Design And Implementation Of The Image Evaluation And Test Software In Digital Video Recorder

DVR is a multi-functional and highly adaptable device than can do things much more than video recording and playback. With its different types of communication interfaces provided as well as modularized software design, digital hard disk recorders are capable of functioning adaptably to different industries even with different monitoring specification requirements. Therefore, specialization is an important developing direction of DVR, and we have seen products specifically designed for ATM monitoring, self-help bank monitoring, in-vehicle monitoring and trial monitoring.Playback is an important feature of DVR. How to improve the resolution of video is a crucial development to DVR. The quality of the video could be improved by either strengthening resolution or reducing loss during compression. At present the highest resolution employed by DVR is 720*576, and most frequently used compressing resolution 352*288 or 704*576 with H.264 the most popular compression algorithm. Often on TV programs there shows criminals'actions recorded by the surveillance devices, however, because of the trade-off between DVR storage space and resolution of the video, in practice the resolution is usually sacrificed for larger storage space as a result of which characteristics shown in the screen are too vain to be accurately captured. The solution to this problem will be more advanced video compression algorithm.But how to evaluate these video compression algorithm? One way of doing it would be observing the image with naked eye to see if there is color distortion, mosaic, unclear image edges or poor brightness. But these are all based on the feeling of the observers, and different people could have different judgments. In this work, with reference to the standard algorithm the comparison between video images before and after digital compression was made with the lost part due to the compression process extracted and processed, the author has come to an objective value---signal-noise ratio, which can be used in evaluation of the compression process.In this work the DVR video compression coding methods was analyzed, and with the basis of the working principle of video compression algorithm a method of calculating the "frame rate," "Resolution" and "SNR" was discussed in details. The program source code was written, with program tested. The work mainly includes the following several areas: 1. Analysis on the video decoding method of DVR, 2. Provision of reference video source for testing purpose, 3. Details of playback video capturing on DVR, 4.Detailed description of the testing process of "frame rate", "resolution" and "SNR", 5. Evaluation of the testing process and results after running the software.