media/libaaudio/src/client/IsochronousClockModel.h

/*
 * Copyright (C) 2016 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.
 */

#ifndef AAUDIO_ISOCHRONOUSCLOCKMODEL_H
#define AAUDIO_ISOCHRONOUSCLOCKMODEL_H

#include <stdint.h>
#include <aaudio/AAudio.h>

namespace aaudio {

/**
 * Model an isochronous data stream using occasional timestamps as input.
 * This can be used to predict the position of the stream at a given time.
 *
 * This class is not thread safe and should only be called from one thread.
 */
class IsochronousClockModel {

public:
    IsochronousClockModel();
    virtual ~IsochronousClockModel();

    void start(int64_t nanoTime);
    void stop(int64_t nanoTime);

    void processTimestamp(int64_t framePosition, int64_t nanoTime);

    /**
     * @param sampleRate rate of the stream in frames per second
     */
    void setSampleRate(int32_t sampleRate);

    int32_t getSampleRate() const {
        return mSampleRate;
    }

    /**
     * This must be set accurately in order to track the isochronous stream.
     *
     * @param framesPerBurst number of frames that stream advance at one time.
     */
    void setFramesPerBurst(int32_t framesPerBurst);

    int32_t getFramesPerBurst() const {
        return mFramesPerBurst;
    }

    /**
     * Calculate an estimated time when the stream will be at that position.
     *
     * @param framePosition position of the stream in frames
     * @return time in nanoseconds
     */
    int64_t convertPositionToTime(int64_t framePosition) const;

    /**
     * Calculate an estimated position where the stream will be at the specified time.
     *
     * @param nanoTime time of interest
     * @return position in frames
     */
    int64_t convertTimeToPosition(int64_t nanoTime) const;

    /**
     * @param framesDelta difference in frames
     * @return duration in nanoseconds
     */
    int64_t convertDeltaPositionToTime(int64_t framesDelta) const;

    /**
     * @param nanosDelta duration in nanoseconds
     * @return frames that stream will advance in that time
     */
    int64_t convertDeltaTimeToPosition(int64_t nanosDelta) const;

private:
    enum clock_model_state_t {
        STATE_STOPPED,
        STATE_STARTING,
        STATE_SYNCING,
        STATE_RUNNING
    };

    int64_t             mMarkerFramePosition;
    int64_t             mMarkerNanoTime;
    int32_t             mSampleRate;
    int32_t             mFramesPerBurst;
    int32_t             mMaxLatenessInNanos;
    clock_model_state_t mState;

    void update();
};

} /* namespace aaudio */

#endif //AAUDIO_ISOCHRONOUSCLOCKMODEL_H