Real-Time Decompression of Streaming Video Using Mobile Code

Abstract

In [1, 2] w eproposed novel multimedia compression schemes, called 2D-PMC, based on approximate pattern matching. These schemes are lossy extensions of the w ell-known Lempel-Ziv schemes. The central theme of a lossy extension of the Lempel-Ziv algorithm is the notion of approximate repetitiveness. A highly desirable feature of our schemes is that the associated decompressors are extremely fast and simple. This enables their implementation in mobile code that can be shipped along with the media with little communication overhead. F urthermore, ev en on relatively outdated platforms (P entium II/350, 128MB, Windows NT4.0), our mobile code ac hieves real time performance at 25 frames/second on frames of size 360 288. We report here, some preliminary experimental results from the MobilVideo decoder. These results indicate that the associated decoder is an order of magnitude faster than an MPEG2 decoder and faster than other streaming video decoders such as VivoActive, RealSystem G2, and jStreaming in native form (machine code). The MobilVideo decompressor for 2D-PMC is fashioned as a Java applet that communicates the image or video segment, decompresses it, and renders it. These three main tasks are implemented as highly optimized threads to maximize concurrency. Compressed data is copied into the input bu er in (programmable) ch unks of size 2KB by the reader thread. The size of this ch unk is selected to optimize netw ork latency, bu er management overheads, and compressed image sizes. This data is decompressed by the decompressor thread and resulting frames are copied into the display bu er one frame at a time. These are then displayed b y the render thread. The compression ratios, and compression and decompression times for 2D-PMC are as follows: