1 /* 2 * Copyright 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <math.h> 18 #include <unistd.h> 19 20 #include "TriangleOscillator.h" 21 TriangleOscillator()22TriangleOscillator::TriangleOscillator() 23 : OscillatorBase() { 24 } 25 onProcess(int32_t numFrames)26int32_t TriangleOscillator::onProcess(int32_t numFrames) { 27 const float *frequencies = frequency.getBuffer(); 28 const float *amplitudes = amplitude.getBuffer(); 29 float *buffer = output.getBuffer(); 30 31 // Use the phase directly as a non-band-limited "triangle". 32 // WARNING: This will generate unpleasant aliasing artifacts at higher frequencies. 33 for (int i = 0; i < numFrames; i++) { 34 float phase = incrementPhase(frequencies[i]); // phase ranges from -1 to +1 35 float triangle = 2.0f * ((phase < 0.0f) ? (0.5f + phase): (0.5f - phase)); 36 *buffer++ = triangle * amplitudes[i]; 37 } 38 39 return numFrames; 40 } 41