Mercurial > sdl-ios-xcode
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 |
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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 */ /* 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