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Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST) From: Hannu Savolainen Subject: Re: SDL uses obsolete OSS features I did some work on getting OSS to work better with SDL. There have been some problems with select which should be fixed now. I'm having some problems in understanding what is the purpose of the DSP_WaitAudio() routine. I added a return to the very beginning of this routine and commendted out the define for USE_BLOCKING_WRITES. At least lbreakout2 seems to work as well as earlier. The latencies are the same. An ordinary blocking write does exactly the same thing than DSP_WaitAudio does. So I would recommend using the USE_BLOCKING_WRITES approach and removing everything from the DSP_WaitAudio routine. Also enabling USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because you don't need to handle the partial writes (the do-while loop). Attached is a patch against SDL-1.2.7. After these changes SDL will use OSS as it's designed to be used (make it as simple as possible). This code should work with all OSS implementations because it uses only the very fundamental features that have been there since the jurassic times.
author Sam Lantinga <slouken@libsdl.org>
date Fri, 12 Nov 2004 21:39:04 +0000
parents 185acc07127a
children d00b4d8508ab
line wrap: on
line source

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

/*
	Audio interrupts

	Patrice Mandin, Didier Méquignon
 */

	.text

	.globl	_SDL_MintAudio_Callback

	.globl	_SDL_MintAudio_GsxbInterrupt
	.globl	_SDL_MintAudio_EmptyGsxbInterrupt
	.globl	_SDL_MintAudio_XbiosInterrupt
	.globl	_SDL_MintAudio_XbiosInterruptMeasureClock
	.globl	_SDL_MintAudio_Dma8Interrupt
	.globl	_SDL_MintAudio_StfaInterrupt

	.globl	_SDL_MintAudio_mutex
	.globl	_SDL_MintAudio_audiobuf
	.globl	_SDL_MintAudio_numbuf
	.globl	_SDL_MintAudio_audiosize
	.globl	_SDL_MintAudio_clocktics

	.globl	_SDL_MintAudio_stfa

/*
	How it works:
	- Audio is playing buffer #0 (resp. #1)
	- We must calculate a sample in buffer #1 (resp. #0)
	  so we first call the callback to do it
	- Then we swap the buffers
*/

/*--- GSXB interrupt vector ---*/

	.text
_SDL_MintAudio_GsxbInterrupt:

	/* Check if we are not already running */
	tstw	_SDL_MintAudio_mutex
	bnes	_SDL_MintAudio_EmptyGsxbInterrupt
	notw	_SDL_MintAudio_mutex
	
	/* Swap buffers */
	eorw	#1,_SDL_MintAudio_numbuf

	moveml	d0-d2/a0-a2,sp@-

	/* Callback */
	jsr	_SDL_MintAudio_Callback

	/* Set new buffer */

	moveq	#0,d0
	movel	_SDL_MintAudio_audiosize,d1

	movew	_SDL_MintAudio_numbuf,d0
	lsll	#2,d0
	lea	_SDL_MintAudio_audiobuf,a0
	movel	a0@(d0:l),a1

	lea	a1@(d1:l),a2

	movel	a2,sp@-
	movel	a1,sp@-
	clrw	sp@-
	movew	#131,sp@-
	trap	#14
	lea	sp@(12),sp

	moveml	sp@+,d0-d2/a0-a2

	clrw	_SDL_MintAudio_mutex
_SDL_MintAudio_EmptyGsxbInterrupt:
	rts

/*--- Xbios interrupt vector to measure Falcon external clock ---*/

_SDL_MintAudio_XbiosInterruptMeasureClock:          /* 1 mS */

	btst	#0,0xFFFF8901:w	/* state DMA sound */
	beqs	SDL_MintAudio_EndIntMeasure
	addql	#1,_SDL_MintAudio_clocktics
SDL_MintAudio_EndIntMeasure:
	bclr	#5,0xFFFFFA0F:w	/* Clear service bit */
	rte

/*--- Xbios interrupt vector ---*/

_SDL_MintAudio_XbiosInterrupt:

	/* Reenable interrupts, so other interrupts can work */
	movew	#0x2300,sr

	/* Clear service bit, so other MFP interrupts can work */
	bclr	#5,0xfffffa0f:w

	/* Check if we are not already running */
	tstw	_SDL_MintAudio_mutex
	bnes	SDL_MintAudio_XbiosEnd
	notw	_SDL_MintAudio_mutex
	
	/* Swap buffers */
	eorw	#1,_SDL_MintAudio_numbuf

	moveml	d0-d2/a0-a2,sp@-

	/* Callback */
	jsr	_SDL_MintAudio_Callback

	/* Set new buffer */

	moveq	#0,d0
	movel	_SDL_MintAudio_audiosize,d1

	movew	_SDL_MintAudio_numbuf,d0
	lsll	#2,d0
	lea	_SDL_MintAudio_audiobuf,a0
	movel	a0@(d0:l),a1

	lea	a1@(d1:l),a2

	movel	a2,sp@-
	movel	a1,sp@-
	clrw	sp@-
	movew	#131,sp@-
	trap	#14
	lea	sp@(12),sp

	moveml	sp@+,d0-d2/a0-a2

	clrw	_SDL_MintAudio_mutex
SDL_MintAudio_XbiosEnd:
	rte

/*--- DMA 8 bits interrupt vector ---*/

_SDL_MintAudio_Dma8Interrupt:

	/* Reenable interrupts, so other interrupts can work */
	movew	#0x2300,sr

	/* Clear service bit, so other MFP interrupts can work */
	bclr	#5,0xfffffa0f:w

	/* Check if we are not already running */
	tstw	_SDL_MintAudio_mutex
	bnes	SDL_MintAudio_Dma8End
	notw	_SDL_MintAudio_mutex
	
	/* Swap buffers */
	eorw	#1,_SDL_MintAudio_numbuf

	moveml	d0-d1/a0-a1,sp@-

	/* Callback */
	jsr	_SDL_MintAudio_Callback

	/* Set new buffer */

	moveq	#0,d0

	movew	_SDL_MintAudio_numbuf,d0
	lslw	#2,d0
	lea	_SDL_MintAudio_audiobuf,a0
	movel	a0@(d0:w),d1

	/* Modify DMA addresses */
	lea	0xffff8900:w,a0

	moveb	d1,a0@(0x07)	/* Start address */
	rorl	#8,d1
	moveb	d1,a0@(0x05)
	rorl	#8,d1
	moveb	d1,a0@(0x03)
	swap	d1

	addl	_SDL_MintAudio_audiosize,d1

	moveb	d1,a0@(0x13)	/* End address */
	rorl	#8,d1
	moveb	d1,a0@(0x11)
	rorl	#8,d1
	moveb	d1,a0@(0x0f)

	moveml	sp@+,d0-d1/a0-a1

	clrw	_SDL_MintAudio_mutex
SDL_MintAudio_Dma8End:
	rte

/*--- STFA interrupt vector ---*/

STFA_SOUND_START	=	6
STFA_SOUND_END		=	STFA_SOUND_START+8

_SDL_MintAudio_StfaInterrupt:

	/* Reenable interrupts, so other interrupts can work */
	movew	#0x2300,sr

	/* Check if we are not already running */
	tstw	_SDL_MintAudio_mutex
	bnes	SDL_MintAudio_StfaEnd
	notw	_SDL_MintAudio_mutex
	
	/* Swap buffers */
	eorw	#1,_SDL_MintAudio_numbuf

	moveml	d0-d1/a0-a1,sp@-

	/* Callback */
	jsr	_SDL_MintAudio_Callback

	/* Set new buffer */

	moveq	#0,d0
	movel	_SDL_MintAudio_stfa,a1

	movew	_SDL_MintAudio_numbuf,d0
	lslw	#2,d0
	lea	_SDL_MintAudio_audiobuf,a0
	movel	a0@(d0:w),d1

	/* Modify STFA replay buffers */
	movel	d1,a1@(STFA_SOUND_START)
	addl	_SDL_MintAudio_audiosize,d1
	movel	d1,a1@(STFA_SOUND_END)

	moveml	sp@+,d0-d1/a0-a1

	clrw	_SDL_MintAudio_mutex
SDL_MintAudio_StfaEnd:
	rte