56 lines
2.0 KiB
C
56 lines
2.0 KiB
C
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/* Copyright (c) 2018 lvqcl. All rights reserved.
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*
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* This library is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at
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* your option) any later version.
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*
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* This library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
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* General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef UTIL_H_
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#define UTIL_H_
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#ifndef min
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#define min(a,b) (((a)<(b))?(a):(b))
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#endif
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#ifndef max
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#define max(a,b) (((a)>(b))?(a):(b))
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#endif
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static inline unsigned local_gcd(unsigned a, unsigned b)
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{
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if (a == 0 || b == 0) return 0;
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unsigned c = a % b;
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while (c != 0) { a = b; b = c; c = a % b; }
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return b;
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}
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/*
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In: *r1 and *r2: samplerates;
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Out: *r1 and *r2: numbers of samples;
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multiply r1 and r2 by n so that durations is 1/N th of second;
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limit n so that r1 and r2 aren't bigger than M
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*/
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static void samples_len(unsigned* r1, unsigned* r2, unsigned N, unsigned M) // example: r1 = 44100, r2 = 48000, N = 20, M = 8192
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{
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if (r1 == 0 || r2 == 0) return;
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unsigned v = local_gcd(*r1, *r2); // v = 300
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*r1 /= v; *r2 /= v; // r1 = 147; r2 = 160 == 1/300th of second
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unsigned n = (v + N-1) / N; // n = 300/20 = 15 times
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unsigned z = max(*r1, *r2); // z = 160
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if (z*n > M) n = M / z; // 160*15 = 2400 < 8192;; if M == 1024: n = 1024/160 = 6; 160*6 = 960
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if (n < 1) n = 1;
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*r1 *= n; *r2 *= n; // r1 = 147*15 = 2205 samples, r2 = 160*15 = 2400 samples
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}
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#endif
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