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      1 /*
      2  * Copyright 2014, 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 VIDEO_FRAME_SCHEDULER_H_
     18 #define VIDEO_FRAME_SCHEDULER_H_
     19 
     20 #include <utils/RefBase.h>
     21 #include <utils/Timers.h>
     22 
     23 #include <media/stagefright/foundation/ABase.h>
     24 
     25 namespace android {
     26 
     27 class ISurfaceComposer;
     28 
     29 struct VideoFrameScheduler : public RefBase {
     30     VideoFrameScheduler();
     31 
     32     // (re)initialize scheduler
     33     void init(float videoFps = -1);
     34     // use in case of video render-time discontinuity, e.g. seek
     35     void restart();
     36     // get adjusted nanotime for a video frame render at renderTime
     37     nsecs_t schedule(nsecs_t renderTime);
     38 
     39     // returns the vsync period for the main display
     40     nsecs_t getVsyncPeriod();
     41 
     42     // returns the current frames-per-second, or 0.f if not primed
     43     float getFrameRate();
     44 
     45     void release();
     46 
     47     static const size_t kHistorySize = 8;
     48 
     49 protected:
     50     virtual ~VideoFrameScheduler();
     51 
     52 private:
     53     struct PLL {
     54         PLL();
     55 
     56         // reset PLL to new PLL
     57         void reset(float fps = -1);
     58         // keep current estimate, but restart phase
     59         void restart();
     60         // returns period or 0 if not yet primed
     61         nsecs_t addSample(nsecs_t time);
     62         nsecs_t getPeriod() const;
     63 
     64     private:
     65         nsecs_t mPeriod;
     66         nsecs_t mPhase;
     67 
     68         bool    mPrimed;        // have an estimate for the period
     69         size_t  mSamplesUsedForPriming;
     70 
     71         nsecs_t mLastTime;      // last input time
     72         nsecs_t mRefitAt;       // next input time to fit at
     73 
     74         size_t  mNumSamples;    // can go past kHistorySize
     75         nsecs_t mTimes[kHistorySize];
     76 
     77         void test();
     78         // returns whether fit was successful
     79         bool fit(nsecs_t phase, nsecs_t period, size_t numSamples,
     80                 int64_t *a, int64_t *b, int64_t *err);
     81         void prime(size_t numSamples);
     82     };
     83 
     84     void updateVsync();
     85 
     86     nsecs_t mVsyncTime;        // vsync timing from display
     87     nsecs_t mVsyncPeriod;
     88     nsecs_t mVsyncRefreshAt;   // next time to refresh timing info
     89 
     90     nsecs_t mLastVsyncTime;    // estimated vsync time for last frame
     91     nsecs_t mTimeCorrection;   // running adjustment
     92 
     93     PLL mPll;                  // PLL for video frame rate based on render time
     94 
     95     sp<ISurfaceComposer> mComposer;
     96 
     97     DISALLOW_EVIL_CONSTRUCTORS(VideoFrameScheduler);
     98 };
     99 
    100 }  // namespace android
    101 
    102 #endif  // VIDEO_FRAME_SCHEDULER_H_
    103 
    104