I've searched the net, I've searched here. I've found code that I could compile and it works fine, but for some reason my code won't produce any sound. I'm porting an old game to the PC (Windows,) and I'm trying to make it as authentic as possible, so I'm wanting to use generated wave forms. I've pretty much copied and pasted the working code (only adding in multiple voices,) and it still won't work (even thought the exact same code for a single voice works fine.) I know I'm missing something obvious, but I just cannot figure out what. Any help would be appreciated thank you.
First some notes... I was looking for something that would allow me to use the original methodology. The original system used paired bytes for music (sound effects - only 2 - were handled in code.) A time byte that counted down every time the routine was called, and a note byte that was played until time reached zero. this was done by patching into the interrupt vector, windows doesn't allow that, so I set up a timer that routing that accomplished the same thing. The timer kicks in, updates the display, and then runs the music sequence. I set this up with a defined time so that I only have one place to adjust the timing at (to get it as close as possible to the original sequence. The music is a generated wave form (and I've double checked the math, and even examined the generated data in debug mode,) and it looks good. The sequence looks good, but doesn't actually produce sound. I tried SDL2 first, and it's method of only playing 1 sound doesn't work for me, also, unless I make the sample duration extremely short (and the sound produced this way is awful,) I can't match the timing (it plays the entire sample through it's own interrupt without letting me make adjustments.) Also, blending the 3 voices together (when they all run with different timings,) is a mess. Most of the other engines I examined work in much the same way, they want to use their own callback interrupt and won't allow me to tweak it appropriately. This is why I started working with OpenAL. It allows multiple voices (sources,) and allows me to set the timings myself. On advice from several forums, I set it up so that the sample lengths are all multiples of full cycles. Anyway, here's the code.
int main(int argc, char* argv[])
{
FreeConsole(); //Get rid of the DOS console, don't need it
if (InitLog() < 0) return -1; //Start logging
UINT_PTR tim = NULL;
SDL_Event event;
InitVideo(false); //Set to window for now, will put options in later
curmusic = 5;
InitAudio();
SetTimer(NULL,tim,_FREQ_,TimerProc);
SDL_PollEvent(&event);
while (event.type != SDL_KEYDOWN) SDL_PollEvent(&event);
SDL_Quit();
return 0;
}
void CALLBACK TimerProc(HWND hWind, UINT Msg, UINT_PTR idEvent, DWORD dwTime)
{
RenderOutput();
PlayMusic();
//UpdateTimer();
//RotateGate();
return;
}
void InitAudio(void)
{
ALCdevice *dev;
ALCcontext *cxt;
Log("Initializing OpenAL Audio\r\n");
dev = alcOpenDevice(NULL);
if (!dev) {
Log("Failed to open an audio device\r\n");
exit(-1);
}
cxt = alcCreateContext(dev, NULL);
alcMakeContextCurrent(cxt);
if(!cxt) {
Log("Failed to create audio context\r\n");
exit(-1);
}
alGenBuffers(4,Buffer);
if (alGetError() != AL_NO_ERROR) {
Log("Error during buffer creation\r\n");
exit(-1);
}
alGenSources(4, Source);
if (alGetError() != AL_NO_ERROR) {
Log("Error during source creation\r\n");
exit(-1);
}
return;
}
void PlayMusic()
{
static int oldsong, ofset, mtime[4];
double freq;
ALuint srate = 44100;
ALuint voice, i, note, len, hold;
short buf[4][_BUFFSIZE_];
bool test[4] = {false, false, false, false};
if (curmusic != oldsong) {
oldsong = (int)curmusic;
if (curmusic > 0)
ofset = moffset[(curmusic - 1)];
for (voice = 1; voice < 4; voice++)
alSourceStop(Source[voice]);
mtime[voice] = 0;
return;
}
if (curmusic == 0) return;
//Only 3 voices for music, but have
for (voice = 0; voice < 3; voice ++) { // 4 set asside for eventual sound effects
if (mtime[voice] == 0) { //is note finished
alSourceStop(Source[voice]); //It is, so stop the channel (source)
mtime[voice] = music[ofset++]; //Get the next duration
if (mtime[voice] == 0) {oldsong = 0; return;} //zero marks end, so restart
note = music[ofset++]; //Get the next note
if (note > 127) { //Old HW data was designed for could only
if (note == 255) note = 127; //use values 128 - 255 (255 = 127)
freq = (15980 / (voice + (int)(voice / 3))) / (256 - note); //freq of note
len = (ALuint)(srate / freq); //A single cycle of that freq.
hold = len;
while (len < (srate / (1000 / _FREQ_))) len += hold; //Multiply till 1 interrup cycle
while (len > _BUFFSIZE_) len -= hold; //Don't overload buffer
if (len == 0) len = _BUFFSIZE_; //Just to be safe
for (i = 0; i < len; i++) //calculate sine wave and put in buffer
buf[voice][i] = (short)((32760 * sin((2 * M_PI * i * freq) / srate)));
alBufferData(Buffer[voice], AL_FORMAT_MONO16, buf[voice], len, srate);
alSourcei(openAL.Source[i], AL_LOOPING, AL_TRUE);
alSourcei(Source[i], AL_BUFFER, Buffer[i]);
alSourcePlay(Source[voice]);
}
} else --mtime[voice];
}
}
Well, it turns out there were 3 problems with my code. First, you have to link the built wave buffer to the AL generated buffer "before" you link the buffer to the source:
alBufferData(buffer,AL_FORMAT_MONO16,&wave_sample,sample_lenght * sizeof(short),frequency);
alSourcei(source,AL_BUFFER,buffer);
Also in the above example, I multiplied the sample_length by how many bytes are in each sample (in this case "sizeof(short)".
The final problem was that you need to un-link a buffer from the source before you change the buffer data
alSourcei(source,AL_BUFFER,NULL);
The music would play, but not correctly until I added that line to the note change code.