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      1 /*
      2  * Copyright (C) 2016 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 #ifndef ANDROID_AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
     18 #define ANDROID_AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
     19 
     20 #include <stdint.h>
     21 
     22 namespace aaudio {
     23 
     24 /**
     25  * Model an isochronous data stream using occasional timestamps as input.
     26  * This can be used to predict the position of the stream at a given time.
     27  *
     28  * This class is not thread safe and should only be called from one thread.
     29  */
     30 class IsochronousClockModel {
     31 
     32 public:
     33     IsochronousClockModel();
     34     virtual ~IsochronousClockModel();
     35 
     36     void start(int64_t nanoTime);
     37     void stop(int64_t nanoTime);
     38 
     39     bool isStarting();
     40 
     41     void processTimestamp(int64_t framePosition, int64_t nanoTime);
     42 
     43     /**
     44      * @param sampleRate rate of the stream in frames per second
     45      */
     46     void setSampleRate(int32_t sampleRate);
     47 
     48     void setPositionAndTime(int64_t framePosition, int64_t nanoTime);
     49 
     50     int32_t getSampleRate() const {
     51         return mSampleRate;
     52     }
     53 
     54     /**
     55      * This must be set accurately in order to track the isochronous stream.
     56      *
     57      * @param framesPerBurst number of frames that stream advance at one time.
     58      */
     59     void setFramesPerBurst(int32_t framesPerBurst);
     60 
     61     int32_t getFramesPerBurst() const {
     62         return mFramesPerBurst;
     63     }
     64 
     65     /**
     66      * Calculate an estimated time when the stream will be at that position.
     67      *
     68      * @param framePosition position of the stream in frames
     69      * @return time in nanoseconds
     70      */
     71     int64_t convertPositionToTime(int64_t framePosition) const;
     72 
     73     /**
     74      * Calculate an estimated position where the stream will be at the specified time.
     75      *
     76      * @param nanoTime time of interest
     77      * @return position in frames
     78      */
     79     int64_t convertTimeToPosition(int64_t nanoTime) const;
     80 
     81     /**
     82      * @param framesDelta difference in frames
     83      * @return duration in nanoseconds
     84      */
     85     int64_t convertDeltaPositionToTime(int64_t framesDelta) const;
     86 
     87     /**
     88      * @param nanosDelta duration in nanoseconds
     89      * @return frames that stream will advance in that time
     90      */
     91     int64_t convertDeltaTimeToPosition(int64_t nanosDelta) const;
     92 
     93     void dump() const;
     94 
     95 private:
     96     enum clock_model_state_t {
     97         STATE_STOPPED,
     98         STATE_STARTING,
     99         STATE_SYNCING,
    100         STATE_RUNNING
    101     };
    102 
    103     int64_t             mMarkerFramePosition;
    104     int64_t             mMarkerNanoTime;
    105     int32_t             mSampleRate;
    106     int32_t             mFramesPerBurst;
    107     int32_t             mMaxLatenessInNanos;
    108     clock_model_state_t mState;
    109 
    110     void update();
    111 };
    112 
    113 } /* namespace aaudio */
    114 
    115 #endif //ANDROID_AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
    116