1 /*
2  * Copyright (C) 2012 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 /**
18  * This class is a simple simulation of a typical CMOS cellphone imager chip,
19  * which outputs 12-bit Bayer-mosaic raw images.
20  *
21  * Unlike most real image sensors, this one's native color space is linear sRGB.
22  *
23  * The sensor is abstracted as operating as a pipeline 3 stages deep;
24  * conceptually, each frame to be captured goes through these three stages. The
25  * processing step for the sensor is marked off by vertical sync signals, which
26  * indicate the start of readout of the oldest frame. The interval between
27  * processing steps depends on the frame duration of the frame currently being
28  * captured. The stages are 1) configure, 2) capture, and 3) readout. During
29  * configuration, the sensor's registers for settings such as exposure time,
30  * frame duration, and gain are set for the next frame to be captured. In stage
31  * 2, the image data for the frame is actually captured by the sensor. Finally,
32  * in stage 3, the just-captured data is read out and sent to the rest of the
33  * system.
34  *
35  * The sensor is assumed to be rolling-shutter, so low-numbered rows of the
36  * sensor are exposed earlier in time than larger-numbered rows, with the time
37  * offset between each row being equal to the row readout time.
38  *
39  * The characteristics of this sensor don't correspond to any actual sensor,
40  * but are not far off typical sensors.
41  *
42  * Example timing diagram, with three frames:
43  *  Frame 0-1: Frame duration 50 ms, exposure time 20 ms.
44  *  Frame   2: Frame duration 75 ms, exposure time 65 ms.
45  * Legend:
46  *   C = update sensor registers for frame
47  *   v = row in reset (vertical blanking interval)
48  *   E = row capturing image data
49  *   R = row being read out
50  *   | = vertical sync signal
51  *time(ms)|   0          55        105       155            230     270
52  * Frame 0|   :configure : capture : readout :              :       :
53  *  Row # | ..|CCCC______|_________|_________|              :       :
54  *      0 |   :\          \vvvvvEEEER         \             :       :
55  *    500 |   : \          \vvvvvEEEER         \            :       :
56  *   1000 |   :  \          \vvvvvEEEER         \           :       :
57  *   1500 |   :   \          \vvvvvEEEER         \          :       :
58  *   2000 |   :    \__________\vvvvvEEEER_________\         :       :
59  * Frame 1|   :           configure  capture      readout   :       :
60  *  Row # |   :          |CCCC_____|_________|______________|       :
61  *      0 |   :          :\         \vvvvvEEEER              \      :
62  *    500 |   :          : \         \vvvvvEEEER              \     :
63  *   1000 |   :          :  \         \vvvvvEEEER              \    :
64  *   1500 |   :          :   \         \vvvvvEEEER              \   :
65  *   2000 |   :          :    \_________\vvvvvEEEER______________\  :
66  * Frame 2|   :          :          configure     capture    readout:
67  *  Row # |   :          :         |CCCC_____|______________|_______|...
68  *      0 |   :          :         :\         \vEEEEEEEEEEEEER       \
69  *    500 |   :          :         : \         \vEEEEEEEEEEEEER       \
70  *   1000 |   :          :         :  \         \vEEEEEEEEEEEEER       \
71  *   1500 |   :          :         :   \         \vEEEEEEEEEEEEER       \
72  *   2000 |   :          :         :    \_________\vEEEEEEEEEEEEER_______\
73  */
74 
75 #ifndef HW_EMULATOR_CAMERA2_SENSOR_H
76 #define HW_EMULATOR_CAMERA2_SENSOR_H
77 
78 #include "utils/Thread.h"
79 #include "utils/Mutex.h"
80 #include "utils/Timers.h"
81 
82 #include "Scene.h"
83 #include "Base.h"
84 
85 namespace android {
86 
87 class EmulatedFakeCamera2;
88 
89 class Sensor: private Thread, public virtual RefBase {
90   public:
91 
92     Sensor();
93     ~Sensor();
94 
95     /*
96      * Power control
97      */
98 
99     status_t startUp();
100     status_t shutDown();
101 
102     /*
103      * Access to scene
104      */
105     Scene &getScene();
106 
107     /*
108      * Controls that can be updated every frame
109      */
110 
111     void setExposureTime(uint64_t ns);
112     void setFrameDuration(uint64_t ns);
113     void setSensitivity(uint32_t gain);
114     // Buffer must be at least stride*height*2 bytes in size
115     void setDestinationBuffers(Buffers *buffers);
116     // To simplify tracking sensor's current frame
117     void setFrameNumber(uint32_t frameNumber);
118 
119     /*
120      * Controls that cause reconfiguration delay
121      */
122 
123     void setBinning(int horizontalFactor, int verticalFactor);
124 
125     /*
126      * Synchronizing with sensor operation (vertical sync)
127      */
128 
129     // Wait until the sensor outputs its next vertical sync signal, meaning it
130     // is starting readout of its latest frame of data. Returns true if vertical
131     // sync is signaled, false if the wait timed out.
132     bool waitForVSync(nsecs_t reltime);
133 
134     // Wait until a new frame has been read out, and then return the time
135     // capture started.  May return immediately if a new frame has been pushed
136     // since the last wait for a new frame. Returns true if new frame is
137     // returned, false if timed out.
138     bool waitForNewFrame(nsecs_t reltime,
139             nsecs_t *captureTime);
140 
141     /*
142      * Interrupt event servicing from the sensor. Only triggers for sensor
143      * cycles that have valid buffers to write to.
144      */
145     struct SensorListener {
146         enum Event {
147             EXPOSURE_START, // Start of exposure
148         };
149 
150         virtual void onSensorEvent(uint32_t frameNumber, Event e,
151                 nsecs_t timestamp) = 0;
152         virtual ~SensorListener();
153     };
154 
155     void setSensorListener(SensorListener *listener);
156 
157     /**
158      * Static sensor characteristics
159      */
160     static const unsigned int kResolution[2];
161 
162     static const nsecs_t kExposureTimeRange[2];
163     static const nsecs_t kFrameDurationRange[2];
164     static const nsecs_t kMinVerticalBlank;
165 
166     static const uint8_t kColorFilterArrangement;
167 
168     // Output image data characteristics
169     static const uint32_t kMaxRawValue;
170     static const uint32_t kBlackLevel;
171     // Sensor sensitivity, approximate
172 
173     static const float kSaturationVoltage;
174     static const uint32_t kSaturationElectrons;
175     static const float kVoltsPerLuxSecond;
176     static const float kElectronsPerLuxSecond;
177 
178     static const float kBaseGainFactor;
179 
180     static const float kReadNoiseStddevBeforeGain; // In electrons
181     static const float kReadNoiseStddevAfterGain;  // In raw digital units
182     static const float kReadNoiseVarBeforeGain;
183     static const float kReadNoiseVarAfterGain;
184 
185     // While each row has to read out, reset, and then expose, the (reset +
186     // expose) sequence can be overlapped by other row readouts, so the final
187     // minimum frame duration is purely a function of row readout time, at least
188     // if there's a reasonable number of rows.
189     static const nsecs_t kRowReadoutTime;
190 
191     static const int32_t kSensitivityRange[2];
192     static const uint32_t kDefaultSensitivity;
193 
194   private:
195     Mutex mControlMutex; // Lock before accessing control parameters
196     // Start of control parameters
197     Condition mVSync;
198     bool      mGotVSync;
199     uint64_t  mExposureTime;
200     uint64_t  mFrameDuration;
201     uint32_t  mGainFactor;
202     Buffers  *mNextBuffers;
203     uint32_t  mFrameNumber;
204 
205     // End of control parameters
206 
207     Mutex mReadoutMutex; // Lock before accessing readout variables
208     // Start of readout variables
209     Condition mReadoutAvailable;
210     Condition mReadoutComplete;
211     Buffers  *mCapturedBuffers;
212     nsecs_t   mCaptureTime;
213     SensorListener *mListener;
214     // End of readout variables
215 
216     // Time of sensor startup, used for simulation zero-time point
217     nsecs_t mStartupTime;
218 
219     /**
220      * Inherited Thread virtual overrides, and members only used by the
221      * processing thread
222      */
223   private:
224     virtual status_t readyToRun();
225 
226     virtual bool threadLoop();
227 
228     nsecs_t mNextCaptureTime;
229     Buffers *mNextCapturedBuffers;
230 
231     Scene mScene;
232 
233     void captureRaw(uint8_t *img, uint32_t gain, uint32_t stride);
234     void captureRGBA(uint8_t *img, uint32_t gain, uint32_t stride);
235     void captureRGB(uint8_t *img, uint32_t gain, uint32_t stride);
236     void captureNV21(uint8_t *img, uint32_t gain, uint32_t stride);
237 };
238 
239 }
240 
241 #endif // HW_EMULATOR_CAMERA2_SENSOR_H
242