key16.s

关于DVD的MPEG2用的DSP代码,在DSP的实现MPEG的压缩,解压算法.

;************************************************************************
; (c)1997 Copyright LuxSonor, Inc. All rights reserved
;
; Revision 1.0
;
;	
;	Module:	 correlation test code
;
;	Initial version:Chialun Lu 12/19/96
;	Modification:	Cecile Foret 02/10/97	
;			Jinshi Huang 12/1/98 for LS388/LS500
;	Calling	:   none
;	Called by:	fir6.S
;				r11: Return Address 
;	Return:		r2 : current delta(in byte) 
;	Param in:   r5 : start location(in byte address) 
;				r0 : number of skipped correlation coefficients 	
;				r1 : number of correlation coefficients computed   		
;	Temp reg:	
;	AGR  reg:
;			AGR0: pointer for goal sequence (copied in part A of mem) 
;			AGR5: pointer for search buffer (in part B of memory)
;			AGR2:
;
;************************************************************************

	.nolist
#include "regdef2.h"
#include "memory2.h"
	.list
	

	.data
	.global SUB_delta_comp		
	
;*********************** begin module "test" **********************
;********* find the correlation ***********************************

SUB_delta_comp:		
	movi	r3,0				; zero the delta
#ifdef	EFFECT
	li	r4,0xff800000			//init to min value
#else	//EFFECT
	movi	r4,0x0000			; zero the r4 maximun cor value
	movi	r18, 0x8			; zero the overflow corresponding to r4
#endif	//EFFECT
	
#ifdef	EFFECT
	mov		AGRAdr5, r5		; set up the start pointer in search
	movi	AGRInc1,8		//skip each other sample
#else	//EFFECT
	mov		AGRAdr3, r5		; set up the start pointer in search
#endif	//EFFECT

	loop	r1,cor2				; r1 = # of corr coeff to be computed

#ifdef	EFFECT
	mulhf	r6, i1,a5(16)		; initialises the correlation computation
//	loop	127,cor1
	loop	63,cor1
	maddhf	r6,i1,a5(16)			; take 1 sample on 4 
cor1:
	add		r5,r0				; increment start pointer in search 
	mov		AGRAdr5, r5			; set up the start pointer in search
#else	//EFFECT
	mulhf	r6, i1, a3(8)		; initialises the correlation computation
	loop	127,cor1
	maddhf	r6,i1,a3(8)			; take 1 sample on 4 
cor1:
	add		r5,r0				; increment start pointer in search 
	mov		AGRAdr3, r5			; set up the start pointer in search
#endif	//EFFECT
	
;********* save the maximun value and location **********************

#ifndef	EFFECT
	tsts	r19,r18
	blt		no_update 
	bgt		Lmax
#endif	//EFFECT
	
	tst		r6, r4
	blte	no_update			

Lmax:
#ifndef	EFFECT
	mov		r18,r19		
#endif	//EFFECT		
	mov		r4, r6				; save the new max
	mov		r2, r3				; save the value of delta
no_update:

;	sub		r6,r6,r4			; compare current and previous max
;	blt		cor_d
;	add		r4,r6				; save the new max. num
;	mov		r2,r3				; save the value of delta
	
;cor_d:
	add		r3,r0				; increment potential value of delta
cor2:		
;	movh	%max_up,r18
;	movh	%max_low, r4 
	nop

	j		r11					; return to main program