Editing Lesson 06 - Adding Sound

To do this, open Cygwin, and type

You should see a long list of filenames scroll by as the package is downloaded.

Now we will switch into the libmad directory and compile the library:

The next bit is a little deviation from the routine we used to install our libraries in Lesson 04. Usually, you could type "make install" and it would automatically install the files to their appropriate directories. Unfortunately, libmad's install script appears to be broken at the moment. Not to worry though, we can install it manually ourselves.

NOTE: There is a space between "./include" and "/usr..." and between "libmad.a" and "/usr..."

Next, download and extract some necessary files into a new project folder. Inside are two files, mp3player.c and mp3player.h which were obtained from John_K's PSPMediaCenter, I made some slight changes to the files as follows (you don't need to do anything with this, it's just in case you were wondering):

//IT IS EXAMPLE CODE

Other than that, it was very clean. John_K has done a great job in porting it.

Now, on to the fun part. Create main.c in your editor of choice, and begin with your comments:

The next little section should be standard to you. The only new includes are the "pspaudio.h" and "pspaudiolib.h." These headers are needed for the audio-specific functions that we will use in our program.

#include <pspctrl.h>

#include <pspdebug.h>

PSP_MODULE_INFO("Mp3 Player Example", 0, 1, 1);

You will also see that we included one of the files that you downloaded, "mp3player.h" (make sure that it's in the same directory as our source file). We also defined printf and did our PSP_MODULE_INFO.

nd now on to what I like to call the twilight zone. I call it that because at this moment, I have no clue how it works or why, but I do intend finding out some day. Anyway, these functions are necessary for your code.

/* Exit callback */

int exit_callback(int arg1, int arg2, void *common) {

           return thid;

}

Now onto the main section of your code. First thing we will do is set the PSP's clock speed to full. Please note that this will not damage your PSP in any way, as it has only been underclocked to this speed by Sony, the reason was most likely battery life (for more information, see Lesson 05. Another notable addition is the "pspAudioInit()" function. This is similar to the "pspDebugScreenInit()" function that we have always called. Basically, it sets up the speakers and everything to be ready to handle our sound output.

           scePowerSetClockFrequency(333, 333, 166);

           pspAudioInit();

           SceCtrlData pad;

Now for the shiny new stuff!

           MP3_Load("test.mp3");

MP3_Init() initialises the structures used by libmad and sets which channel the PSP will be playing back on (in this case, Channel 1). MP3_Load() is pretty self descriptive, it loads your MP3 file (either change this to your MP3 filename or change your MP3 to be called "test.mp3"). MP3_Play() starts the sound playing through the speakers.

he next section shows some options you have, and also acts as a very simple user interface.

           while(1) {

                     sceCtrlReadBufferPositive(&pad, 1);

                               MP3_Stop();

                     }

We read the buttons like we have been doing since Lesson 03. If they push the [X] button, we will exit out of the loop (and effectively, exit out of our program). If the user pushes [O], then we will pause the music using the MP3_Stop() function. Finally, we check the MP3_EndOfStream() function to see if the MP3 file has finished playing. The function will return "1" if it is over and "0" if it's still playing. If it's over, we stop the playback simply so that we're not eating up CPU power when we don't need to.

Then we will enter some wrapup code for after the user exits the loop:

           MP3_FreeTune();

           return 0;

To end our program, we will first stop the MP3, and then release the memory space of the music file we just used. Freeing up memory isn't incredibly important in this program (when the program terminates, the memory will be freed anyway), but it could be important in other homebrew programs. If you don't free the memory, it won't be available for other functions once the MP3 has finished.

The main change is the addition of the our new libraries. "lmad" is for linking libmad for decoding the Mp3. "pspaudiolib" and "pspaudio" give our program access to the PSP's audio hardware (the speakers, for instance).

OBJS = mp3player.o main.o

CFLAGS = -O2 -G0 -Wall

PSP_EBOOT_TITLE = MP3 Player Example

PSPSDK=$(shell psp-config --pspsdk-path)

Now all that's left is to go into Cygwin, find your project folder, and type in the magic word, "make" (or for Firmware Version 1.50 type "make kxploit" to generate your two folders).