vpVideoWriter Class Reference

#include <visp3/io/vpVideoWriter.h>

Public Member Functions
	vpVideoWriter ()
virtual	~vpVideoWriter ()
void	close ()
unsigned int	getCurrentFrameIndex () const
std::string	getFrameName () const
void	open (vpImage< vpRGBa > &I)
void	open (vpImage< unsigned char > &I)
void	resetFrameCounter ()
void	saveFrame (vpImage< vpRGBa > &I)
void	saveFrame (vpImage< unsigned char > &I)
void	setCodec (const int fourcc_codec)
void	setFileName (const std::string &filename)
void	setFirstFrameIndex (int first_frame)
void	setFramerate (const double framerate)
void	setFrameStep (const int frame_step)

Detailed Description

Class that enables to write easily a video file or a sequence of images.

This class has its own implementation to write a sequence of PGM and PPM images.

This class may benefit from optional 3rd parties:

• libpng: If installed this optional 3rd party is used to write a sequence of PNG images. Installation instructions are provided here https://visp.inria.fr/3rd_png.
• libjpeg: If installed this optional 3rd party is used to write a sequence of JPEG images. Installation instructions are provided here https://visp.inria.fr/3rd_jpeg.
• OpenCV: If installed this optional 3rd party is used to write a sequence of images where images could be in TIFF, BMP, DIB, PBM, RASTER, JPEG2000 format. If libpng or libjpeg is not installed, OpenCV is also used to consider these image formats. OpenCV allows also to consider AVI, MPEG, MPEG4, MOV, OGV, WMV, FLV, MKV video formats. Installation instructions are provided here https://visp.inria.fr/3rd_opencv.

The following example available in tutorial-video-recorder.cpp shows how this class can be used to record a video from a camera by default in an mpeg file.

 
#include <visp3/core/vpTime.h>
#include <visp3/gui/vpDisplayGDI.h>
#include <visp3/gui/vpDisplayGTK.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/io/vpVideoWriter.h>
#include <visp3/sensor/vpV4l2Grabber.h>
 
#if defined(HAVE_OPENCV_VIDEOIO)
#include <opencv2/videoio.hpp>
#endif
 
int main(int argc, const char *argv [])
{
#if ((defined(VISP_HAVE_V4L2) || defined(HAVE_OPENCV_VIDEOIO)) &&                                            \
     (defined(VISP_HAVE_X11) || defined(VISP_HAVE_GDI) || defined(HAVE_OPENCV_HIGHGUI) || defined(VISP_HAVE_GTK)))
  std::string opt_videoname = "video-recorded.mpg";
  int opt_device = 0;
 
  for (int i = 0; i < argc; i++) {
    if (std::string(argv[i]) == "--device")
      opt_device = atoi(argv[i + 1]);
    else if (std::string(argv[i]) == "--name")
      opt_videoname = std::string(argv[i + 1]);
    else if (std::string(argv[i]) == "--help" || std::string(argv[i]) == "-h") {
      std::cout << "\nUsage: " << argv[0] << " [--device <device number>] [--name <video name>] [--help][-h]\n"
        << std::endl;
      return EXIT_SUCCESS;
    }
  }
 
  std::cout << "Use device: " << opt_device << std::endl;
  std::cout << "Record video in: " << opt_videoname << std::endl;
 
  try {
    // vpImage<vpRGBa> I; // for color images
    vpImage<unsigned char> I; // for gray images
 
#if defined(VISP_HAVE_V4L2)
    vpV4l2Grabber g;
    std::ostringstream device;
    device << "/dev/video" << opt_device;
    g.setDevice(device.str());
    g.setScale(1); // Acquire full resolution images
    g.open(I);
    g.acquire(I);
#elif defined(HAVE_OPENCV_VIDEOIO)
    cv::VideoCapture g(opt_device);
    if (!g.isOpened()) { // check if we succeeded
      std::cout << "Failed to open the camera" << std::endl;
      return EXIT_FAILURE;
    }
    cv::Mat frame;
    g >> frame; // get a new frame from camera
    vpImageConvert::convert(frame, I);
#endif
 
    std::cout << "Image size: " << I.getWidth() << " " << I.getHeight() << std::endl;
 
#if defined(VISP_HAVE_X11)
    vpDisplayX d;
#elif defined(VISP_HAVE_GDI)
    vpDisplayGDI d;
#elif defined(HAVE_OPENCV_HIGHGUI)
    vpDisplayOpenCV d;
#elif defined(VISP_HAVE_GTK)
    vpDisplayGTK d;
#endif
    d.init(I, 0, 0, "Camera view");
    vpVideoWriter writer;
 
#if defined(HAVE_OPENCV_VIDEOIO)
#if (VISP_HAVE_OPENCV_VERSION >= 0x030000)
    writer.setCodec(cv::VideoWriter::fourcc('P', 'I', 'M', '1')); // MPEG-1 codec
#else
    writer.setCodec(CV_FOURCC('P', 'I', 'M', '1'));
#endif
#endif
    writer.setFileName(opt_videoname);
    writer.open(I);
    bool recording = false;
 
    for (;;) {
#if defined(VISP_HAVE_V4L2)
      g.acquire(I);
#elif defined(HAVE_OPENCV_VIDEOIO)
      g >> frame;
      vpImageConvert::convert(frame, I);
#endif
      vpDisplay::display(I);
      if (recording == false) {
        vpDisplay::displayText(I, 10, 10, "A click to start recording", vpColor::green);
        if (vpDisplay::getClick(I, false))
          recording = true;
      }
      else {
        writer.saveFrame(I);
        vpDisplay::displayText(I, 10, 10, "Recording: A click to stop and exit", vpColor::red);
        if (vpDisplay::getClick(I, false))
          break;
      }
 
      vpDisplay::flush(I);
    }
    std::cout << "The video was recorded in \"" << opt_videoname << "\"" << std::endl;
  }
  catch (const vpException &e) {
    std::cout << "Catch an exception: " << e << std::endl;
  }
#else
  (void)argc;
  (void)argv;
  std::cout << "Install OpenCV and rebuild ViSP to use this example." << std::endl;
#endif
  return EXIT_SUCCESS;
}

The following example shows also how this class can be used to write an image sequence. The images are stored in the folder "./image" and are named "image0000.jpeg", "image0001.jpeg", "image0002.jpeg", ...

  #include <visp3/core/vpConfig.h>
  #include <visp3/io/vpVideoWriter.h>
 
int main()
{
  vpImage<vpRGBa> I;
 
  vpVideoWriter writer;
 
  //Initialize the writer.
  writer.setFileName("./image/image%04d.jpeg");
 
  writer.open(I);
 
  for ( ; ; )
  {
    //Here the code to capture or create an image and stores it in I.
 
    //Save the image
    writer.saveFrame(I);
  }
 
  writer.close();
 
  return 0;
 }

The other following example explains how to use the class to write directly an mpeg file.

#include <visp3/io/vpVideoWriter.h>
 
int main()
{
#if defined(VISP_HAVE_OPENCV) && defined(HAVE_OPENCV_VIDEOIO) && defined(HAVE_OPENCV_HIGHGUI)
  vpImage<vpRGBa> I;
 
  vpVideoWriter writer;
 
  // Set up the framerate to 30Hz. Default is 25Hz.
  writer.setFramerate(30);
 
#if VISP_HAVE_OPENCV_VERSION >= 0x030000
  writer.setCodec(cv::VideoWriter::fourcc('P', 'I', 'M', '1'));
#else
  writer.setCodec(CV_FOURCC('P', 'I', 'M', '1'));
#endif
 
  writer.setFileName("./test.mpeg");
 
  writer.open(I);
 
  for (; ; ) {
    // Here the code to capture or create an image and store it in I.
 
    // Save the image
    writer.saveFrame(I);
  }
 
  writer.close();
#endif
  return 0;
}

Examples

grabV4l2MultiCpp11Thread.cpp, readRealSenseData.cpp, servoAfma6MegaposePBVS.cpp, trackMeEllipse.cpp, tutorial-grabber-1394-writer.cpp, tutorial-mb-generic-tracker-full.cpp, tutorial-video-manipulation.cpp, and tutorial-video-recorder.cpp.

Definition at line 153 of file vpVideoWriter.h.

Constructor & Destructor Documentation

vpVideoWriter()

vpVideoWriter::vpVideoWriter

(

)

Basic constructor.

Definition at line 50 of file vpVideoWriter.cpp.

~vpVideoWriter()

vpVideoWriter::~vpVideoWriter ( )

virtual

Basic destructor.

Definition at line 70 of file vpVideoWriter.cpp.

Member Function Documentation

close()

void vpVideoWriter::close

(

)

Deallocates parameters use to write the video or the image sequence.

Examples

tutorial-grabber-1394-writer.cpp.

Definition at line 257 of file vpVideoWriter.cpp.

References vpException::notInitialized.

getCurrentFrameIndex()

unsigned int vpVideoWriter::getCurrentFrameIndex ( ) const

inline

Gets the current frame index.

Returns

Returns the current frame index.

Definition at line 211 of file vpVideoWriter.h.

getFrameName()

std::string vpVideoWriter::getFrameName ( ) const

inline

Return the name of the file in which the last frame was saved.

Examples

tutorial-video-manipulation.cpp.

Definition at line 215 of file vpVideoWriter.h.

open() [1/2]

void vpVideoWriter::open

(

vpImage< unsigned char > &

I

)

Sets all the parameters needed to write the video or the image sequence.

This function will also create recursively the folders to host the video or the sequence of images.

Parameters

I	: One image with the right dimensions.

Definition at line 151 of file vpVideoWriter.cpp.

References vpException::fatalError, vpImage< Type >::getHeight(), vpIoTools::getParent(), vpImage< Type >::getWidth(), vpIoTools::makeDirectory(), and vpImageException::noFileNameError.

open() [2/2]

void vpVideoWriter::open

(

vpImage< vpRGBa > &

I

)

Sets all the parameters needed to write the video or the image sequence.

This function will also create recursively the folders to host the video or the sequence of images.

Parameters

I	: One image with the right dimensions.

Examples

grabV4l2MultiCpp11Thread.cpp, readRealSenseData.cpp, servoAfma6MegaposePBVS.cpp, trackMeEllipse.cpp, tutorial-grabber-1394-writer.cpp, tutorial-mb-generic-tracker-full.cpp, tutorial-video-manipulation.cpp, and tutorial-video-recorder.cpp.

Definition at line 112 of file vpVideoWriter.cpp.

References vpException::fatalError, vpImage< Type >::getHeight(), vpIoTools::getParent(), vpImage< Type >::getWidth(), vpIoTools::makeDirectory(), and vpImageException::noFileNameError.

resetFrameCounter()

void vpVideoWriter::resetFrameCounter ( )

inline

Reset the frame counter and sets it to the first image index.

By default the first frame index is set to 0.

Definition at line 224 of file vpVideoWriter.h.

saveFrame() [1/2]

void vpVideoWriter::saveFrame

(

vpImage< unsigned char > &

I

)

Saves the image as a frame of the video or as an image belonging to the image sequence.

Each time this method is used, the frame counter is incremented and thus the file name change for the case of an image sequence.

Parameters

I	: The image which has to be saved.

Definition at line 223 of file vpVideoWriter.cpp.

References vpImageConvert::convert(), vpException::notInitialized, and vpImageIo::write().

saveFrame() [2/2]

void vpVideoWriter::saveFrame

(

vpImage< vpRGBa > &

I

)

Saves the image as a frame of the video or as an image belonging to the image sequence.

Each time this method is used, the frame counter is incremented and thus the file name change for the case of an image sequence.

Parameters

I	: The image which has to be saved.

Examples

grabV4l2MultiCpp11Thread.cpp, readRealSenseData.cpp, servoAfma6MegaposePBVS.cpp, trackMeEllipse.cpp, tutorial-grabber-1394-writer.cpp, tutorial-mb-generic-tracker-full.cpp, tutorial-video-manipulation.cpp, and tutorial-video-recorder.cpp.

Definition at line 191 of file vpVideoWriter.cpp.

References vpImageConvert::convert(), vpException::notInitialized, and vpImageIo::write().

setCodec()

void vpVideoWriter::setCodec ( const int  fourcc_codec )

inline

Examples

tutorial-video-recorder.cpp.

Definition at line 230 of file vpVideoWriter.h.

setFileName()

void vpVideoWriter::setFileName

(

const std::string &

filename

)

It enables to set the path and the name of the video or sequence of images which will be saved.

If you want to write a sequence of images, filename corresponds to the path followed by the image name template. For exemple, if you want to write different images named image0001.jpeg, image0002.jpg, ... and located in the folder /local/image, filename will be /local/image/image%04d.jpg.

Note

The function open() will create recursively the folders to host the video or the sequence of images.

Parameters

filename

: filename template of an image sequence.

Examples

grabV4l2MultiCpp11Thread.cpp, readRealSenseData.cpp, servoAfma6MegaposePBVS.cpp, trackMeEllipse.cpp, tutorial-grabber-1394-writer.cpp, tutorial-mb-generic-tracker-full.cpp, tutorial-video-manipulation.cpp, and tutorial-video-recorder.cpp.

Definition at line 86 of file vpVideoWriter.cpp.

References vpException::badValue, and vpImageException::noFileNameError.

setFirstFrameIndex()

void vpVideoWriter::setFirstFrameIndex

(

int

first_frame

)

Enables to set the first frame index.

Parameters

first_frame

: The first frame index. Value should be positive.

Examples

tutorial-video-manipulation.cpp.

Definition at line 335 of file vpVideoWriter.cpp.

References vpException::fatalError.

setFramerate()

void vpVideoWriter::setFramerate ( const double  framerate )

inline

Sets the framerate in Hz of the video when encoding.

Parameters

framerate

: The expected framerate.

By default the framerate is set to 25Hz.

Note

Framerate can only be set when OpenCV > 2.1.0.

Definition at line 246 of file vpVideoWriter.h.

setFrameStep()

void vpVideoWriter::setFrameStep ( const int  frame_step )

inline

Set frame step between 2 successive images when a sequence of images is considered.

Parameters

frame_step

: Step between 2 successive images. The default value is 1.

Definition at line 254 of file vpVideoWriter.h.