************************************************************************	IVFILT Version 48*************************************************************************   2nd order inverse filter, speech is decimated 4:1** Inputs:*  LEN    - Length of speech buffers*  NSAMP  - Number of samples to filter*  LPBUF  - Low pass filtered speech buffer* Output:*  IVBUF  - Inverse filtered speech buffer*  IVRC   - Inverse filter reflection coefficients (for voicing)*	SUBROUTINE IVFILT( LPBUF, IVBUF, LEN, NSAMP, IVRC )	INTEGER LEN, NSAMP, I, J, K	REAL IVBUF(LEN), LPBUF(LEN)	REAL R(3), PC1, PC2, IVRC(2)*  Calculate Autocorrelations	DO I = 1,3	   R(I) = 0.	   K = 4*(I-1)	   DO J = I*4+LEN-NSAMP,LEN,2	      R(I) = R(I) + LPBUF(J)*LPBUF(J-K)	   END DO	END DO*  Calculate predictor coefficients	PC1 = 0.	PC2 = 0.	IVRC(1) = 0.	IVRC(2) = 0.	IF (R(1) .GT. 1.0E-10) THEN	   IVRC(1) = R(2)/R(1)	   IVRC(2) = (R(3)-IVRC(1)*R(2)) / (R(1)-IVRC(1)*R(2))	   PC1 = IVRC(1) - IVRC(1)*IVRC(2)	   PC2 = IVRC(2)	END IF*  Inverse filter LPBUF into IVBUF	DO I = LEN+1-NSAMP,LEN	   IVBUF(I) = LPBUF(I) - PC1*LPBUF(I-4) - PC2*LPBUF(I-8)	END DO	RETURN	END