hp100.f

lpc 2400 bps语音编解码程序

**********************************************************************
*
*      HP100 Version 55
*
**********************************************************************
*
*    100 Hz High Pass Filter
*
* Jan 92 - corrected typo (1.937148 to 1.935715),
*          rounded coefficients to 7 places,
*          corrected and merged gain (.97466**4),
*          merged numerator into first two sections.
*
	subroutine hp100(speech, start, end)
	integer i, start, end
	real speech(end), si, err
	real z11/0/, z21/0/, z12/0/, z22/0/

	do i = start,end
	    si = speech(i)

	    err = si + 1.859076*z11 - .8648249*z21
	    si = err - 2.00*z11 + z21
	    z21 = z11
	    z11 = err

	    err = si + 1.935715*z12 - .9417004*z22
	    si = err - 2.00*z12 + z22
	    z22 = z12
	    z12 = err

	    speech(i) = .902428*si
	end do

	return
	end