TARGET_FRAME
A long indicating the time position (in microseconds) of the target frame which will be retrieved. getFrameAtTime is used to extract the video frame.
When retrieving the frame at the given time position, there is no guarantee that the data source has a frame located at the position. When this happens, a frame nearby will be returned. If the long is negative, time position and option will ignored, and any frame that the implementation considers as representative may be returned.