Synchronization of analog video signals with improved image stability

摘要

Sync digital multimedia devices today feature analog composite or S-video inputs for compatibility reasons. We expect that interface to be included for the medium term future, since analog VCRs still make up a significant part of today's purchased home recording devices. Nowadays, sync processing is done mainly digital, however based on the traditional techniques of sync slicing and smoothing using a PLL (phase-locked loop). Due to its recursive nature, the PLL is limited to a second order loop, which limits its filter performance. Limited filter performance results in the well known picture stability compromise, where noise suppression has to be compromised with VCR-playback picture stability. We introduced a concept which replaces the PLL by non-recursive processing. Removing the stability issues of recursive processing opens a large parameter range for filter design and optimization. In this paper, we give a discussion of the parameter optimization effects and results, which includes subjective quality tests. The research was greatly supported by a real-time implementation of the novel algorithm using an industry standard FPGA.