/******************************************************************************
* Syntax:
* int QRSFilter(int datum, int init) ;
* Description:
* QRSFilter() takes samples of an ECG signal as input and returns a sample of
* a signal that is an estimate of the local energy in the QRS bandwidth. In
* other words, the signal has a lump in it whenever a QRS complex, or QRS
* complex like artifact occurs. The filters were originally designed for data
* sampled at 200 samples per second, but they work nearly as well at sample
* frequencies from 150 to 250 samples per second.
*
* The filter buffers and static variables are reset if a value other than
* 0 is passed to QRSFilter through init.
*******************************************************************************/
int QRSFilter(int datum, int init)
{
if (init) {
hpfilt(0, 1); // Initialize filters.
lpfilt(0, 1);
mvwint(0, 1);
deriv1(0, 1);
deriv2(0, 1);
}
datum = lpfilt(datum, 0); // Low pass filter data.
datum = hpfilt(datum, 0); // High pass filter data.
datum = deriv2(datum, 0); // Take the derivative.
datum = abs(datum); // Take the absolute value.
datum = mvwint(datum, 0); // Average over an 80 ms window .
return datum;
}
int qrsfilter( int datum, int init )
{
int fdatum ;
//初始化滤波器
if(init)
{
hpfilt( 0, 1 ) ;
lpfilt( 0, 1 ) ;
mvwint( 0, 1 ) ;
deriv1( 0, 1 ) ;
deriv2( 0, 1 ) ;
}
fdatum = lpfilt( datum, 0 ); //低通滤波
fdatum = hpfilt( fdatum, 0 ); //高通滤波
fdatum = deriv2( fdatum, 0 ); //差分滤波
fdatum = abs( fdatum ); //取绝对值
fdatum = mvwint( fdatum, 0 ); //积分窗求和
return(fdatum);
}
