensation_distance > 0);
282    }
283    if(update_ctx){
284        c->frac= frac;
285        c->index= index;
286        c->dst_incr= dst_incr_frac + c->src_incr*dst_incr;
287        c->compensation_distance= compensation_distance;
288    }
289#if 0
290    if(update_ctx && !c->compensation_distance){
291#undef rand
292        av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
293av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
294    }
295#endif
296
297    return dst_index;
298}
299