If no frames has been grabbed (there are no more frames in video file), the methods return ``false`` . The method throws :ocv:class:`Exception` if error occurs.
:param source: Video file parser implemented by user.
The constructors initialize video reader. FFMPEG is used to read videos. User can implement own demultiplexing with :ocv:class:`gpu::VideoReader_GPU::VideoSource` .
The method opens video reader. Parameters are the same as in the constructor :ocv:func:`gpu::VideoReader_GPU::VideoReader_GPU` . The method throws :ocv:class:`Exception` if error occurs.
gpu::VideoReader_GPU::isOpened
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Returns true if video reader has been successfully initialized.
If no frames has been grabbed (there are no more frames in video file), the methods return ``false`` . The method throws :ocv:class:`Exception` if error occurs.