samples/iolib/src/main/cpp/player/OneShotSampleSource.cpp

/*
 * Copyright (C) 2019 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.
 */

#include <string.h>

#include "io/wav/WavStreamReader.h"

#include "OneShotSampleSource.h"

namespace iolib {

void OneShotSampleSource::mixAudio(float* outBuff, int numChannels, int32_t numFrames) {
    int32_t numSampleFrames = mSampleBuffer->getNumSampleFrames();
    int32_t numWriteFrames = mIsPlaying
                         ? std::min(numFrames, numSampleFrames - mCurFrameIndex)
                         : 0;

    if (numWriteFrames != 0) {
        // Mix in the samples
        // int32_t lastIndex = mCurFrameIndex + numWriteFrames;

        // investigate unrolling this loop...
        const float* data  = mSampleBuffer->getSampleData();
        if (numChannels == 1) {
            // MONO output
            for (int32_t frameIndex = 0; frameIndex < numWriteFrames; frameIndex++) {
                outBuff[frameIndex] += data[mCurFrameIndex++];
            }
        } else if (numChannels == 2) {
            // STEREO output
            int dstSampleIndex = 0;
            float leftGain = -(-mPan + 1.0) / 2.0f;
            float rightGain = (mPan + 1.0) / 2.0f;
            for (int32_t frameIndex = 0; frameIndex < numWriteFrames; frameIndex++) {
                outBuff[dstSampleIndex++] += data[mCurFrameIndex] * leftGain;
                outBuff[dstSampleIndex++] += data[mCurFrameIndex++] * rightGain;
            }
        }

        if (mCurFrameIndex >= numSampleFrames) {
            mIsPlaying = false;
        }
    }

    // silence
    // no need as the output buffer would need to have been filled with silence
    // to be mixed into
}

} // namespace wavlib