view include/SDL_joystick.h @ 942:41a59de7f2ed

Here are patches for SDL12 and SDL_mixer for 4 or 6 channel surround sound on Linux using the Alsa driver. To use them, naturally you need a sound card that will do 4 or 6 channels and probably also a recent version of the Alsa drivers and library. Since the only SDL output driver that knows about surround sound is the Alsa driver, you���ll want to choose it, using: export SDL_AUDIODRIVER=alsa There are no syntactic changes to the programming API. No new library calls, no differences in arguments. There are two semantic changes: (1) For library calls with number of channels as an argument, formerly you could use only 1 or 2 for the number of channels. Now you can also use 4 or 6. (2) The two "left" and "right" arguments to Mix_SetPanning, for the case of 4 or 6 channels, no longer simply control the volumes of the left and right channels. Now the "left" argument is converted to an angle and Mix_SetPosition is called, and the "right" argu- ment is ignored. With two exceptions, so far as I know, the modified SDL12 and SDL_mixer work the same way as the original versions, when opened for 1 or 2 channel output. The two exceptions are bugs which I fixed. Well, the first, anyway, is a bug for sure. When rate conversions up or down by a factor of two are applied (in src/audio/SDL_audiocvt.c), streams with different numbers of channels (that is, mono and stereo) are treated the same way: either each sample is copied or every other sample is omitted. This is ok for mono, but for stereo, it is frames that should be copied or omitted, where by "frame" I mean a portion of the stream containing one sample for each channel. (In the SDL source, confusingly, sometimes frames are called "samples".) So for these rate conversions, stereo streams have to be treated differently, and they are, in my modified version. The other problem that might be characterized as a bug arises when SDL_mixer is passed a multichannel chunk which does not have an integral number of frames. Due to the way the effect_position code loops over frames, when the chunk ends with a partial frame, memory outside the chunk buffer will be accessed. In the case of stereo, it���s possible that because malloc may give more memory than requested, this potential problem never actually causes a segment fault. I don���t know. For 6 channel chunks, I do know, and it does cause segment faults. If SDL_mixer is passed defective chunks and this causes a segment fault, arguably, that���s not a bug in SDL_mixer. Still, whether or not it counts as a bug, it���s easy to protect against, so why not? I added code in mixer.c to discard any partial frame at the end of a chunk. Then what about when SDL or SDL_mixer is opened for 4 or 6 chan- nel output? What happens with the parts of the current library designed for stereo? I don���t know whether I���ve covered all the bases, but I���ve tried: (1) For playing 2 channel waves, or other cases where SDL knows it has to match up a 2 channel source with a 4 or 6 channel output, I���ve added code in SDL_audiocvt.c to make the necessary conversions. (2) For playing midis using timidity, I���ve converted timidity to do 4 or 6 channel output, upon request. (3) For playing mods using mikmod, I put ad hoc code in music.c to convert the stereo output that mikmod produces to 4 or 6 chan- nels. Obviously it would be better to change the mikmod code to mix down into 4 or 6 channels, but I have a hard time following the code in mikmod, so I didn���t do that. (4) For playing mp3s, I put ad hoc code in smpeg to copy channels in the case when 4 or 6 channel output is needed. (5) There seems to be no problem with .ogg files - stereo .oggs can be up converted as .wavs are. (6) The effect_position code in SDL_mixer is now generalized to in- clude the cases of 4 and 6 channel streams. I���ve done a very limited amount of compatibility testing for some of the games using SDL I happen to have. For details, see the file TESTS. I���ve put into a separate archive, Surround-SDL-testfiles.tgz, a couple of 6 channel wave files for testing and a 6 channel ogg file. If you have the right hardware and version of Alsa, you should be able to play the wave files with the Alsa utility aplay (and hear all channels, except maybe lfe, for chan-id.wav, since it���s rather faint). Don���t expect aplay to give good sound, though. There���s something wrong with the current version of aplay. The canyon.ogg file is to test loading of 6 channel oggs. After patching and compiling, you can play it with playmus. (My version of ogg123 will not play it, and I had to patch mplayer to get it to play 6 channel oggs.) Greg Lee <greg@ling.lll.hawaii.edu> Thus, July 1, 2004
author Sam Lantinga <slouken@libsdl.org>
date Sat, 21 Aug 2004 12:27:02 +0000
parents e6ceebb0f0eb
children c9b51268668f
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 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
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

/* Include file for SDL joystick event handling */

#ifndef _SDL_joystick_h
#define _SDL_joystick_h

#include "SDL_types.h"

#include "begin_code.h"
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
extern "C" {
#endif

/* In order to use these functions, SDL_Init() must have been called
   with the SDL_INIT_JOYSTICK flag.  This causes SDL to scan the system
   for joysticks, and load appropriate drivers.
*/

/* The joystick structure used to identify an SDL joystick */
struct _SDL_Joystick;
typedef struct _SDL_Joystick SDL_Joystick;


/* Function prototypes */
/*
 * Count the number of joysticks attached to the system
 */
extern DECLSPEC int SDLCALL SDL_NumJoysticks(void);

/*
 * Get the implementation dependent name of a joystick.
 * This can be called before any joysticks are opened.
 * If no name can be found, this function returns NULL.
 */
extern DECLSPEC const char * SDLCALL SDL_JoystickName(int device_index);

/*
 * Open a joystick for use - the index passed as an argument refers to
 * the N'th joystick on the system.  This index is the value which will
 * identify this joystick in future joystick events.
 *
 * This function returns a joystick identifier, or NULL if an error occurred.
 */
extern DECLSPEC SDL_Joystick * SDLCALL SDL_JoystickOpen(int device_index);

/*
 * Returns 1 if the joystick has been opened, or 0 if it has not.
 */
extern DECLSPEC int SDLCALL SDL_JoystickOpened(int device_index);

/*
 * Get the device index of an opened joystick.
 */
extern DECLSPEC int SDLCALL SDL_JoystickIndex(SDL_Joystick *joystick);

/*
 * Get the number of general axis controls on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumAxes(SDL_Joystick *joystick);

/*
 * Get the number of trackballs on a joystick
 * Joystick trackballs have only relative motion events associated
 * with them and their state cannot be polled.
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumBalls(SDL_Joystick *joystick);

/*
 * Get the number of POV hats on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumHats(SDL_Joystick *joystick);

/*
 * Get the number of buttons on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumButtons(SDL_Joystick *joystick);

/*
 * Update the current state of the open joysticks.
 * This is called automatically by the event loop if any joystick
 * events are enabled.
 */
extern DECLSPEC void SDLCALL SDL_JoystickUpdate(void);

/*
 * Enable/disable joystick event polling.
 * If joystick events are disabled, you must call SDL_JoystickUpdate()
 * yourself and check the state of the joystick when you want joystick
 * information.
 * The state can be one of SDL_QUERY, SDL_ENABLE or SDL_IGNORE.
 */
extern DECLSPEC int SDLCALL SDL_JoystickEventState(int state);

/*
 * Get the current state of an axis control on a joystick
 * The state is a value ranging from -32768 to 32767.
 * The axis indices start at index 0.
 */
extern DECLSPEC Sint16 SDLCALL SDL_JoystickGetAxis(SDL_Joystick *joystick, int axis);

/*
 * Get the current state of a POV hat on a joystick
 * The return value is one of the following positions:
 */
#define SDL_HAT_CENTERED	0x00
#define SDL_HAT_UP		0x01
#define SDL_HAT_RIGHT		0x02
#define SDL_HAT_DOWN		0x04
#define SDL_HAT_LEFT		0x08
#define SDL_HAT_RIGHTUP		(SDL_HAT_RIGHT|SDL_HAT_UP)
#define SDL_HAT_RIGHTDOWN	(SDL_HAT_RIGHT|SDL_HAT_DOWN)
#define SDL_HAT_LEFTUP		(SDL_HAT_LEFT|SDL_HAT_UP)
#define SDL_HAT_LEFTDOWN	(SDL_HAT_LEFT|SDL_HAT_DOWN)
/*
 * The hat indices start at index 0.
 */
extern DECLSPEC Uint8 SDLCALL SDL_JoystickGetHat(SDL_Joystick *joystick, int hat);

/*
 * Get the ball axis change since the last poll
 * This returns 0, or -1 if you passed it invalid parameters.
 * The ball indices start at index 0.
 */
extern DECLSPEC int SDLCALL SDL_JoystickGetBall(SDL_Joystick *joystick, int ball, int *dx, int *dy);

/*
 * Get the current state of a button on a joystick
 * The button indices start at index 0.
 */
extern DECLSPEC Uint8 SDLCALL SDL_JoystickGetButton(SDL_Joystick *joystick, int button);

/*
 * Close a joystick previously opened with SDL_JoystickOpen()
 */
extern DECLSPEC void SDLCALL SDL_JoystickClose(SDL_Joystick *joystick);


/* Ends C function definitions when using C++ */
#ifdef __cplusplus
}
#endif
#include "close_code.h"

#endif /* _SDL_joystick_h */