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vpVideoWriter Class Reference
Video I/O

#include <visp3/io/vpVideoWriter.h>

Public Member Functions

 vpVideoWriter ()
 
 ~vpVideoWriter ()
 
void close ()
 
unsigned int getCurrentFrameIndex () 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 setBitRate (const unsigned int bitrate)
 
void setCodec (const AVCodecID codec_id)
 
void setFileName (const char *filename)
 
void setFileName (const std::string &filename)
 
void setFirstFrameIndex (const unsigned int first_frame)
 
void setFramerate (const int frame_rate)
 

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.
  • ffmpeg: If installed and enabled this optional 3rd party is used to write AVI, MPEG, MPEG4, MOV, OGV, WMV, FLV, MKV video formats. It means that if OpenCV is also installed, that OpenCV is not used to read a video. Installation instructions are provided here https://visp.inria.fr/3rd_ffmpeg.

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/gui/vpDisplayGDI.h>
#include <visp3/gui/vpDisplayGTK.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/core/vpTime.h>
#include <visp3/io/vpVideoWriter.h>
#include <visp3/sensor/vpV4l2Grabber.h>
int main(int argc, const char *argv[])
{
#if ((defined(VISP_HAVE_V4L2) || (VISP_HAVE_OPENCV_VERSION >= 0x020100)) && (defined(VISP_HAVE_X11) || defined(VISP_HAVE_GDI) || defined(VISP_HAVE_OPENCV) || 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::cout << "\nUsage: " << argv[0] << " [--device <device number>] [--name <video name>] [--help]\n" << std::endl;
return 0;
}
}
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.open(I);
g.acquire(I);
#elif defined(VISP_HAVE_OPENCV)
cv::VideoCapture g(opt_device);
if(!g.isOpened()) { // check if we succeeded
std::cout << "Failed to open the camera" << std::endl;
return -1;
}
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(VISP_HAVE_OPENCV)
vpDisplayOpenCV d;
#elif defined(VISP_HAVE_GTK)
vpDisplayGTK d;
#endif
d.init(I, 0, 0, "Camera view");
vpVideoWriter writer;
#ifdef VISP_HAVE_FFMPEG
// Set up the bit rate
writer.setBitRate(1000000);
// Set up the codec to use
# if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(54,51,110) // libavcodec 54.51.100
writer.setCodec(CODEC_ID_MPEG2VIDEO);
# else
writer.setCodec(AV_CODEC_ID_MPEG2VIDEO);
# endif
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
writer.setCodec( cv::VideoWriter::fourcc('P','I','M','1') ); // MPEG-1 codec
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
writer.setCodec( CV_FOURCC('P','I','M','1') );
#endif
writer.setFileName(opt_videoname);
writer.open(I);
bool recording = false;
for(;;) {
#if defined(VISP_HAVE_V4L2)
g.acquire(I);
#elif defined(VISP_HAVE_OPENCV)
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(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
}

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()
{
vpImage<vpRGBa> I;
vpVideoWriter writer;
// Set up the framerate to 30Hz. Default is 25Hz.
writer.setFramerate(30);
#ifdef VISP_HAVE_FFMPEG
// Set up the bit rate
writer.setBitRate(1000000);
// Set up the codec to use
#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(54,51,110) // libavcodec 54.51.100
writer.setCodec(CODEC_ID_MPEG2VIDEO);
#else
writer.setCodec(AV_CODEC_ID_MPEG2VIDEO);
#endif
#elif defined VISP_HAVE_OPENCV
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();
return 0;
}
Examples:
grabV4l2MultiCpp11Thread.cpp, tutorial-grabber-1394-writer.cpp, and tutorial-video-recorder.cpp.

Definition at line 163 of file vpVideoWriter.h.

Constructor & Destructor Documentation

vpVideoWriter::vpVideoWriter ( )

Basic constructor.

Definition at line 55 of file vpVideoWriter.cpp.

vpVideoWriter::~vpVideoWriter ( )

Basic destructor.

Definition at line 98 of file vpVideoWriter.cpp.

Member Function Documentation

void vpVideoWriter::close ( )

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

Examples:
tutorial-grabber-1394-writer.cpp.

Definition at line 348 of file vpVideoWriter.cpp.

References vpFFMPEG::endWrite(), vpException::notInitialized, and vpERROR_TRACE.

unsigned int vpVideoWriter::getCurrentFrameIndex ( ) const
inline

Gets the current frame index.

Returns
Returns the current frame index.

Definition at line 230 of file vpVideoWriter.h.

void vpVideoWriter::open ( vpImage< vpRGBa > &  I)

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

Parameters
I: One image with the right dimensions.
Examples:
grabV4l2MultiCpp11Thread.cpp, tutorial-grabber-1394-writer.cpp, and tutorial-video-recorder.cpp.

Definition at line 155 of file vpVideoWriter.cpp.

References vpException::fatalError, vpImage< Type >::getHeight(), vpImage< Type >::getWidth(), vpException::ioError, vpImageException::noFileNameError, vpFFMPEG::openEncoder(), vpFFMPEG::setBitRate(), vpFFMPEG::setFramerate(), and vpERROR_TRACE.

void vpVideoWriter::open ( vpImage< unsigned char > &  I)

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

Parameters
I: One image with the right dimensions.

Definition at line 208 of file vpVideoWriter.cpp.

References vpException::fatalError, vpImage< Type >::getHeight(), vpImage< Type >::getWidth(), vpException::ioError, vpImageException::noFileNameError, vpFFMPEG::openEncoder(), vpFFMPEG::setBitRate(), vpFFMPEG::setFramerate(), and vpERROR_TRACE.

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 239 of file vpVideoWriter.h.

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, tutorial-grabber-1394-writer.cpp, and tutorial-video-recorder.cpp.

Definition at line 263 of file vpVideoWriter.cpp.

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

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 305 of file vpVideoWriter.cpp.

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

void vpVideoWriter::setBitRate ( const unsigned int  bitrate)
inline

Sets the bit rate of the video when encoding.

Parameters
bitrate: the expected bit rate.

By default the bit rate is set to 500 000.

Examples:
tutorial-video-recorder.cpp.

Definition at line 252 of file vpVideoWriter.h.

void vpVideoWriter::setCodec ( const AVCodecID  codec_id)
inline

Sets the codec used to encode the video.

Parameters
codec_id: the expected codec.

By default codec is set to AV_CODEC_ID_MPEG1VIDEO. But if installed, you can use one of the AVCodecID proposed by ffmpeg such as : AV_CODEC_ID_MPEG2VIDEO, AV_CODEC_ID_MPEG2VIDEO_XVMC, AV_CODEC_ID_MPEG4, AV_CODEC_ID_H264, ... (More AVCodecID can be found in the ffmpeg documentation).

Of course to use the codec it must be installed on your computer.

Examples:
tutorial-video-recorder.cpp.

Definition at line 268 of file vpVideoWriter.h.

void vpVideoWriter::setFileName ( const char *  filename)

It enables to set the path and the name of the files 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".

Parameters
filename: filename template of an image sequence.
Examples:
grabV4l2MultiCpp11Thread.cpp, tutorial-grabber-1394-writer.cpp, and tutorial-video-recorder.cpp.

Definition at line 114 of file vpVideoWriter.cpp.

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

Referenced by setFileName().

void vpVideoWriter::setFileName ( const std::string &  filename)

It enables to set the path and the name of the files 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".

Parameters
filename: filename template of an image sequence.

Definition at line 145 of file vpVideoWriter.cpp.

References setFileName().

void vpVideoWriter::setFirstFrameIndex ( const unsigned int  first_frame)
inline

Enables to set the first frame index.

Parameters
first_frame: The first frame index.

Definition at line 281 of file vpVideoWriter.h.

void vpVideoWriter::setFramerate ( const int  frame_rate)
inline

Sets the framerate in Hz of the video when encoding.

Parameters
frame_rate: the expected framerate.

By default the framerate is set to 25Hz.

Definition at line 290 of file vpVideoWriter.h.