Browsing by Author "Bharadwaj, Vinay"

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    A DSP-Based Platform for Wireless Video Compression
    (2002-11-01) Murphy, Patrick; Bharadwaj, Vinay; Welsh, Erik; Frantz, Patrick; Center for Multimedia Communications (http://cmc.rice.edu/)
    With the exponential growth of wireless voice markets, demand for wireless video services is soon to follow. However, bandwidth limited wireless channels coupled with mobility issues pose a great challenge in the hardware, software and algorithm design of communication systems. Raw video transmission is a high bandwidth application due to its spatial and temporal redundancies. Hence effective video communication over wireless channels calls for intelligent video coding and protection schemes. Also, the real-time nature of video necessitates high performance hardware and efficient software. This paper describes a modular and standards-independent DSP-based testbed (Paladin) designed for real-time video communication over low-bandwidth channels. In particular, we demonstrate the real-time transmission of MPEG-4 video and JPEG2000 still images over the Bluetooth wireless standard. Such a demonstration has many potential applications. We have designed the testbed to explore the possibilities, demands, and challenges of real-time wireless video transmission. We have implemented the MPEG-4 and JPEG2000 source coding on two DSP platforms: a Texas Instruments (TI) TMS320C6211, and a TI TMS3206416.
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    Joint Source Channel Coding for Discrete Memoryless Channels
    (2000-05-20) Bharadwaj, Vinay; Center for Multimedia Communications (http://cmc.rice.edu/)
    The design of optimal joint source/channel coding and decoding is examined for dis­ crete memoryless channels with end­to­end distortion as the criterion for reliable com­ munication. Joint source/channel encoders which map sequences of source symbols directly to sequences of channel symbols without any intermediate "bit" representa­ tion of source are considered. Optimum joint source/channel decoder that minimizes end­to­end distortion for a given encoder mapping is derived. The encoder mapping can be many to one, in the sense that many source sequences can be mapped to one sequence of channel symbols. To begin with, as an exercise, random coding bound on end­to­end distortion is derived for a general Maximum A Posteriori (MAP) decoder which has some estimate on the apriori probabilities of source symbols. It is shown that, the KL distance of the actual apriori probabilities with the estimated ones plays an important role. Then, a random coding bound on end­to­end distortion is derived with our optimal minimum distortion decoder mentioned above for the case when all source symbols are equally likely. It is shown that the performance increase with min­ imum distortion decoding as opposed to MAP (same as Maximum Likelihood (ML) decoding in this case when all source symbols are equally likely) is characterized by the faster decay of end­to­end distortion with respect to channel use.