Digital Data Communication
An effective and efficient
communication mechanism is necessary in an environment where image
data and control signals must be disseminated in real-time or in off-line
fashion for visualization, off-site analysis, and distance control.
Key technologies toward this end include computer network protocols,
image compensation, image/signal scalable compression (lossless/lossy
compression for different research purposes, scalable browsing), and
pre- and post-image processing (de-noising, enhancement, etc.).
For control signals, reliability
is important; for astronomical images, scalable delivery should be
supported to meet the requirements of different applications. In this
activity, a prioritized transmission scheme is employed. For example,
areas of interest (AOI) in the images will be assigned higher priority
and a higher level of protection during transmission.
Compression is another important
component of this activity. Due to the large volume of astronomical
images, compression technology is essential to reduce communication
cost as well as to achieve more efficient storage. Wavelet-based compression
attracts a lot of attention due to its superior performance in texture
compression, e.g. there is no block effect. In addition, the multi-resolution
nature of wavelet transform supports scalable compression very well,
which is a highly desirable feature for layered streaming, scalable
browsing, among others. In this research, a real-time content-based
wavelet image codec is designed to achieve time and space efficiency.
For the continuous image sequence obtained by the telescope, 3-D wavelet
compression is employed to increase the compression ratio. The quality
of reconstructed images can be improved by pre- and post-processing
them to remove possible noise and artifacts.