A practical tool is proposed to improve the design of various vector quantizer (VQ) structures. Particular emphasis is placed on the design of entropy-constrained VQ (ECVQ), and entropy-constrained multi-stage VQ (EC-MSVQ), whose optimization is notoriously difficult. Traditional design techniques involve an indirect approach where a fixed rate quantizer is gradually modified into a variable rate VQ. We propose a direct design procedure based on selective codevector splitting. The codebooks are grown, using splitting according to a rate-distortion Lagrangian trade-off, to the desired operating point of average bit rate. Extensive simulations in image and video compression are presented and show consistent, significant improvement over standard techniques. For example, in ECVQ design for compression of video residuals, PSNR gains of about 1.0 dB were achieved.
We investigate joint source-channel coding for transmission of video over time-varying channels. We assume that the channel state is known at the receiver, but only statistical description of the time varying nature of the channel is available at the transmitter. A multimode coder is proposed to efficiently quantize the input video, and generate a quasi fixed-length bit stream of unequal importance. We vary the error protection offered to the individual bits, by matching it to both its importance, and the channel noise statistics. Based on the channel state, the decoder makes the best estimate of the source vector from the received codeword. We present a design algorithm which optimizes the overall rate- distortion performance of the system. Simulations results show that the proposed system outperforms a reference scheme where the multimode (source) codes and the channel codes were designed separately. Further, both the multimode coding schemes provide substantial gains over fixed length JSCC coding.
Conference Committee Involvement (4)
Visual Communications and Image Processing 2009
20 January 2009 | San Jose, California, United States
Visual Communications and Image Processing 2008
29 January 2008 | San Jose, California, United States
Visual Communications and Image Processing 2007
30 January 2007 | San Jose, CA, United States
Visual Communications and Image Processing 2006
17 January 2006 | San Jose, California, United States
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