# US 5,708,429 A · Method of compressing electroencephalographic signals

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,708,429 A
- Document ID: US5708429A
- Status: Granted
- Kind: A
- Application number: 08/588,683
- Filed: 1996-01-19
- Granted: 1998-01-13
- Earliest claimed: 1995-01-26
- Assignees: Istituto Trentino Di Cultura
- Inventors: Giuliano Antoniol; Paolo Tonella
- Web page: https://patentgrep.com/patent/US5708429A

## CPC

- G06T 9/004: {Predictors, e.g. intraframe, interframe coding}
- A61B 5/372: Analysis of electroencephalograms
- A61B 5/7232: {involving compression of the physiological signal, e.g. to extend the signal recording period}
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

In a method of compressing electroencephalographic signals, the signals are compressed by the encoding of the differences between values of the signal and values estimated by a predictor with the use of variable-length codes with prefixes.

## Claims

### Claim 1

A method of generating from an analog electroencephalographic signal a compressed signal for storing and/or transmitting the compressed signal, wherein said method comprises the following steps:
converting the analog electroencephalographic signal into a signal in digital format,
generating by means of an estimator predicted values of the digital signal on the basis of the past behavior of the analog signal and generating a signal indicative of the difference between predicted values and actual values of the digital signal, and
encoding said signal indicative of the distance by means of variable-length codes with prefixes to generate the compressed signal.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the estimator generates a signal indicative of a first differential of the digital signal in order to generate the signal indicative of the distance between predicted values and actual values of the digital signal.

### Claim 3 (depends on 1)

A method according to claim 1, wherein the method comprises the step of associating a conversion table with the compressed signal in the encoding stage.

### Claim 4 (depends on 3)

A method according to claim 3, wherein the conversion table associates a string of binary numerals with each symbol present in the digital signal.

### Claim 5 (depends on 3)

A method according to claim 3, wherein the conversion table is optimized on the basis of the relative frequencies of the symbols present in the entire digital signal.

### Claim 6 (depends on 3)

A method according to claim 3, wherein the average relative frequencies of the symbols are estimated on a database containing sample digital electroencephalographic signals and the conversion table is an average conversion table obtained on the basis of the average relative frequencies.

### Claim 7 (depends on 1)

A method according to claim 1, wherein the encoding stage uses a Huffman queue.

### Claim 8 (depends on 7)

A method according to claim 7, wherein the Huffman queue uses a data structure of the type with a priority code.

### Claim 9 (depends on 8)

A method according to claim 8, wherein said method comprises the steps of:
calculating a vector of the differences Y;
calculating frequencies of the symbols in Y;
inserting the symbols of Y in a priority queue H having frequency as a key;
constructing a binary tree B from said priority queue H;
traversing said tree B in pre-order thus constructing an encoding table tab; and
creating a compressed signal including therein the table tab used for encoding and an initial value of the signal.

### Claim 10 (depends on 7)

A method of decompressing a signal compressed by a compression method according to claim 7, wherein the compression method comprises the steps of:
reconstructing said binary tree B from said encoding table tab;
decoding strings of bits input by traversing said binary tree B; and
reconstructing the compressed signal from symbols Y.

### Claim 11 (depends on 6)

A method according to claim 6 wherein, said method comprises the steps of:
associating with said compressed signal said initial value of said electroencephalographic signal in digital format; and
calculating the difference y and encoding the calculated difference Y.

### Claim 12 (depends on 11)

A method of decompressing a signal compressed by the compression method according to claim 11, wherein the decompression method comprises the steps of:
constructing a binary tree from the encoding table tab;
acquiring an initial value of said electrocephalographic signal; and
decoding strings of bits input by traversing said binary tree B.