![]() |
University of Murcia, Spain ![]() |
QVMPlayerCameraWorker Class ReferenceClass to create MPlayer input video reader worker components for the QVision application architecture.
More...
|
Public Member Functions | |
QVMPlayerCameraWorker (QString name) | |
Constructor for QVMPlayerCameraWorker class. | |
~QVMPlayerCameraWorker () | |
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. |
This is an implementation of the class QVCameraWorker based on the QVMPlayerReader interface class for the MPlayer application (see QVCameraWorker documentation for more details on generic camera workers). Specifically, this mplayer camera worker can create input workers to read frames from a video source, in a QVision application. The video sources can be any video file or device connected physically to the computer, or remotely through a network video stream. The class can read from a wide variety of media formats.
For a detailed usage of this class in a QVision application, see section ProgrammingModel. To learn how to specify a given video source for the class, read QVMPlayerReader class documentation. Specifically, the Video source identifier URL formats section.
To use it, create a QVMPlayerCameraWorker 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"); [...] QVMPlayerCameraWorker camera("Input camera"); camera.linkProperty(&myWorker, "Input image"); [...] }
Alternatively you can link simultaneously three properties containing the Y, U and V channels of the images grabbed by the camera:
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"); [...] QVMPlayerCameraWorker camera("Input camera"); camera.linkProperty(&myWorker, "Input image Y", "Input image U", "Input image V"); [...] }
Input properties are the following:
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:
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:
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.avi". 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 120 of file qvmplayercameraworker.h.
QVMPlayerCameraWorker::QVMPlayerCameraWorker | ( | QString | name | ) |
Constructor for QVMPlayerCameraWorker class.
name | the (optional) name given to the camera worker. |
Definition at line 31 of file qvmplayercameraworker.cpp.
QVMPlayerCameraWorker::~QVMPlayerCameraWorker | ( | ) | [inline] |
Destructor for QVMPlayerCameraWorker class.
Definition at line 129 of file qvmplayercameraworker.h.
bool QVMPlayerCameraWorker::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.
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). |
Implements QVCameraWorker.
Definition at line 38 of file qvmplayercameraworker.cpp.
void QVMPlayerCameraWorker::closeCam | ( | ) | [protected, virtual] |
Pure virtual closeCam method.
Reimplementations of this method should close the video source.
Implements QVCameraWorker.
Definition at line 68 of file qvmplayercameraworker.cpp.
bool QVMPlayerCameraWorker::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).
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 73 of file qvmplayercameraworker.cpp.
double QVMPlayerCameraWorker::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 78 of file qvmplayercameraworker.cpp.
double QVMPlayerCameraWorker::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 83 of file qvmplayercameraworker.cpp.