Visual Servoing Platform  version 3.2.1 under development (2019-07-16)
tutorial-grabber-v4l2-threaded.cpp
1 #include <iostream>
4 
5 #include <visp3/core/vpImageConvert.h>
6 #include <visp3/core/vpMutex.h>
7 #include <visp3/core/vpThread.h>
8 #include <visp3/core/vpTime.h>
9 #include <visp3/gui/vpDisplayX.h>
10 #include <visp3/sensor/vpV4l2Grabber.h>
11 
12 #if defined(VISP_HAVE_V4L2) && defined(VISP_HAVE_PTHREAD)
13 
14 // Shared vars
15 typedef enum { capture_waiting, capture_started, capture_stopped } t_CaptureState;
16 t_CaptureState s_capture_state = capture_waiting;
18 vpMutex s_mutex_capture;
20 
22 vpThread::Return captureFunction(vpThread::Args args)
23 {
24  vpV4l2Grabber cap = *(static_cast<vpV4l2Grabber *>(args));
26  bool stop_capture_ = false;
27 
28  cap.open(frame_);
29 
30  double start_time = vpTime::measureTimeSecond();
31  while ((vpTime::measureTimeSecond() - start_time) < 30 && !stop_capture_) {
32  // Capture in progress
33  cap.acquire(frame_); // get a new frame from camera
34 
35  // Update shared data
36  {
37  vpMutex::vpScopedLock lock(s_mutex_capture);
38  if (s_capture_state == capture_stopped)
39  stop_capture_ = true;
40  else
41  s_capture_state = capture_started;
42  s_frame = frame_;
43  }
44  }
45 
46  {
47  vpMutex::vpScopedLock lock(s_mutex_capture);
48  s_capture_state = capture_stopped;
49  }
50  std::cout << "End of capture thread" << std::endl;
51  return 0;
52 }
54 
56 vpThread::Return displayFunction(vpThread::Args args)
57 {
58  (void)args; // Avoid warning: unused parameter args
60 
61  t_CaptureState capture_state_;
62  bool display_initialized_ = false;
63 #if defined(VISP_HAVE_X11)
64  vpDisplayX *d_ = NULL;
65 #endif
66 
67  do {
68  s_mutex_capture.lock();
69  capture_state_ = s_capture_state;
70  s_mutex_capture.unlock();
71 
72  // Check if a frame is available
73  if (capture_state_ == capture_started) {
74  // Create a copy of the captured frame
75  {
76  vpMutex::vpScopedLock lock(s_mutex_capture);
77  I_ = s_frame;
78  }
79 
80  // Check if we need to initialize the display with the first frame
81  if (!display_initialized_) {
82 // Initialize the display
83 #if defined(VISP_HAVE_X11)
84  d_ = new vpDisplayX(I_);
85  display_initialized_ = true;
86 #endif
87  }
88 
89  // Display the image
91 
92  // Trigger end of acquisition with a mouse click
93  vpDisplay::displayText(I_, 10, 10, "Click to exit...", vpColor::red);
94  if (vpDisplay::getClick(I_, false)) {
95  vpMutex::vpScopedLock lock(s_mutex_capture);
96  s_capture_state = capture_stopped;
97  }
98 
99  // Update the display
100  vpDisplay::flush(I_);
101  } else {
102  vpTime::wait(2); // Sleep 2ms
103  }
104  } while (capture_state_ != capture_stopped);
105 
106 #if defined(VISP_HAVE_X11)
107  delete d_;
108 #endif
109 
110  std::cout << "End of display thread" << std::endl;
111  return 0;
112 }
114 
116 int main(int argc, const char *argv[])
117 {
118  unsigned int opt_device = 0; // Default is opening /dev/video0
119  unsigned int opt_scale = 2; // Default value is 2 in the constructor. Turn
120  // it to 1 to avoid subsampling
121 
122  // Command line options
123  for (int i = 0; i < argc; i++) {
124  if (std::string(argv[i]) == "--camera_device")
125  opt_device = (unsigned int)atoi(argv[i + 1]);
126  else if (std::string(argv[i]) == "--scale")
127  opt_scale = (unsigned int)atoi(argv[i + 1]);
128  else if (std::string(argv[i]) == "--help" || std::string(argv[i]) == "--h") {
129  std::cout << "Usage: " << argv[0]
130  << " [--camera_device <camera device (default: 0)>] [--scale <subsampling factor>]"
131  << " [--help] [-h]"
132  << std::endl;
133  return 0;
134  }
135  }
136 
137  // Instantiate the grabber
138  vpV4l2Grabber g;
139  std::ostringstream device;
140  device << "/dev/video" << opt_device;
141  g.setDevice(device.str());
142  g.setScale(opt_scale);
143 
144  // Start the threads
145  vpThread thread_capture((vpThread::Fn)captureFunction, (vpThread::Args)&g);
146  vpThread thread_display((vpThread::Fn)displayFunction);
147 
148  // Wait until thread ends up
149  thread_capture.join();
150  thread_display.join();
151 
152  return 0;
153 }
155 
156 #else
157 int main()
158 {
159 #ifndef VISP_HAVE_V4L2
160  std::cout << "You should enable V4L2 to make this example working..." << std::endl;
161 #elif !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
162  std::cout << "You should enable pthread usage and rebuild ViSP..." << std::endl;
163 #else
164  std::cout << "Multi-threading seems not supported on this platform" << std::endl;
165 #endif
166 }
167 
168 #endif
Class that allows protection by mutex.
Definition: vpMutex.h:170
VISP_EXPORT int wait(double t0, double t)
Definition: vpTime.cpp:150
void acquire(vpImage< unsigned char > &I)
void lock()
Definition: vpMutex.h:95
static bool getClick(const vpImage< unsigned char > &I, bool blocking=true)
void open(vpImage< unsigned char > &I)
void * Return
Definition: vpThread.h:78
VISP_EXPORT double measureTimeSecond()
Definition: vpTime.cpp:250
static void displayText(const vpImage< unsigned char > &I, const vpImagePoint &ip, const std::string &s, const vpColor &color)
void unlock()
Definition: vpMutex.h:111
Use the X11 console to display images on unix-like OS. Thus to enable this class X11 should be instal...
Definition: vpDisplayX.h:151
void setDevice(const std::string &devname)
static void flush(const vpImage< unsigned char > &I)
static const vpColor red
Definition: vpColor.h:180
void *(* Fn)(Args)
Definition: vpThread.h:79
void * Args
Definition: vpThread.h:77
static void display(const vpImage< unsigned char > &I)
void setScale(unsigned scale=vpV4l2Grabber::DEFAULT_SCALE)
Class that is a wrapper over the Video4Linux2 (V4L2) driver.