VLSI design of a programmable DCT engine for digital cameras

In still image compression, the JPEG lossy still image compression standard for continuous tone image is often used. JPEG compression efficiency is achieved by decorrelating an image using Discrete Cosine Transform (DCT). Resulting quantized DCT coefficients are then entropy coded for higher compression efficiency. In the quest for higher compression efficiency, wavelet is an attractive alternative at the cost of higher computational complexity. It is proposed in here that DCT followed by Embedded Zerotree Coding (EZC) of DCT coefficients can be competitive to wavelet compression scheme. The basis of competitiveness is based on achievable visual quality at medium bit rate relevant to digital camera applications. As the computational complexity of proposed compression scheme using DCT followed by EZC is still dominated by DCT operations, it is also proposed in here that a very efficient DCT algorithm should be used that has a good computational complexity as well as good inherent parallelism. Finally, a VLSI design is proposed in here that harnesses the inherent parallelism in the efficient DCT algorithm for digital camera applications.