Design of Robust VLC Codecs Motivation Variable Length

Design of Robust VLC Codecs • Motivation – Variable Length Codes (VLC) are known to give efficient compression – VLC are also vulnerable in noisy environments because of synchronization losses that comes from bit errors symbol VLC Coder Channel Bit error Data packet Lost data VLC Decoder symbol

“Alternative” VLC Code • Standardized error-resilient coding (MPEG-4) – Reversible codes (can be decoded from both ends) – Does not provided true error-resilience (relies on side information in the data) – “High” computational complexity • “Alternative” VLC code – Coder and decoder simplified – Enables high-speed decoding – Provides error-resilience to the price of less efficiency – Single bit errors results in less severe errors

“Alternative” VLC Code • Current status – HW implementation started – expected to be completed in September 2002 • Expected results – Comparison to state-of-the art decoder • HW complexity • Decoding speed • Power consumption

Hybrid Golumb (HG) Codes • Motivation – Compressed video data are very well modeled by “Generalized Gaussian Disribution” Source paramters , , • Existing VLC codes are sensitive to variations in the source parameters • Coding efficiency may be lower than 20%

Hybrid Golumb (HG) Codes • Our codes (HG) • Always >70% for a wide range of parameter values • Always higher efficiency under parameter scaling • Not best for certain parameter values – Golomb-Rice (GR) and exp-Golomb (EG) codes performs optimal or near-optimal for small range of values

Robust Window Discriminator for Photon Counting Pixel Detectors • Goal – Develop circuit design techniques for low-noise / low-power / area-efficient digital functions

Robust window discrimination • Event-driven window discrimination – – – Does not rely on internal or external timing references To be used over a wide range of specifications All-digital solution (ADWD) Area-efficient Constraints on the design of the integral discriminators – built-in hysteresis Reported in: Bengt Oelmann, Munir Abdalla, and Mattias O'Nils, "Robust Window Discriminator for Photon Counting Pixel Detectors ", IEE Optoelectronics, 2002.

On-going design work • Goal: – Design and fabricate photon-counting pixel – Characterize pixels that are based on the design techniques that we propose Shift_clk Low_th ADWD PRESCALE 7 bit MUX LFSR 10 bit Read_out High_th Enable_count Read_in Prescale-LFSR configuration Mattias O’Nils, Munir Abdalla, and Bengt Oelmann, "Low Digital Interference Counter for Photon Counting Pixel Detectors ", to appear in Nuclear Instrumentation and Mehods 2002.

Low-power Finite-State Machine Design • Goal: – Develop optimization procedures and implementation architectures for low-power FSM • Current status – “Extensive pre-study” completed • • Design model its formal description Procedures for “state bundling” and state encoding HW Implementation architecture Partitioning procedures

Future work on FSMs • Demonstrators – Implement the optimization procedures in a CAD-tool – Use the CAD-tool in different application areas CAD-tool LIFS 2 Microprocessor Design Data Communication Digital Signal Processing