Visual Servoing Platform  version 3.2.0 under development (2018-08-18)
tutorial-grabber-v4l2-threaded.cpp

[capture-multi-threaded declaration]

#include <iostream>
#include <visp3/core/vpImageConvert.h>
#include <visp3/core/vpMutex.h>
#include <visp3/core/vpThread.h>
#include <visp3/core/vpTime.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/sensor/vpV4l2Grabber.h>
#if defined(VISP_HAVE_V4L2) && defined(VISP_HAVE_PTHREAD)
// Shared vars
typedef enum { capture_waiting, capture_started, capture_stopped } t_CaptureState;
t_CaptureState s_capture_state = capture_waiting;
vpMutex s_mutex_capture;
vpThread::Return captureFunction(vpThread::Args args)
{
vpV4l2Grabber cap = *(static_cast<vpV4l2Grabber *>(args));
bool stop_capture_ = false;
cap.open(frame_);
double start_time = vpTime::measureTimeSecond();
while ((vpTime::measureTimeSecond() - start_time) < 30 && !stop_capture_) {
// Capture in progress
cap.acquire(frame_); // get a new frame from camera
// Update shared data
{
vpMutex::vpScopedLock lock(s_mutex_capture);
if (s_capture_state == capture_stopped)
stop_capture_ = true;
else
s_capture_state = capture_started;
s_frame = frame_;
}
}
{
vpMutex::vpScopedLock lock(s_mutex_capture);
s_capture_state = capture_stopped;
}
std::cout << "End of capture thread" << std::endl;
return 0;
}
vpThread::Return displayFunction(vpThread::Args args)
{
(void)args; // Avoid warning: unused parameter args
t_CaptureState capture_state_;
bool display_initialized_ = false;
#if defined(VISP_HAVE_X11)
vpDisplayX *d_ = NULL;
#endif
do {
s_mutex_capture.lock();
capture_state_ = s_capture_state;
s_mutex_capture.unlock();
// Check if a frame is available
if (capture_state_ == capture_started) {
// Create a copy of the captured frame
{
vpMutex::vpScopedLock lock(s_mutex_capture);
I_ = s_frame;
}
// Check if we need to initialize the display with the first frame
if (!display_initialized_) {
// Initialize the display
#if defined(VISP_HAVE_X11)
d_ = new vpDisplayX(I_);
display_initialized_ = true;
#endif
}
// Display the image
// Trigger end of acquisition with a mouse click
vpDisplay::displayText(I_, 10, 10, "Click to exit...", vpColor::red);
if (vpDisplay::getClick(I_, false)) {
vpMutex::vpScopedLock lock(s_mutex_capture);
s_capture_state = capture_stopped;
}
// Update the display
} else {
vpTime::wait(2); // Sleep 2ms
}
} while (capture_state_ != capture_stopped);
#if defined(VISP_HAVE_X11)
delete d_;
#endif
std::cout << "End of display thread" << std::endl;
return 0;
}
int main(int argc, const char *argv[])
{
unsigned int opt_device = 0; // Default is opening /dev/video0
unsigned int opt_scale = 2; // Default value is 2 in the constructor. Turn
// it to 1 to avoid subsampling
// Command line options
for (int i = 0; i < argc; i++) {
if (std::string(argv[i]) == "--device")
opt_device = (unsigned int)atoi(argv[i + 1]);
else if (std::string(argv[i]) == "--scale")
opt_scale = (unsigned int)atoi(argv[i + 1]);
else if (std::string(argv[i]) == "--help") {
std::cout << "Usage: " << argv[0]
<< " [--device <camera device>] [--scale <subsampling "
"factor>] [--help]"
<< std::endl;
return 0;
}
}
// Instantiate the grabber
std::ostringstream device;
device << "/dev/video" << opt_device;
g.setDevice(device.str());
g.setScale(opt_scale);
// Start the threads
vpThread thread_capture((vpThread::Fn)captureFunction, (vpThread::Args)&g);
vpThread thread_display((vpThread::Fn)displayFunction);
// Wait until thread ends up
thread_capture.join();
thread_display.join();
return 0;
}
#else
int main()
{
#ifndef VISP_HAVE_V4L2
std::cout << "You should enable V4L2 to make this example working..." << std::endl;
#elif !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
std::cout << "You should enable pthread usage and rebuild ViSP..." << std::endl;
#else
std::cout << "Multi-threading seems not supported on this platform" << std::endl;
#endif
}
#endif