![]() |
University of Murcia ![]() |
QVVideoReaderBlock Class ReferenceVirtual base class to create input video reader block components for the QVision application architecture.
More...
|
Public Types | |
enum | TCameraStatus { , Running, RunningOneStep, Paused } |
Camera status. | |
enum | TSeekType |
Options for a seek through the file. | |
Signals | |
void | opened () |
Emitted each time a new video source is opened. | |
void | closed () |
Emitted each time the video source is closed. | |
void | grabbed () |
Emitted each time a new frame is grabbed. | |
Public Member Functions | |
QVVideoReaderBlock (QString name=QString("")) | |
Constructor for (virtual) QVVideoReaderBlock class. | |
~QVVideoReaderBlock () | |
Destructor for (virtual) QVVideoReaderBlock class. | |
bool | linkProperty (QVPropertyContainer *dstCont, QString dstProp) |
Links a QVImage<uChar,3> or QVImage<uChar,1> from the camera to another block. | |
bool | linkProperty (QVPropertyContainer *dstCont, QString dstProp1, QString dstProp2, QString dstProp3) |
Links 3 QVImage<uChar,1> from the camera (YUV channels) to the corresponding ones of another block. | |
Protected Member Functions | |
virtual bool | open (QString urlName, int &cols, int &rows, int &fps)=0 |
Pure virtual open method. | |
virtual void | close ()=0 |
Pure virtual close method. | |
virtual bool | grab (QVImage< uChar, 1 > &imgY, QVImage< uChar, 1 > &imgU, QVImage< uChar, 1 > &imgV)=0 |
Pure virtual grab method. | |
virtual double | lengthOfVideo ()=0 |
Pure virtual method to get the length of the video. | |
virtual double | currentPos ()=0 |
Pure virtual method to get the current time position in the video. |
This class is pure virtual, and should not be used by normal QVision users (except when implementing their own video sources blocks, such as, say, direct driver-based IEEE 1394 or V4L2 cameras; remember, though, that QVMPlayerReaderBlock can read almost any kind of video input source, including live cameras, such as webcams, DV cameras, and so on). Any of its two derived classes QVYUV4MPEG2ReaderBlock and QVMPlayerReaderBlock are the classes that normal users will use. See documentation on those classes for more details.
Implementors of new kind of QVVideoReaderBlocks should only have to redefine this five pure virtual methods:
Whose desired behaviour should be self-explanatory: the first one should open the video source specified by the string urlName, trying to open it with the suggested cols, rows and fps. The method must indicates 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. The second must close the video source. The third must 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 open method), returning true if grabbing was succesful, or false otherwise (for example, if the camera was closed). The fourth method must return the length of the video in seconds (or 0.0 if not available; for example, for live video cameras). Finally, the fifth method must return, when called, the current position in the video, again in seconds.
All camera blocks inheriting from this class will always have the following properties:
Input properties:
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, by setting the desired values of properties Cols and Rows (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 block.
Output image properties:
Output image properties can (and should!) be linked automatically, without the need of naming them explicitly, using any of the QVVideoReaderBlock::linkProperty() available methods.
Definition at line 86 of file qvvideoreaderblock.h.
QVVideoReaderBlock::QVVideoReaderBlock | ( | QString | name = QString("") |
) |
Constructor for (virtual) QVVideoReaderBlock class.
name | the (optional) name given to the camera block. |
Definition at line 36 of file qvvideoreaderblock.cpp.
bool QVVideoReaderBlock::linkProperty | ( | QVPropertyContainer * | dstCont, | |
QString | dstProp | |||
) |
Links a QVImage<uChar,3> or QVImage<uChar,1> from the camera to another block.
This method will automatically link, using the adequate synchronism (Asynchronous for real time cameras and Synchronous for non real time cameras), a gray or an RGB image in the block to the corresponding output image property of the camera. An error (return value=false) will occur if dstProp is not of the adequate type (QVImage<uChar,3> or QVImage<uChar,1>).
dstCont | Pointer to the destination block. | |
dstProp | Name of the destination property. |
Definition at line 190 of file qvvideoreaderblock.cpp.
bool QVVideoReaderBlock::linkProperty | ( | QVPropertyContainer * | dstCont, | |
QString | dstProp1, | |||
QString | dstProp2, | |||
QString | dstProp3 | |||
) |
Links 3 QVImage<uChar,1> from the camera (YUV channels) to the corresponding ones of another block.
This method will automatically link, using the adequate synchronism (Asynchronous for real time cameras and Synchronous for non real time cameras), a set of three one channel images in the block to the corresponding output image properties of the camera. An error (return value=false) will occur if any of the dstProp are not of the adequate QVImage<uChar,1> type.
dstCont | Pointer to the destination block. | |
dstProp1 | Name of the destination property for image Y. | |
dstProp2 | Name of the destination property for image U. | |
dstProp3 | Name of the destination property for image V. |
Definition at line 207 of file qvvideoreaderblock.cpp.
virtual bool QVVideoReaderBlock::open | ( | QString | urlName, | |
int & | cols, | |||
int & | rows, | |||
int & | fps | |||
) | [protected, pure virtual] |
Pure virtual open 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). |
Implemented in QVMPlayerReaderBlock, and QVYUV4MPEG2ReaderBlock.
virtual void QVVideoReaderBlock::close | ( | ) | [protected, pure virtual] |
Pure virtual close method.
Reimplementations of this method should close the video source.
Implemented in QVMPlayerReaderBlock, and QVYUV4MPEG2ReaderBlock.
virtual bool QVVideoReaderBlock::grab | ( | QVImage< uChar, 1 > & | imgY, | |
QVImage< uChar, 1 > & | imgU, | |||
QVImage< uChar, 1 > & | imgV | |||
) | [protected, pure 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 open() 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. |
Implemented in QVMPlayerReaderBlock, and QVYUV4MPEG2ReaderBlock.
virtual double QVVideoReaderBlock::lengthOfVideo | ( | ) | [protected, pure 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)
Implemented in QVMPlayerReaderBlock, and QVYUV4MPEG2ReaderBlock.
virtual double QVVideoReaderBlock::currentPos | ( | ) | [protected, pure 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.
Implemented in QVMPlayerReaderBlock, and QVYUV4MPEG2ReaderBlock.