Delta modulation method and system for signal compression

• US 4,314,105 A
• Filed: 10/02/1979
• Issued: 02/02/1982
• Est. Priority Date: 01/21/1977
• Status: Expired due to Term

• Current Assignee: Electronic Speech Systems, ESS Technology Incorporated (Semiconductor Holding Corp.)
• Original Assignee: Forrest S. Mozer
• Inventors: Mozer, Forrest S.
• Primary Examiner(s): Nusbaum, Mark E.
• Assistant Examiner(s): Kemeny, E. S.
• Application Number:
  US06/081,281
• Time in Patent Office: 854 Days
• Field of Search: 179/15.55 R, 179/1 SM, 179/1 SA, 332/11 D, 375/27, 375/28, 358/260, 358/261, 340/347 DD
• US Class Current: 375/246
• CPC Class Codes: G10L 13/047 Architecture of speech synthesisers
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: H04B 14/062 using delta modulation or one-bit differential modulation [1DPCM]

Abstract

This delta modulation system uses the differences between three successive samples of a waveform (the i-1, i, and i+1) such that the number of bits per digitization is reduced from four to two. The value vi of the ith sample is calculated by the equation v_i =v_i -1+f(Δ_i-1, Δ_i), and f is a special function defined by 16 values stored in a read-only memory.

Claims

1. A system for expanding floating zero delta modulated compressed information signals corresponding to original information time domain signals, said system comprising:

memory means for storing said compressed information signals;

storage means for temporarily storing a signal representative of the amplitude of a sample point on a synthesized waveform corresponding to one of said original information time domain signals, said storage means having an output terminal for manifesting the signals stored therein;

means for contemporaneously accessing successive compressed information signals corresponding to three adjacent sample points of said original information signals;

means coupled to said accessing means for comparing said successive compressed information signals accessed from said memory means and for generating an incremental signal value restricted to one of a predetermined confined number of values when the difference between said successive compressed information signals is within the most positive one half of said confined number of values and restricted to the negative of said one of a predetermined confined number of values when said difference is within the most negative one half of said confined number of values;

adder means coupled to said generating means and said storage means for algebraically combining said incremental signal value with said synthetic waveform sample point signal to produce a successive synthesized waveform sample point signal; and

timing and control means for replacing the contents of said storage means with said successive synthesized waveform sample point signal and for enabling said accessing means to contemporaneously access the next successive compressed information signals corresponding to the next adjacent sample points.

2. The combination of claim 1 wherein said memory means and said storage means are digital storage devices, and wherein said compressed information signals and said synthetic waveform sample point signals are digital characters.

3. The combination of claim 1 wherein said generating means includes a memory device for storing signals corresponding to a complete set of said confined number of values, and address means for reading said incremental signal value in response to the application of said successive compressed information signals thereto.

4. The combination of claim 3 wherein said memory device comprises a read-only memory.

5. The combination of claim 1 wherein said accessing means includes a temporary storage register for storing said successive compressed information signals.

6. The combination of claim 1 wherein said timing and control means includes means for supplying an initial preselected value of said synthesized waveform sample point signal to said storage means and means for supplying an initial preselected value of one of said successive compressed information signals to said generating means at the beginning of a cycle of operation.

7. The combination of claim 1 wherein said system further includes means coupled to said storage means output terminal for combining successive synthesized waveform sample point signals to produce said synthesized waveform.

8. The combination of claim 7 wherein said successive synthesized waveform sample point signals are digital characters, and wherein said combining means includes a digital to analog converter.