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OpenCV 2.4.3.1
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## org.opencv.highgui
Class VideoCapture

    java.lang.Object
      org.opencv.highgui.VideoCapture

    public class VideoCapture

extends java.lang.Object

Class for video capturing from video files or cameras. The class provides C++ API for capturing video from cameras or for reading video files. Here is how the class can be used:

#include "opencv2/opencv.hpp" ``

// C++ code:

using namespace cv;

int main(int, char)

VideoCapture cap(0); // open the default camera

if(!cap.isOpened()) // check if we succeeded

return -1;

Mat edges;

namedWindow("edges",1);

for(;;)

Mat frame;

cap >> frame; // get a new frame from camera

cvtColor(frame, edges, CV_BGR2GRAY);

GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);

Canny(edges, edges, 0, 30, 3);

imshow("edges", edges);

if(waitKey(30) >= 0) break;

// the camera will be deinitialized automatically in VideoCapture destructor

return 0;

Note: In C API the black-box structure `CvCapture` is used instead of `VideoCapture`.

See Also:
  org.opencv.highgui.VideoCapture

Field Summary
`protected long` | `nativeObj`

Constructor Summary
`` | `VideoCapture()` VideoCapture constructors.
`` | `VideoCapture(int device)` VideoCapture constructors.
`protected` | `VideoCapture(long addr)`

Method Summary
`protected void` | `finalize()`
`double` | `get(int propId)` Returns the specified "VideoCapture" property.
`java.util.List<Size>` | `getSupportedPreviewSizes()`
`boolean` | `grab()` Grabs the next frame from video file or capturing device.
`boolean` | `isOpened()` Returns true if video capturing has been initialized already.
`boolean` | `open(int device)` Open video file or a capturing device for video capturing The methods first call "VideoCapture.release" to close the already opened file or camera.
`boolean` | `read(Mat image)` Grabs, decodes and returns the next video frame.
`void` | `release()` Closes video file or capturing device.
`boolean` | `retrieve(Mat image)` Decodes and returns the grabbed video frame.
`boolean` | `retrieve(Mat image, int channel)` Decodes and returns the grabbed video frame.
`boolean` | `set(int propId, double value)` Sets a property in the "VideoCapture".

Methods inherited from class java.lang.Object
`clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### nativeObj

    protected final long nativeObj

Constructor Detail

### VideoCapture

    public VideoCapture()

  VideoCapture constructors.

  Note: In C API, when you finished working with video, release `CvCapture` structure with `cvReleaseCapture()`, or use `Ptr` that calls `cvReleaseCapture()` automatically in the destructor.

  See Also:
    org.opencv.highgui.VideoCapture.VideoCapture

### VideoCapture

    public VideoCapture(int device)

  VideoCapture constructors.

  Note: In C API, when you finished working with video, release `CvCapture` structure with `cvReleaseCapture()`, or use `Ptr` that calls `cvReleaseCapture()` automatically in the destructor.

  Parameters:
    `device` - id of the opened video capturing device (i.e. a camera index). If there is a single camera connected, just pass 0.
  See Also:
    org.opencv.highgui.VideoCapture.VideoCapture

### VideoCapture

    protected VideoCapture(long addr)

Method Detail

### finalize

    protected void finalize()
                     throws java.lang.Throwable

  Overrides:
    `finalize` in class `java.lang.Object`
  Throws:
    `java.lang.Throwable`

### get

    public double get(int propId)

  Returns the specified "VideoCapture" property. Note: When querying a property that is not supported by the backend used by the "VideoCapture" class, value 0 is returned.

  Parameters:
    `propId` - property identifier; it can be one of the following: * CV_CAP_PROP_FRAME_WIDTH width of the frames in the video stream. * CV_CAP_PROP_FRAME_HEIGHT height of the frames in the video stream.
  See Also:
    org.opencv.highgui.VideoCapture.get

### getSupportedPreviewSizes

    public java.util.List<Size> getSupportedPreviewSizes()

### grab

    public boolean grab()

  Grabs the next frame from video file or capturing device.

  The methods/functions grab the next frame from video file or camera and return true (non-zero) in the case of success.

  The primary use of the function is in multi-camera environments, especially when the cameras do not have hardware synchronization. That is, you call `VideoCapture.grab()` for each camera and after that call the slower method `VideoCapture.retrieve()` to decode and get frame from each camera. This way the overhead on demosaicing or motion jpeg decompression etc. is eliminated and the retrieved frames from different cameras will be closer in time.

  Also, when a connected camera is multi-head (for example, a stereo camera or a Kinect device), the correct way of retrieving data from it is to call "VideoCapture.grab" first and then call "VideoCapture.retrieve" one or more times with different values of the `channel` parameter. See http://code.opencv.org/projects/opencv/repository/revisions/master/entry/samples/cpp/kinect_maps.cpp

  See Also:
    org.opencv.highgui.VideoCapture.grab

### isOpened

    public boolean isOpened()

  Returns true if video capturing has been initialized already.

  If the previous call to `VideoCapture` constructor or `VideoCapture.open` succeeded, the method returns true.

  See Also:
    org.opencv.highgui.VideoCapture.isOpened

### open

    public boolean open(int device)

  Open video file or a capturing device for video capturing

  The methods first call "VideoCapture.release" to close the already opened file or camera.

  Parameters:
    `device` - id of the opened video capturing device (i.e. a camera index).
  See Also:
    org.opencv.highgui.VideoCapture.open

### read

    public boolean read(Mat image)

  Grabs, decodes and returns the next video frame.

  The methods/functions combine "VideoCapture.grab" and "VideoCapture.retrieve" in one call. This is the most convenient method for reading video files or capturing data from decode and return the just grabbed frame. If no frames has been grabbed (camera has been disconnected, or there are no more frames in video file), the methods return false and the functions return NULL pointer.

  Note: OpenCV 1.x functions `cvRetrieveFrame` and `cv.RetrieveFrame` return image stored inside the video capturing structure. It is not allowed to modify or release the image! You can copy the frame using "cvCloneImage" and then do whatever you want with the copy.

  Parameters:
    `image` - a image
  See Also:
    org.opencv.highgui.VideoCapture.read

### release

    public void release()

  Closes video file or capturing device.

  The methods are automatically called by subsequent "VideoCapture.open" and by `VideoCapture` destructor.

  The C function also deallocates memory and clears `*capture` pointer.

  See Also:
    org.opencv.highgui.VideoCapture.release

### retrieve

    public boolean retrieve(Mat image)

  Decodes and returns the grabbed video frame.

  The methods/functions decode and return the just grabbed frame. If no frames has been grabbed (camera has been disconnected, or there are no more frames in video file), the methods return false and the functions return NULL pointer.

  Note: OpenCV 1.x functions `cvRetrieveFrame` and `cv.RetrieveFrame` return image stored inside the video capturing structure. It is not allowed to modify or release the image! You can copy the frame using "cvCloneImage" and then do whatever you want with the copy.

  Parameters:
    `image` - a image
  See Also:
    org.opencv.highgui.VideoCapture.retrieve

### retrieve

    public boolean retrieve(Mat image,
                            int channel)

  Decodes and returns the grabbed video frame.

  The methods/functions decode and return the just grabbed frame. If no frames has been grabbed (camera has been disconnected, or there are no more frames in video file), the methods return false and the functions return NULL pointer.

  Note: OpenCV 1.x functions `cvRetrieveFrame` and `cv.RetrieveFrame` return image stored inside the video capturing structure. It is not allowed to modify or release the image! You can copy the frame using "cvCloneImage" and then do whatever you want with the copy.

  Parameters:
    `image` - a image
    `channel` - a channel
  See Also:
    org.opencv.highgui.VideoCapture.retrieve

### set

    public boolean set(int propId,
                       double value)

  Sets a property in the "VideoCapture".

  Parameters:
    `propId` - property identifier; it can be one of the following: * CV_CAP_PROP_FRAME_WIDTH width of the frames in the video stream. * CV_CAP_PROP_FRAME_HEIGHT height of the frames in the video stream.
    `value` - value of the property.
  See Also:
    org.opencv.highgui.VideoCapture.set

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