Statistics
| Branch: | Revision:

ffmpeg / libavcodec / resample2.c @ 5509bffa

History | View | Annotate | Download (9.24 KB)

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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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((int)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
}