Add const to (mostly) char* and make some functions static, which aren't used
[libav.git] / 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., 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 static 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 }