Accession Number : ADD013356
Title : Secure Digital Speech Communication.
Descriptive Note : Patent, Filed 26 Jun 84, patented 14 Jul 87,
Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON DC
Personal Author(s) : Benke, George
Report Date : 14 Jul 1987
Pagination or Media Count : 32
Abstract : A novel form of waveform coding is used, designated a Critical Point Coder (CPC). It operates by transmitting only those points in a waveform which are significant for defining its overall structure. The receiver reconstructs the missing points in the waveform using some sort of approximating interpolation. The critical Point Coder uses a new approach to waveform coding. Rather than transmitting information about each sample as other waveform coders, the Critical Point Coder transmits information for only samples deemed critical to high quality reconstruction. The four major functions performed by the Critical Point Coder are (1) detecting which samples are critical, called critical points e.g. those points in the waveform where it is changing direction most rapidly, generally the peaks and valleys; (2) quantizing the vectors which are formed between successive critical points; (3) dealing with the non-uniform bit rate since critical points do not occur regularly; and (4) reconstructing the waveform between the endpoints of the quantized vectors. For stabilizing the bit rate, stabilization intervals of fixed duration are divided into equal analysis intervals, with logic to select from three modes for quantizing and encoding the vectors during each stabilization interval, depending upon the stepsize.
Descriptors : *CODERS, *DIGITAL COMMUNICATIONS, *PATENTS, *VOICE COMMUNICATIONS, CODING, DIGITAL SYSTEMS, INTERPOLATION, INTERVALS, SAMPLING, SECURITY, SPEECH, TIME, TRANSMITTING, VALLEYS, WAVEFORMS, WAVE ANALYZERS, SECURE COMMUNICATIONS, SIGNAL PROCESSING
Subject Categories : Command, Control and Communications Systems
Distribution Statement : APPROVED FOR PUBLIC RELEASE