Universal Tuner streams video to various hand-held or mobile phone devices through wireless connectivity. In this project, we implemented a prototype of a variable-complexity codec that can transcode MPEG-1/2 video or live TV broadcasting in real-time and stream it to the Palm-OS Personal Digital Assistant (PDA) devices. Figure 1 shows the system architecture of Universal Tuner. Due to the limited processing capability, memory constraints, and the power budget of mobile clients, multimedia coders and/or decoders are often difficult to implement on wireless handheld PDAs.

In this Universal Tuner project, we designed and implemented a wireless video streaming system that transcodes MPEG-1/2 videos or live TV broadcasting videos to the BW or indexed color Palm OS devices. In our system, the complexity of multimedia compression and decompression algorithms is adaptively partitioned between the encoder and decoder. A mobile client would selectively disable or reenable stages of the algorithm to adapt to the device’s effective processing capability. Our variable-complexity strategy of selective disabling of modules supports graceful degradation of the complexity of multimedia coding and decoding into a mobile client’s low-power mode, i.e. the clock frequency of its next-generation low power CPU has been scaled down to conserve power. We modified the structure of the standard motion-compensated DCT video codecs to implement a simplified the encoder on a PC server and the decoder on a complexity-constrained PDA viewing client.

Figure 1: System Architecture of Universal Tuner

Figure 2:  Stages in a partitioned compression (encoder) and decompression (decoder) algorithmic pair are selectively disabled and reenabled to vary the complexity.

Figure 3:  Application Modes of Universal Tuner: (a) video is shown in the 80x80 mode with other functionalities; (b) video is shown in the full screen (160x160) mode.