Mercurial > sdl-ios-xcode
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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 | ae4ab3ac89a9 |
children | 3d9a199d2a70 |
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============================================================================== Using the Simple DirectMedia Layer with Mac OS X ============================================================================== These instructions are for people using Apple's Mac OS X (pronounced "ten"). From the developer's point of view, OS X is a sort of hybrid Mac and Unix system, and you have the option of using either traditional command line tools or Apple's IDE ProjectBuilder (PB). To build SDL using the command line, use the standard configure and make process: ./configure make sudo make install (You may need to create the subdirs of /usr/local manually.) To use the library once it's built, you essential have two possibilities: use the traditional autoconf/automake/make method, or use Project Builder. ============================================================================== Using the Simple DirectMedia Layer with a traditional Makefile ============================================================================== An existing autoconf/automake build system for your SDL app has good chances to work almost unchanged on OS X. However, to produce a "real" MacOS X binary that you can distribute to users, you need to put the generated binary into a so called "bundle", which basically is a fancy folder with a name like "MyCoolGame.app". To get this build automatically, add something like the following rule to your Makefile.am: bundle_contents = APP_NAME.app/Contents APP_NAME_bundle: EXE_NAME mkdir -p $(bundle_contents)/MacOS mkdir -p $(bundle_contents)/Resources echo "APPL????" > $(bundle_contents)/PkgInfo $(INSTALL_PROGRAM) $< $(bundle_contents)/MacOS/ You should replace EXE_NAME with the name of the executable. APP_NAME is what will be visible to the user in the Finder. Usually it will be the same as EXE_NAME but capitalized. E.g. if EXE_NAME is "testgame" then APP_NAME usually is "TestGame". You might also want to use @PACKAGE@ to use the package name as specified in your configure.in file. If your project builds more than one application, you will have to do a bit more. For each of your target applications, you need a seperate rule. If you want the created bundles to be installed, you may want to add this rule to your Makefile.am: install-exec-hook: APP_NAME_bundle rm -rf $(DESTDIR)$(prefix)/Applications/APP_NAME.app mkdir -p $(DESTDIR)$(prefix)/Applications/ cp -r $< /$(DESTDIR)$(prefix)Applications/ This rule takes the Bundle created by the rule from step 3 and installs them into $(DESTDIR)$(prefix)/Applications/. Again, if you want to install multiple applications, you will have to augment the make rule accordingly. But beware! That is only part of the story! With the above, you end up with a bare bone .app bundle, which is double clickable from the Finder. But there are some more things you should do before shipping yor product... 1) The bundle right now probably is dynamically linked against SDL. That means that when you copy it to another computer, *it will not run*, unless you also install SDL on that other computer. A good solution for this dilemma is to static link against SDL. On OS X, you can achieve that by linkinag against the libraries listed by sdl-config --static-libs instead of those listed by sdl-config --libs Depending on how exactly SDL is integrated into your build systems, the way to achieve that varies, so I won't describe it here in detail 2) Add an 'Info.plist' to your application. That is a special XML file which contains some meta-information about your application (like some copyright information, the version of your app, the name of an optional icon file, and other things). Part of that information is displayed by the Finder when you click on the .app, or if you look at the "Get Info" window. More information about Info.plist files can be found on Apple's homepage. As a final remark, let me add that I use some of the techniques (and some variations of them) in Exult and ScummVM; both are available in source on the net, so feel free to take a peek at them for inspiration! ============================================================================== Using the Simple DirectMedia Layer with Project Builder ============================================================================== These instructions are for using Apple's Project Builder IDE to build SDL applications. - First steps The first thing to do is to unpack the PBProjects.tar.gz archive in the top level SDL directory (where the PBProjects.tar.gz archive resides). Because Stuffit Expander will unpack the archive into a subdirectory, you should unpack the archive manually from the command line: cd [path_to_SDL_source] tar zxf PBProjects.tar.gz This will create a new folder called PBProjects, which you can browse normally from the Finder. - Building the Framework The SDL Library is packaged as a framework bundle, an organized relocatable folder heirarchy of executible code, interface headers, and additional resources. For practical purposes, you can think of a framework as a more user and system-friendly shared library, whose library file behaves more or less like a standard UNIX shared library. To build the framework, simply open the framework project and build it. By default, the framework bundle "SDL.framework" is installed in ~/Library/Frameworks. Therefore, the testers and project stationary expect it to be located there. However, it will function the same in any of the following locations: ~/Library/Frameworks /Local/Library/Frameworks /System/Library/Frameworks - Build Options There are two "Build Styles" (See the "Targets" tab) for SDL. "Deployment" should be used if you aren't tweaking the SDL library. "Development" should be used to debug SDL apps or the library itself. - Building the Testers Open the SDLTest project and build away! - Using the Project Stationary Copy the stationary to the indicated folders to access it from the "New Project" and "Add target" menus. What could be easier? - Setting up a new project by hand Some of you won't want to use the Stationary so I'll give some tips: * Create a new "Cocoa Application" * Add src/main/macosx/SDLMain.m , .h and .nib to your project * Remove "main.c" from your project * Remove "MainMenu.nib" from your project * Add "$(HOME)/Library/Frameworks/SDL.framework/Headers" to include path * Add "$(HOME)/Library/Frameworks" to the frameworks search path * Add "-framework SDL -framework Foundation -framework AppKit" to "OTHER_LDFLAGS" * Set the "Main Nib File" under "Application Settings" to "SDLMain.nib" * Add your files * Clean and build - Building from command line Use pbxbuild in the same directory as your .pbproj file - Running your app You can send command line args to your app by either invoking it from the command line (in *.app/Contents/MacOS) or by entering them in the "Executibles" panel of the target settings. - Implementation Notes Some things that may be of interest about how it all works... * Working directory As defined in the SDL_main.m file, the working directory of your SDL app is by default set to its parent. You may wish to change this to better suit your needs. * You have a Cocoa App! Your SDL app is essentially a Cocoa application. When your app starts up and the libraries finish loading, a Cocoa procedure is called, which sets up the working directory and calls your main() method. You are free to modify your Cocoa app with generally no consequence to SDL. You cannot, however, easily change the SDL window itself. Functionality may be added in the future to help this. Known bugs are listed in the file "BUGS"