| The techniques keep developing in VLSI, multimedia data compression, high-bandwidth networks and large-capacity storage device. Thanks to those developments, limitations come from system architecture and data compression and transmission and storage have been broken in video application field. Under this circumstance, the video have been widely used in entertainment, media, security surveillance and digital recording and other fields.Video has the characteristics of playing in real-time, that means playing frame interval must be greater than one visual reaction time in order to ensure continuity. And the requirement of displaying video is the refreshing rate must be greater than the distinguish frame rate of the human eyes. So the sense and feeling of user is different from the traditional showing of texts and static pictures, which brings challenges to the traditional graphical user interface which is compose of text and image, namely how to make video oriented applications have more friendly man-machine interface.In order to solve this contradiction, OSD (On Screen Display, OSD) is presented, which is a way of mixing the user interface with the video on the overlay. OSD is usually implemented in hardware, providing small resolution of small number of low-color text and graphics display interface, and has been widely used in embedded systems. In the desktop computer, the lack of relevant hardware, a compromise approach is to separate the GUI display from video display, but the trade-offs failed when display in full-screen. In order to resolve the issue of Failure, the design and implementation of software OSD is presented. Further more, GUI is transplanted to this OSD, which is constructed to realize video GUI. The research of video GUI that used to improve the interactive nature of video applications is of great significance.During the GUI design and realization, a method of communication between objects based on signal - slot mechanism is presented this paper, which enable objects to process messages. What's more, the message-driven model and object model of GUI are built on this fundamental mechanism. The way of combination of compiling-time and running-time is used to realize signal - slot mechanism, which reduces both reliance on pre-processing tools and ensures efficiency. On this basis, this paper realizes the common control library of the user interface design, and API interfaces are provided to the design of video applications.Compared with the normal GUI, video GUI's hierarchical structure of data flow is more obvious. And the flow is divided into application layer, data layer, OSD layer and the abstraction layer, and theory of each level that involved are analysis in depth. Among those four layers, data layer involves issues of mapping OSD regional mixture, in order to minimize the number that OSD builder has to compute, the measure of tow level mapping GUI area to OSD blending area is proposed; and a method, called Parallel Computing Delayed Quote, is used in processing GUI graphics and video frame, which ensures the real-time of video playback; OSD builder provides two kind of alpha mixing method, the first mixture happens between GUI graphics display result and pixels of widget, another is blending GUI graphics display result and video frame, this tow kind of way could blend GUI foreground and background videos at any point with the an arbitrary value of Alpha, and the result frame looks more natural and intuitive; video as OSD mixer to another input, in order to enable the mixer is compatible with a variety of video sources, this paper designed a reusable video processing framework that defines the access to data interface, so that video GUI can be easily applied in different occasions.Finally, an instance of television playing terminal on treadmill is designed by using video GUI. This video oriented application on Linux shows that user interface build on APIs of this video GUI are user-friendly and with good interactivity. |
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