view src/cdrom/macos/SDL_syscdrom_c.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 b8d311d90021
children d910939febfa
line wrap: on
line source

/*
    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
*/

/* This is the MacOS specific header for the SDL CD-ROM API
   Contributed by Matt Slot
 */

/* AppleCD Control calls */
#define kVerifyTheDisc   	  5		/* Returns noErr if there is disc inserted */
#define kEjectTheDisc   	  7		/* Eject disc from drive */
#define kUserEject    		 80		/* Enable/disable the CD-ROM eject button */
#define kReadTOC    		100		/* Extract various TOC information from the disc */
#define kReadQ   			101		/* Extract Q subcode info for the current track */
#define kAudioTrackSearch   103		/* Start playback from the indicated position */
#define kAudioPlay    		104		/* Start playback from the indicated position */
#define kAudioPause    		105		/* Pause/continue the playback */
#define kAudioStop    		106		/* Stop playback at the indicated position */
#define kAudioStatus    	107		/* Return audio play status */
#define kAudioControl    	109		/* Set the output volume for the audio channels */
#define kReadAudioVolume   	112		/* Get the output volume for the audio channels */
#define kSetTrackList   	122		/* Set the track program for the audio CD to play */
#define kGetTrackList   	123		/* Get the track program the audio CD is playing */
#define kGetTrackIndex   	124		/* Get the track index the audio CD is playing */
#define kSetPlayMode   		125		/* Set the audio tracks play mode */
#define kGetPlayMode   		126		/* Get the audio tracks play mode */

/* AppleCD Status calls */
#define kGetDriveType   	 96		/* Get the type of the physical CD-ROM drive */
#define kWhoIsThere    		 97		/* Get a bitmap of SCSI IDs the driver controls */
#define kGetBlockSize    	 98		/* Get current block size of the CD-ROM drive */
	
/* AppleCD other constants */
#define kBlockPosition    	  0		/* Position at the specified logical block number */
#define kAbsMSFPosition    	  1		/* Position at the specified Min/Sec/Frame (in BCD) */
#define kTrackPosition    	  2		/* Position at the specified track number (in BCD) */
#define kIndexPosition    	  3		/* Position at the nth track in program (in BCD) */

#define kMutedPlayMode   	  0		/* Play the audio track with no output */
#define kStereoPlayMode   	  9		/* Play the audio track in normal stereo */

#define kControlFieldMask  	0x0D	/* Bits 3,2,0 in the nibble */
#define kDataTrackMask   	0x04	/* Indicates Data Track */

#define kGetTrackRange    	  1		/* Query TOC for track numbers */
#define kGetLeadOutArea    	  2		/* Query TOC for "Lead Out" end of audio data */
#define kGetTrackEntries   	  3		/* Query TOC for track starts and data types */

#define kStatusPlaying		  0		/* Audio Play operation in progress */
#define kStatusPaused		  1		/* CD-ROM device in Hold Track ("Pause") state */
#define kStatusMuted		  2		/* MUTING-ON operation in progress */
#define kStatusDone			  3		/* Audio Play completed */
#define kStatusError		  4		/* Error occurred during audio play operation */
#define kStatusStopped		  5		/* Audio play operation not requested */

#define kPlayModeSequential	  0		/*  Play tracks in order */
#define kPlayModeShuffled	  1		/* Play tracks randomly */
#define kPlayModeProgrammed   2		/* Use custom playlist */

/* AppleCD Gestalt selectors */
#define kGestaltAudioCDSelector    'aucd'
#define kDriverVersion52   		0x00000520
#define kDriverVersion51   		0x00000510
#define kDriverVersion50   		0x00000500

/* Drive type constants */
#define kDriveAppleCD_SC   				  1
#define kDriveAppleCD_SCPlus_or_150   	  2
#define kDriveAppleCD_300_or_300Plus   	  3

/* Misc constants */
#define kFirstSCSIDevice   	 -33
#define kLastSCSIDevice    	 -40

#if PRAGMA_STRUCT_ALIGN
	#pragma options align=mac68k
#endif

/* AppleCD driver parameter block */
typedef struct CDCntrlParam {
	QElemPtr				qLink;
	short					qType;
	short					ioTrap;
	Ptr						ioCmdAddr;
	IOCompletionUPP			ioCompletion;
	OSErr					ioResult;
	StringPtr				ioNamePtr;
	short					ioVRefNum;
	short					ioCRefNum;
	short					csCode;
	
	union {
		long				longs[6];
		short				words[11];
		unsigned char		bytes[22];
		struct {
			unsigned char	status;
			unsigned char	play;
			unsigned char	control;
			unsigned char	minute;
			unsigned char	second;
			unsigned char	frame;
			} cd;
		} csParam;

	} CDCntrlParam, *CDCntrlParamPtr;

typedef union CDTrackData {
	long				value;			/* Treat as a longword value */
	struct {
		unsigned char	reserved : 4;	/* Unused by AppleCD driver  */
		unsigned char	control : 4;	/* Track flags (data track?) */
		unsigned char	min;			/* Start of track (BCD)      */
		unsigned char	sec;			/* Start of track (BCD)      */
		unsigned char	frame;			/* Start of track (BCD)      */
		} entry;						/* Broken into fields        */
	} CDTrackData, *CDTrackPtr;
	
#if PRAGMA_STRUCT_ALIGN
	#pragma options align=reset
#endif