/* * Copyright 2022 The Android Open Source Project * * 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. */ package org.hyphonate.megaaudio.player.sources; /** * An AudioSourceProvider for multi-channel sine waves with control over which * channels have audio data and which channels have silence. */ public class SparseChannelAudioSource extends WaveTableSource { /** * The number of SAMPLES in the Sin Wave table. * This is plenty of samples for a clear sine wave. * the + 1 is to avoid special handling of the interpolation on the last sample. */ static final int WAVETABLE_LENGTH = 2049; int mChannelsMask; public SparseChannelAudioSource(int mask) { super(); float[] waveTbl = new float[WAVETABLE_LENGTH]; WaveTableSource.genSinWave(waveTbl); setWaveTable(waveTbl); mChannelsMask = mask; } public void setMask(int mask) { mChannelsMask = mask; } private int channelNumToMask(int chanNum) { if (chanNum <= 0) { return 0; } return 1 << (chanNum - 1); } @Override public int pull(float[] buffer, int numFrames, int numChans) { final float phaseIncr = mFreq * mFNInverse; int outIndex = 0; for (int frameIndex = 0; frameIndex < numFrames; frameIndex++) { // 'mod' back into the waveTable while (mSrcPhase >= (float) mNumWaveTblSamples) { mSrcPhase -= (float) mNumWaveTblSamples; } // linear-interpolate int srcIndex = (int) mSrcPhase; float delta0 = mSrcPhase - (float) srcIndex; float delta1 = 1.0f - delta0; float value = ((mWaveTbl[srcIndex] * delta0) + (mWaveTbl[srcIndex + 1] * delta1)); // Put the same value in all channels. // This is inefficient and should be pulled out of this loop for (int chanIndex = 0; chanIndex < numChans; chanIndex++) { if ((mChannelsMask & (1 << chanIndex)) != 0) { buffer[outIndex++] = value; } else { buffer[outIndex++] = 0.0f; } } mSrcPhase += phaseIncr; } return numFrames; } }