question: 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 . concode_field_sep long nativeObj concode_field_sep boolean n_isOpened concode_elem_sep boolean n_read concode_elem_sep boolean isOpened concode_elem_sep boolean set concode_elem_sep void release concode_elem_sep boolean n_set concode_elem_sep void n_delete concode_elem_sep void n_release concode_elem_sep List<Size> getSupportedPreviewSizes concode_elem_sep String n_getSupportedPreviewSizes concode_elem_sep boolean n_retrieve concode_elem_sep boolean n_retrieve concode_elem_sep double get concode_elem_sep boolean n_open concode_elem_sep boolean n_open concode_elem_sep boolean retrieve concode_elem_sep boolean retrieve concode_elem_sep void finalize concode_elem_sep boolean grab concode_elem_sep long n_VideoCapture concode_elem_sep long n_VideoCapture concode_elem_sep long n_VideoCapture concode_elem_sep boolean n_grab concode_elem_sep boolean open concode_elem_sep double n_get
target: boolean function ( Mat arg0 ) { boolean loc0 = n_read ( nativeObj , arg0 . nativeObj ) ; return loc0 ; }