src/audio/dsp/SDL_dspaudio.h
author Sam Lantinga
Fri, 12 Nov 2004 21:39:04 +0000
changeset 968 4675910b0b7b
parent 769 b8d311d90021
child 1312 c9b51268668f
permissions -rw-r--r--
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.
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2004 Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Library General Public
     7     License as published by the Free Software Foundation; either
     8     version 2 of the License, or (at your option) any later version.
     9 
    10     This library is distributed in the hope that it will be useful,
    11     but WITHOUT ANY WARRANTY; without even the implied warranty of
    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13     Library General Public License for more details.
    14 
    15     You should have received a copy of the GNU Library General Public
    16     License along with this library; if not, write to the Free
    17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 #ifdef SAVE_RCSID
    24 static char rcsid =
    25  "@(#) $Id$";
    26 #endif
    27 
    28 #ifndef _SDL_dspaudio_h
    29 #define _SDL_dspaudio_h
    30 
    31 #include "SDL_sysaudio.h"
    32 
    33 /* Hidden "this" pointer for the video functions */
    34 #define _THIS	SDL_AudioDevice *this
    35 
    36 struct SDL_PrivateAudioData {
    37 	/* The file descriptor for the audio device */
    38 	int audio_fd;
    39 
    40 	/* The parent process id, to detect when application quits */
    41 	pid_t parent;
    42 
    43 	/* Raw mixing buffer */
    44 	Uint8 *mixbuf;
    45 	int    mixlen;
    46 };
    47 #define FUDGE_TICKS	10	/* The scheduler overhead ticks per frame */
    48 
    49 /* Old variable names */
    50 #define audio_fd		(this->hidden->audio_fd)
    51 #define parent			(this->hidden->parent)
    52 #define mixbuf			(this->hidden->mixbuf)
    53 #define mixlen			(this->hidden->mixlen)
    54 #define frame_ticks		(this->hidden->frame_ticks)
    55 #define next_frame		(this->hidden->next_frame)
    56 
    57 #endif /* _SDL_dspaudio_h */