ks@a.cs.okstate.edu (Kurt F. Sauer) (10/29/87)
I can't find a good definition for the term "continuously variable slope delta." My (nominal) understanding is that it's a method of digitizing audio--but I'm not certain of that. Any clues? Kurt F. Sauer Tulsa, OK
larry@kitty.UUCP (Larry Lippman) (10/30/87)
In article <2767@okstate.UUCP>, ks@a.cs.okstate.edu (Kurt F. Sauer) writes: > I can't find a good definition for the term "continuously variable slope > delta." My (nominal) understanding is that it's a method of digitizing > audio--but I'm not certain of that. I'll give it a shot; it's going to be tough without graphics, though. :-) Continuously Variable Slope Delta (CVSD) Modulation is a technique for digitizing signals, usually in the audio frequency range. To understand CVSD, one must first understand delta modulation. The simplest delta modulator is 1-bit, and is in effect a 1-bit A/D converter. A fixed sample clock is extablished. The audio input signal is fed to a comparator and an integrator. At each clock interval, the input signal is compared with the integrated approximation of the _previous_ sample, and the comparator is used to determine if the input signal is more positive or more negative than the stored sample. If the signal-sample difference is positive, a binary 1 is transmitted; if the signal-sample difference is negative, a binary 0 is transmitted. In the absence of a signal, a continuous stream of alternating 0's and 1's is transmitted. In simple terms, an integrator circuit is all that is required to convert the delta modulation bit stream back to an analog signal Even though the simplest delta modulator is 1-bit, a decent signal can be digitized and reconstructed if a high enough sampling rate is used. Delta modulation represents one of the simplest methods of audio signal digitizing, and has the advantage that its serial bit stream is frameless. CVSD consists of an enhanced method of delta modulation, and is built around a delta modulator. CVSD has a digitally-controlled gain loop around the sample integrator and comparator, along with a shift register and other logic, and in effect provides delta modulation with typically 3 or 4 bits of resolution. CVSD circuits generally provide a companding function to enhance dynamic range. In addition, in limited-bandwith applications for voice, the integrating filter in a CVSD circuit is augmented with a syllabic filter to improve effective frequency response. I realize the above explanation is hopelessly oversimplified, but perhaps it will suffice to answer your question. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"