PARP Research Group University of Murcia, Spain


QVYUV4MPEG2CameraWorker Class Reference
[Video and image input/output group]

Class to create YUV4MPEG2 input video reader worker components for the QVision application architecture. More...

#include <qvio/qvyuv4mpeg2cameraworker.h>

Inherits QVCameraWorker.

List of all members.

Public Member Functions

 QVYUV4MPEG2CameraWorker (QString name=QString(""))
 Constructor for QVYUV4MPEG2CameraWorker class.
 ~QVYUV4MPEG2CameraWorker ()

Protected Member Functions

bool openCam (QString urlName, int &cols, int &rows, int &fps)
 Pure virtual openCam method.
void closeCam ()
 Pure virtual closeCam method.
bool grab (QVImage< uChar, 1 > &imgY, QVImage< uChar, 1 > &imgU, QVImage< uChar, 1 > &imgV)
 Pure virtual grab method.
double lengthOfVideo ()
 Pure virtual method to get the length of the video.
double currentPos ()
 Pure virtual method to get the current time position in the video.


Detailed Description

Class to create YUV4MPEG2 input video reader worker components for the QVision application architecture.

This is an implementation of the class QVCameraWorker, which can be used to create video input workers for a QVision application architecture (see QVCameraWorker documentation for more details on generic camera workers). These workers can read image frames from video files stored in the yuv4mpeg2 format.

To use it, create a QVYUV4MPEG2CameraWorker object in the main function, and link a gray image, a RGB image, or three (Y,U,V) one channel images from a worker. For example:

int main(int argc, char *argv[])
        {
        [...]
        // The following worker should have a property named 'Output image' containing a gray (QVImage<uChar>) or 
        // (QVImage<uChar,3>) RGB image:
        MyWorker myWorker("My worker");
        [...]
        QVYUV4MPEG2CameraWorker camera("Input camera");
        camera.linkProperty(&myWorker, "Input image");
        [...]
        }

Alternatively you can link simultaneously three properties containing the Y, U and V channels of a YUV image respectively to store images in the video file directly in that format:

int main(int argc, char *argv[])
        {
        [...]
        // The following worker should have three QVImage<uChar,1> properties named 'Input image Y', 'Input image U',
        // and 'Input image V':
        MyWorker myWorker("My worker");
        [...]
        QVYUV4MPEG2CameraWorker camera("Input camera");
        camera.linkProperty(&myWorker, "Input image Y", "Input image U", "Input image V");
        [...]
        }

Input properties are the following:

  • NoLoop (bool): If the YUV4MPEG2 camera should be opened in no loop mode.
  • RealTime (bool): If the YUV4MPEG2 camera should be opened in real time mode.
  • URL (QString): Name of the video file to read.
  • Cols (int): Number of suggested columns for the video source.
  • Rows (int): Number of suggested rows for the video source.

Note.- RealTime property is also input (and as such can be initialized using the command line), but invisible to the GUI (because once the camera has been linked, it cannot be relinked changing its synchronism).

Note.- Note that you can open the camera in a different size of that specified in the real video source file (this class will automatically rescale output images if needed).

Output properties are the following:

  • Opened (bool): Tells if the camera is correctly opened and working.
  • FPS (int): FPS of the video.
  • Frames (int): Number of read frames up to now.
  • ColsR (int): Actual number of columns of the video -not necessarily equal to the number of requested columns, which will in any case be transparently rounded to the nearest upper even integer-.
  • RowsR (int): Actual number of rows of the video -not necessarily equal to the number of requested rows, which will in any case be transparently rounded to the nearest upper even integer-.
  • Pos (double): Current position in the video (in seconds).
  • Length (double): Length of the video (in seconds).

Note.- Remember that you can open the camera in a different size of that specified in the real video source file (this class will automatically rescale output images if needed); thus, ColsR and RowsR will always contain the real size of the output images served by this worker.

Output image properties:

  • RGB image (QVImage<uChar,3>): Last grabbed RGB image.
  • Y channel image (QVImage<uChar,1>): Last grabbed Y channel image.
  • U channel image (QVImage<uChar,1>): Last grabbed U channel image.
  • V channel image (QVImage<uChar,1>): Last grabbed V channel image.

Output image properties can (and should!) be linked automatically, without the need of naming them explicitly, using any of the QVCameraWorker::linkProperty() available methods.

You can specify any of the input properties at the start of the program, using the command line parameters; for example, the file to read the video from can be specified by calling the program this way: ./program --File="/home/me/myfile.yuv". But modification of these properties can also be done directly in the corresponding graphical widgets when reopening the camera during execution (though, of course, these new values will have no effect until the camera is reopened).

Two important properties are RealTime and NoLoop, both boolean. The first one specifies if the camera will be read in real time mode -possibly leaving frames unprocessed, if processing is slower than reading- (RealTime=true), or at maximum speed -but without leaving any frame unprocessed in any case- (RealTime=false). The second one specifies if the camera will be closed when the end of the file is reached (NoLoop=true), or will loop, starting from the first frame again and again (NoLoop=false).

Definition at line 113 of file qvyuv4mpeg2cameraworker.h.


Constructor & Destructor Documentation

QVYUV4MPEG2CameraWorker::QVYUV4MPEG2CameraWorker ( QString  name = QString("")  )  [inline]

Constructor for QVYUV4MPEG2CameraWorker class.

Parameters:
name the (optional) name given to the camera worker.

Definition at line 119 of file qvyuv4mpeg2cameraworker.h.

QVYUV4MPEG2CameraWorker::~QVYUV4MPEG2CameraWorker (  )  [inline]

Destructor for QVYUV4MPEG2CameraWorker class.

Definition at line 122 of file qvyuv4mpeg2cameraworker.h.


Member Function Documentation

bool QVYUV4MPEG2CameraWorker::openCam ( QString  urlName,
int &  cols,
int &  rows,
int &  fps 
) [protected, virtual]

Pure virtual openCam method.

Reimplementations of this method should open the video source specified by the string urlName, trying to open it with the suggested cols, rows and fps. The method must indicate a successful opening by returning true (and updating the corresponding cols, rows and fps output values to the really obtained ones, which could coincide or not with the suggested input values), or false, if there was any problem opening the source.

Parameters:
urlName QString determining the video source.
cols Suggested number of columns (as input). On return contains real number of columns (as output).
rows Suggested number of rows (as input). On return contains real number of rows (as output).
fps Suggested fps (as input). On return contains real fps (as output).
Returns:
true if success, false if fail.

Implements QVCameraWorker.

Definition at line 30 of file qvyuv4mpeg2cameraworker.cpp.

void QVYUV4MPEG2CameraWorker::closeCam (  )  [protected, virtual]

Pure virtual closeCam method.

Reimplementations of this method should close the video source.

Implements QVCameraWorker.

Definition at line 108 of file qvyuv4mpeg2cameraworker.cpp.

Referenced by ~QVYUV4MPEG2CameraWorker().

bool QVYUV4MPEG2CameraWorker::grab ( QVImage< uChar, 1 > &  imgY,
QVImage< uChar, 1 > &  imgU,
QVImage< uChar, 1 > &  imgV 
) [protected, virtual]

Pure virtual grab method.

Reimplementations of this method should grab Y, U and V channel images in the corresponding variable parameters, with respective sizes cols x rows, cols/2 x rows/2 and cols/2 x rows/2 (with cols and rows as returned by the openCam() method), returning true if grabbing was succesful, or false otherwise (for example, if the camera was closed).

Parameters:
imgY On return, contains the grabbed Y image.
imgU On return, contains the grabbed U image.
imgV On return, contains the grabbed V image.

Implements QVCameraWorker.

Definition at line 113 of file qvyuv4mpeg2cameraworker.cpp.

double QVYUV4MPEG2CameraWorker::lengthOfVideo (  )  [protected, virtual]

Pure virtual method to get the length of the video.

Reimplementations of this method should inform of the length of the video in seconds. A length equal to 0.0 should be returned if not available (for example, for live cameras, remote streaming video, and the like)

Implements QVCameraWorker.

Definition at line 167 of file qvyuv4mpeg2cameraworker.cpp.

double QVYUV4MPEG2CameraWorker::currentPos (  )  [protected, virtual]

Pure virtual method to get the current time position in the video.

Reimplementations of this method should inform of the current position in the video in seconds.

Implements QVCameraWorker.

Definition at line 172 of file qvyuv4mpeg2cameraworker.cpp.


The documentation for this class was generated from the following files:



QVision framework. PARP research group, copyright 2007, 2008.