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MicroDexed/sin.h

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1.7 KiB

/*
* Copyright 2012 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
class Sin {
public:
Sin();
static void init();
static int32_t lookup(int32_t phase);
static int32_t compute(int32_t phase);
// A more accurate sine, both input and output Q30
static int32_t compute10(int32_t phase);
};
#define SIN_LG_N_SAMPLES 10
#define SIN_N_SAMPLES (1 << SIN_LG_N_SAMPLES)
#define SIN_INLINE
// Use twice as much RAM for the LUT but avoid a little computation
#define SIN_DELTA
#ifdef SIN_DELTA
extern int32_t sintab[SIN_N_SAMPLES << 1];
#else
extern int32_t sintab[SIN_N_SAMPLES + 1];
#endif
#ifdef SIN_INLINE
inline
int32_t Sin::lookup(int32_t phase) {
const int SHIFT = 24 - SIN_LG_N_SAMPLES;
int lowbits = phase & ((1 << SHIFT) - 1);
#ifdef SIN_DELTA
int phase_int = (phase >> (SHIFT - 1)) & ((SIN_N_SAMPLES - 1) << 1);
int dy = sintab[phase_int];
int y0 = sintab[phase_int + 1];
return y0 + (((int64_t)dy * (int64_t)lowbits) >> SHIFT);
#else
int phase_int = (phase >> SHIFT) & (SIN_N_SAMPLES - 1);
int y0 = sintab[phase_int];
int y1 = sintab[phase_int + 1];
return y0 + (((int64_t)(y1 - y0) * (int64_t)lowbits) >> SHIFT);
#endif
}
#endif