Composite algorithm for screen video key frames compression

Screen video is one of the video data types, which must be compressed in real-time mode.Often it is necessary to compress screen video in background mode at that. There is a necessity infast image compression algorithms, because during video compression key frames are encodedindependently. Screen video frames are referred to discrete-tone images. As a rule algorithmswithout information loss are used to compress such images, because while compressing such imageseven a small information loss percent can result in significant visual image degradation. RLEand family of LZ algorithms can be referred to such algorithms. LZO is actively used in screenvideo compression (for example, it is used in freeware screen video recorder CamStudio). Secondversion of hybrid algorithm, which is intended for discrete-tone images compression, is introducedin this paper. First version of hybrid algorithm was developed by the author too. Secondversion of hybrid algorithm differs from previous modifications by increased speed of executionand compression rate. Composite algorithm, which is based on hybrid algorithm and use LZO onthe final stage of compression, is also introduced in this paper. This compression scheme allowsto increase compression rate of screen video frames, which are typical for Windows XP, at theaverage of 17 % as compared with the LZO family representatives with best compression rate,which are able to compress screen video in the real-time mode on the wide variety of computers(LZO_X_999 level 6). At the same time compression rate of composite algorithm andLZO_X_999 level 6 are similar for images, which contain text, diagrams and graphs.

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