Saturday, July 5, 2008

Hello MikMod!

As promised earlier, I've packaged an obligatory example of how to use the iPhone port of libmikmod which I've talked about recently. Go grab this tarball which implements a very simple "Hello World!":
  • It shows how to play a module within a UIKit application. This is an adaptation of the skeleton program found in MikMod Documentation.
  • It shows how to use the higher level sound API Celestial to control mikmod output. For instance, how to react to volume change events when iPhone buttons are pressed.
What to do with this archive once you've extracted it?
  tar -zxf HelloMikMod.tar.gz
  cd HelloMikMod
Simple! Modify the Makefile to set the location of the AudioQueue.h header, as well as the location where you've installed libmikmod. Once you're done, the makefile should look like:
  # directory where AudioQueue.h is located
  # directory where MikMod is located
  # comment the following line when the previous settings are OK for you
  #$(error configure AudioQueue and Mikmod location in the Makefile first)
Then, just build and install the app by typing:
  scp -r root@iphone:/Applications
Where iphone stands for the hostname or the IP of your iPhone. Note that you will need either curl or wget installed or your machine so that the build process is able to download the module played in this example app (fortunately, one of those should always be available on MacOS X or on your favorite Linux distro). For your convenience, the directory is standalone: it contains the app itself linked statically to libmikmod, a launcher descriptor for Springboard and the module to play. For my own pleasure, the mod played is Stardust Memories by Jester / Sanity, my all time favorite Amiga mod (see the compo World of Commodore). This is only a simple example of how to use MikMod on iPhone. I've started implementing a more complex app that mimics the iPod interface for playing mods (Module DB, Screenshot of associated demos...). Now if only I could use Nectarine or DB to make some kind of systematic indexing available!! (sigh....)

Friday, June 27, 2008

MikMod library ported to iPhone

I've always been a big fan of old skool computer music, like chiptunes or demoscene music. Perhaps because they remind me the Good Old Days (tm) of my Amiga. Or perhaps for the same reason I like demoscene: real-time computer art! Because it's definitely cool, I've decided to port MikMod to the iPhone! We'll see later if it might be useful to someone else :) Compiling libmikmod Here are the steps to follow to build libmikmod for your iPhone or iPod Touch. First of all, make sure that you have the necessary header file from Apple, namely AudioQueue.h. This file is part of the AudioQueue framework, which is available in the MacOS X 10.5 SDK. This means that the official iPhone SDK is not required. Then, download the latest libmikmod-3.2.0-beta2 available on the MikMod homepage, as well as this patch for iPhone support. For simplicity, let's consider that both files will be downloaded in the same directory. Once you have them, extract the archive and apply the patch:
tar -zxf libmikmod-3.2.0-beta2.tar.gz
cd libmikmod-3.2.0-beta2
gunzip -cd ../iphone-drv-mikmod-3.2.0-beta2.patch.gz | patch -p1
Among other things, the patch modifies various Makefiles and the configure script, so we have to cleanly regenerate all the autotool-related files:
Now let's set up the necessary environment variables to configure and build libmikmod. First, where to find the AudioQueue header and where to install libmikmod:
export AQDIR=$HOME/local/audioqueue
export MMDIR=$HOME/local/mikmod-iphone
Make sure you are using absolute paths for the variables above. Then, let's set up some compilation flags and name the tools we'll use from the iPhone toolchain:
export LDFLAGS="-framework AudioToolbox"
export CC=arm-apple-darwin-gcc
export RANLIB=arm-apple-darwin-ranlib
Okay, now it's time to let configure do its job:
./configure --enable-iphone --host=arm-apple-darwin --disable-oss --disable-esd --prefix=$MMDIR
We're almost done! But there's still a little quirk that must be addressed. The project is configured to build shared libraries, which for some reason refuse to link with the version of the open-source iPhone toolchain I use. To overcome this problem, you just need to patch the generated libtool configuration. Knowing no clever means to do so, I propose something like:
sed -r -i 's/^(allow_undefined_flag.*)"/\1 -Wl,-read_only_relocs,suppress"/' libtool
Phew, now we're done! Just type:
make install
And voila! a fresh libmikmod with support for your beloved iPhone or iPod Touch! Oh, by the way: the library comes in both static and dynamic flavor, so it should be pretty usable. Of course, the obligatory example will follow soon :P EDIT: the link to the patch was pointing to a plain file instead of a gzip one, fixed!

Thursday, June 19, 2008

Hello World!

I'm opening this blog to share my bits of code, hacks or thoughts I have during the time I spend in front of my computer. That will be a great occasion for me to retrieve all the goodies laying in my attic and that I should take the time to package cleanly! Moreover, that will be a good way of talking about the cool things I work on nowadays... Okay, I know... it sounds so vague... but hey, it's only a Hello World after all :)