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