comparison model/interp.c @ 0:5242703e91d3 tip

Initial checkin for AIM92 aimR8.2 (last updated May 1997).

+/*
+    Copyright (c) Applied Psychology Unit, Medical Research Council. 1988, 1989
+    ===========================================================================
+
+    Permission to use, copy, modify, and distribute this software without fee 
+    is hereby granted for research purposes, provided that this copyright 
+    notice appears in all copies and in all supporting documentation, and that 
+    the software is not redistributed for any fee (except for a nominal shipping 
+    charge). Anyone wanting to incorporate all or part of this software in a
+    commercial product must obtain a license from the Medical Research Council.
+
+    The MRC makes no representations about the suitability of this 
+    software for any purpose.  It is provided "as is" without express or implied 
+    warranty.
+ 
+    THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 
+    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE
+    A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
+    DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN 
+    AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+/*
+    interp.c
+    ========
+
+    Some types of interpolation of short arrays for multiplexed filters
+
+    linterp() performs fast linear interpolations from n points to n*2-1
+    points repeatedly till the number of points required is reached.
+
+    interp() performs a slower but hopefully smoother (in the first differential)
+    interpolation from n points to n*2-1 points.
+
+    Author  : John Holdsworth
+    Written : 11th March, 1989.
+
+    Edited  :
+
+
+
+
+*/
+
+
+#ifndef  lint
+static char *sccs_id = "@(#)interp.c	1.4     J. Holdsworth (MRC-APU)  11/21/89" ;
+#endif
+
+
+/* linear interpolation */
+
+int linterp( input, output, points, newpoints )
+short *input, *output ;
+int points, newpoints ;
+{
+    register int store ;
+    register short *optr, *end, *iptr ;
+    register int nextpoints ;
+
+    nextpoints = points ;
+    end = input + 1 ;
+
+    do {
+
+	iptr = end - 1 + nextpoints - 1 ;
+
+	nextpoints = nextpoints * 2 - 1 ;
+
+	optr = output + nextpoints ;
+	end  = output + 1 ;
+
+	do {
+	    *--optr = store = *  iptr ;
+	    *--optr = store + *--iptr >> 1 ;
+	} while( optr > end ) ;
+
+    } while ( nextpoints < newpoints ) ;
+
+    *--optr = *iptr ;
+
+    return ;
+}
+
+/* simple 2nd orderish interpolation - preserves slopes */
+
+int interp( input, output, points, newpoints )
+short *input, *output ;
+int points, newpoints ;
+{
+    register short *optr, *end, *iptr ;
+    register int nextnum, bignum, oldbignum, oldput ;
+
+    iptr = input  ;
+    optr = output ;
+    end  = output + newpoints ;
+
+#ifdef lint
+    points ;
+#endif
+
+    nextnum   = *(iptr+1) ;
+    oldbignum = ( *iptr << 2 ) + *iptr   ;
+    oldput    = ( *iptr << 1 ) - nextnum ;
+
+    while( optr < end ) {
+	*optr++ = *iptr++ ;
+	if( optr < end ) {
+	    bignum = ( nextnum << 2 ) + nextnum ;
+	    if( optr < end - 2 )
+		nextnum = *(iptr+1) ;
+	    else
+		nextnum = ( *iptr << 1 ) - *(iptr-1) ;
+	    *optr++ = ( oldbignum + bignum - oldput - nextnum + 4 ) >> 3 ;
+	    oldbignum = bignum ;
+	    oldput = *(iptr-1) ;
+	}
+    }
+
+    return ;
+}
+