;*****************************************************************************
;
;    DelfMPEG - MPEG audio player for Delfina DSP
;    Copyright (C) 1999  Michael Henke
;
;    This program is free software; you can redistribute it and/or modify
;    it under the terms of the GNU General Public License as published by
;    the Free Software Foundation; either version 2 of the License, or
;    (at your option) any later version.
;
;    This program is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;    GNU General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with this program; if not, write to the Free Software
;    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
;
;*****************************************************************************




;Delfina object DSP56K_PCM
;memory map (for Amiga access)
;
; prog
;   0 .. init (x1=mono, x0=/, y1=freq, y0=/)
;  +2 .. mute (x1=/, x0=/, y1=/, y0=/)
;  +4 .. DelfModule
;
; xdata
;   /
;
; ydata
;   0 .. amybuf (Amiga read)




DELFINA_SAMPLES	equ	1152


	include 'delfequ.inc'

	org	p:

int_key

;->prog
	jmp	init

;->prog+2
	jmp	mute


;->prog+4

;***********************************
;* play routine
;*
;* r1=list of play buffers

	move	y:(r1),r4		;r4=output buf
	move	#rateconv,r3		;r3=rateconv structure
	move	r4,r7			;r7=copy of r4
	move	x:bufptr,r6		;r6=old bufptr

	movec	#DELFINA_SAMPLES*2-1,m2 ;m2=input buffer mask
	jsr	<delf_playrate		;rate conversion

	move	y:mono,b
	tst	b	r7,r0
	jeq	not_mono

	movec	#$ffff,m7
	move	x:(r0)+,a
	rep	#127
	move	x:(r0)+,a	a,y:(r7)+
	move	a,y:(r7)+
not_mono

; Double buffering. We compare old bufptr (in r6) and new bufptr (in r2).
; If they are in different halves of the buffer then interrupt Amiga.
	move	r6,y1			;y1=old pointer
	move	y:buf2,b		;b= start of buf2
	cmp	y1,b	r2,y0		;y0=new pointer
	jle	dbuf_buf2
	cmp	y0,b	y:buf1,x0
	jgt	dbuf_skip
dbuf_int
	move	x0,y:amybuf		;tell amiga the new buffer
	move	#int_key,a0
	move	#causeqw,r0
	jmp	<delf_causeq		;interrupt and exit
dbuf_buf2
	cmp	y0,b	b,x0
	jgt	dbuf_int
dbuf_skip
	rts



;***********************************
;* init stuff
;*
;* x1=mono
;* x0=/
;* y1=freq
;* y0=/
init
	move	#buf,x0
	move	#DELFINA_SAMPLES,a
	add	x0,a	x0,x:bufptr
	move	x0,y:buf1
	move	a,y:buf2
	move	x1,y:mono
	move	y1,x:freq

	rts


;***********************************
;* clear current buffer (pause mode)
;*
;* x1=/
;* x0=/
;* y1=/
;* y0=/
mute
	clr	a	y:amybuf,r0
	move	a,x0
	move	r0,r4
	do	#DELFINA_SAMPLES,mute_loop	;interruptable
	move	a,x:(r0)+	a,y:(r4)+
mute_loop
	rts




	org	l:
	align	4096		;must be >= DELFINA_SAMPLES*2
buf	ds	DELFINA_SAMPLES*2


	org	x:
causeqw	dc	0,0
rateconv
freq	dc	0
bufptr	dc	0
	ds	4
	
	org	y:
;->ydata
amybuf	dc	0		;!!!! Amiga fills this buffer

mono	dc	0		;playing in mono?
buf1	dc	0		;buffer1
buf2	dc	0		;buffer2 = buffer1 + DELFINA_SAMPLES