MDNAP is a comprehensive CAD tool for discrete-domain 1, 2 or 3-dimensional filters and in a limited capacity for continuous-domain filters. Based on the Signal-Flow Graph (SFG) description of the filter, MDNAP is capable of performing frequency-domain and sensitivity analysis for both discrete-domain and continuous-domain filters and spatiotemporal-domain analysis for discrete-domain filters. In addition to a SFG description of the filter, MDNAP offers a means for incorporating fixed-point precision of filter coefficients and node variables.
Spatiotemporal-domain Analysis of discrete-domain filters:
Linear-Trajectory Filter Example:
Linear-trajectory (LT) 3-D filters are capable of being tuned to pass objects moving at a particular velocity in a video sequence. Here is an example of using MDNAP to examine quantization effects in a particular implementation of a LT filter.
One of the critical parameters in filter hardware implementations is data wordlength, which determines the precision and dynamic range of the signals. Choosing a too-short data wordlength can result in filter instability; choosing a too-long data wordlength makes the hardware too expensive.
The input sequence (256x240, 53 frames, MPEG, 499k) was filmed at a local brewery. Note that it contains several objects moving with different velocities.
A filter structure capable of implementing a LT filter was designed, and the coefficients were tuned to pass the diagonally-moving beer cases. In order to investigate the effects of changing wordlength, a simulation (256x240, 53 frames, MPEG, 120k) of a 16-bit hardware implementation of this filter was performed, and the filter was found to perform very well. However, a simulation (256x240, 11 frames, MPEG, 44k) of an 8-bit implementation showed that filter becomes unstable.
See this paper for more details.
MDNAP source is written in C and, to date, has been compiled for SUN SPARCstations, NeXTstations and DOS-based Intel 386-and-up machines. MDNAP is not public software. If you are interested, contact me or Dr. L.T. Bruton.
University of Calgary M-D DSP Group Home Page