JPS58223927A - Data compression processor - Google Patents

Abstract

PURPOSE:To compress data continuously with high compression rate and good reproducibility, by representing an input signal comprising a data showing a prescribed time series and a data showing the difference of the amplitude at adjacent time from a secondary differentiating filtering processing output. CONSTITUTION:A signal applied to a secondary differentiating filter 1 is discriminated for whether it is a peak or a zero cross significatnt signal. The peak and the zero crossing point of a filtering output section are recognized at a peak detector 3 and a zero cross point detector 4 and the time is detected. The amplitude of the original signal at the detected time is obtained at a reference device 5. Then, the amplitude of the time series signal just before being an output signal of a delay device 6 and the amplitude of the signal at present are subtracted at a subtractor 7 and the difference of the amplitude values is obtained. As to the original signal where the ratio exceeds a prescribed threshold value at a voltage-time comparator 8, it is subtracted separately from the output of the device 6, allowing to reproduce the original signal with fidelity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to data compression of signals, and more particularly to a data compression processing device for biological signals.

When automatically measuring biological signals such as electrocardiogram signals, it is necessary to accumulate A/D-converted time-series biological signals over a certain period of time and then apply processing to the accumulated time-series signals. The value 1 is measured by t, such as time. here,
The amount of data of the digitized signal to be accumulated is (A/
D converter sampling frequency) x (data acquisition time)
X (number of simultaneously acquired channels), and generally the amount of data is large, so a large capacity memory or external auxiliary storage device is required to store this data as it is.

Therefore, several data compression methods have been attempted in order to simplify and downsize the device in practical use. As a typical example, a time-series signal within a set amplitude value range within a set time is represented by the average amplitude value and time of the maximum amplitude value and minimum amplitude value of the signal group within that time,
For a signal that shows a sharp change exceeding a certain amplitude range, there is a method of data compression by representing the change in amplitude value and the time of change, or an encoding function determined by time-amplitude value. Examples include a band compression method using a variable sample density encoding method, which leaves the amplitude value at the intersection with the time-series signal as compressed data.

However, the former cannot necessarily reproduce the original signal faithfully because the reproduced waveform is expressed by a straight line with a slope of a certain time width and a horizontal straight line, and the latter has the disadvantage that it is difficult to reproduce the original signal faithfully. It had the disadvantage of requiring a processor.

On the other hand, if the original signal is a periodic signal, there is also a method of data compression using measurement values related to the basic waveform by repeating the basic preparation group.For example, as in electrocardiogram measurement, the waveform measurement part is This method saves the measured values only for heartbeats.However, continuous data compression is required for signals that are not necessarily periodic, such as biological signals, such as electrocardiograms that show arrhythmia phenomena.

The purpose of the present invention is to provide a data compression processing device that can perform continuous data compression with a simple method, high speed processing, high compression rate, and good reproducibility, compared to conventional data compression methods. The goal is to provide the following.

According to the present invention, there is provided a means for applying a second-order differential filtering process to a signal to be processed, and an output signal obtained by second-order differentiating the occurrence time of a signal to be selected from among the time-series signals of the liquid concentrate constituting the signal to be processed. means for comparing the amplitude value of the original signal at the occurrence time of the current selection target secondary differential signal with the amplitude value of the original signal at the occurrence time of the immediately previous selection target secondary differential signal; A data compression processing device is obtained, which includes means for synthesizing the time interval and the difference value of the amplitude values of the two original signals to generate compressed data of the signal to be processed.

First, a formula for second-order differential filtering that applies a second-order differential operation to a signal to be processed is shown in equation (1).

Xk+□+Xk-□) 10-(xk+2 + Xk-x) + 0・(Xk+s+
Xk-s) + 1・(Xk+4+Xk-4)+2@(Xk+s+Xk-4)+1・(Xk+s+xk-s)'j...Formula (1) where (X
k) is each sampled time series monitor shown in FIG. 1, for example. Also, η窀■ding indicates a scale factor. As shown in equation (1), the coefficients of this filter are simple integers (o, or 2), so processing can be performed using only addition, subtraction, and bit shift operations, and it has high-speed and good second-order differential characteristics. Realize. When this filtering operation is applied to the original signal, the peaks of the output signal faithfully indicate the rise time, end time, peak generation/contraction time, and their vicinity of the solution group that makes up the original signal, and some of the zero crossing points are It has the characteristic of showing the vicinity of the inflection point of the original signal. Therefore, the time at which the amplitude value of the filtered output signal crosses the peak and the baseline level (zero level) is detected, and the amplitude value of the original signal that is corrected at the time of occurrence is obtained. This amplitude value becomes the time series signal selected for compressed data generation.

As described above, the amplitude values of the original signal corresponding to the peak and zero-crossing times of the second-order differential filtering output signal are sequentially determined, and the difference between the current amplitude value and the previous, i.e., immediately previous, selected amplitude value is calculated. Time intervals are extracted as pairs, and these pairs are used as compressed data. In the above method, a time interval and an amplitude threshold are set corresponding to the limits that can be displayed as data, and signals exceeding these are also interpolated as the ninth selection signal for compressed data generation. This enables faithful signal reproduction.

To explain this using the electrocardiogram as an example, the electrocardiogram is the second
As shown in the figure, the waves are composed of various liquids called P and QR81T#u waves.Generally, by measuring the time and peak amplitude value of characteristic points called segmentation points in this liquid, A diagnosis is being made. Figure 3 shows the electrocardiogram signal (it) and the result of filtering it (bl). As shown in this figure, the peak time of the filtered output signal coincides with the rise time, end time, and peak occurrence time of each whale wave. Therefore, if the information regarding the occurrence time and amplitude value of the characteristic points of this concentrated solution is stored in the method described above, this information can be reproduced without being lost on the reproduced electrocardiogram signal.

Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention. FIG. 4 is a diagram showing an embodiment of the present invention. To explain the constituent elements, 1 is a second-order differential filter that performs a second-order differential operation on the original signal that has been converted into a sidigital signal. Reference numeral 2 denotes an amplitude level determination device, which discriminates between peak points, zero crossing points, and noise. 3 is a peak detection device that detects peak points. Reference numeral 4 denotes a zero intersection detection device, which detects zero intersections. Reference numeral 65 denotes an original signal reference device, which extracts amplitude value data of the original signal at a certain time. A signal delay device 6 delays the output of the original signal by a certain period of time. 7 is a subtraction device which calculates the difference between the input amplitude value data at each point in time. Reference numeral 8 denotes a voltage-to-hour comparator, which detects an original signal whose voltage-to-hour ratio is above a certain threshold value.

Next, the operation of this method will be described below. Processing 2
The target signal is first subjected to a second-order differential filter IK, and then
A second derivative operation is performed. It is determined whether the second-order differentiated signal is a significant signal that peaks or crosses zero. In the peak detection device 3 and the zero intersection detection device 4, the peak point and zero intersection of the filtering output section are Ia! and detect the time. Next, the amplitude value of the original signal at the detected time is determined by the reference device 5. Next, a subtraction device 7 calculates the difference between the amplitude value of the immediately preceding time series signal, which is the output signal of the delay device 6, and the amplitude value of the current signal obtained above.
, find the difference in amplitude values. This differential amplitude value and delay time are stored as compressed data. On the other hand, for the original signal whose voltage-to-hour ratio exceeds a certain threshold value, the voltage-to-hour comparator 8 separately calculates the difference between the original signal and the output from the delay device 6, so that the original signal can be faithfully reproduced.

The reproduced waveform (bl) and original signal (alt) of a compressed electrocardiogram obtained by applying the present invention to an electrocardiogram signal are shown in FIG.

As described above, according to the MK of the present invention, the following effects can be obtained compared to the conventional system.

are doing.

(2) The second-order differential filter employed in this method can sensitively detect minute level signals, and therefore exhibits good reproducibility even for minute P waves in electrocardiograms.

(3) The second-order differential filter adopted in this method not only has good low-frequency characteristics, but also achieves data compression with excellent reproducibility even for biological signals with superimposed noise.

(4) Since this method has a simple configuration, high-speed data processing such as real-time data compression is possible.

(5) The signal processed and reproduced by this method is smoothed compared to the original signal, and has the same effect as the original signal.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the filtering operation in the present invention, Fig. 2 is a diagram showing an electrocardiogram signal, Fig. 3 is a diagram showing a waveform obtained by second-order differentiation of the electrocardiogram signal, and Fig. 4 is a diagram showing a waveform obtained by second-order differentiation of the electrocardiogram signal. FIG. 5 shows an electrocardiogram waveform reproduced from data compressed according to the present invention.

Claims (1)

[Claims] a filter that applies a second-order differential filtering process to an input signal; means for receiving the filter output and extracting a time sequence in which the filter output satisfies a predetermined condition; and means for measuring the amplitude value of the input signal in the time sequence; means for taking a difference between amplitude values at adjacent times in the time sequence;
A data compression processing device characterized in that the input signal is represented by data indicating the time sequence and data indicating the difference.