OpenAL alSourceUnqueueBuffers & alSourceUnqueueBuffers - iphone

Question

everyone , I have a problem about the API-- alSourceUnqueueBuffers when I use the OpenAL Libaray.
My problem as follows:
1.I play a pcm-music though streaming mechanism.
2.The application can queue up one or multiple buffer names using alSourceQueueBuffers.
when a buffer has been processed. I want to fill new audio data in my function: getSourceState . but when I use the API of OpenAL alSourceUnqueueBuffers. it returns an error
--- AL_INVALID_OPERATION . I do this as the document about the OpenAL.
so I test a way to solve this problem. I use alSourceStop(source) before the api alSourceUnqueueBuffers, an use alSourcePlay(source) after i filled new data though
alBufferData & alSourceQueueBuffers. but it is bad. because It breaks down the music.
who can help me to find this problem ?
and where i can find more information and method about openAL?
I am waiting for your help . thanks , everyone.
so my code as follows:
.h:
#interface myPlayback : NSObject
{
ALuint source;
ALuint * buffers;
ALCcontext* context;
ALCdevice* device;
unsigned long long offset;
ALenum m_format;
ALsizei m_freq;
void* data;
}
#end
.m
- (void)initOpenAL
{
ALenum error;
// Create a new OpenAL Device
// Pass NULL to specify the system’s default output device
device = alcOpenDevice(NULL);
if (device != NULL)
{
// Create a new OpenAL Context
// The new context will render to the OpenAL Device just created
context = alcCreateContext(device, 0);
if (context != NULL)
{
// Make the new context the Current OpenAL Context
alcMakeContextCurrent(context);
// Create some OpenAL Buffer Objects
buffers = (ALuint*)malloc(sizeof(ALuint) * 5);
alGenBuffers(5, buffers);
if((error = alGetError()) != AL_NO_ERROR) {
NSLog(#"Error Generating Buffers: %x", error);
exit(1);
}
// Create some OpenAL Source Objects
alGenSources(1, &source);
if(alGetError() != AL_NO_ERROR)
{
NSLog(#"Error generating sources! %x\n", error);
exit(1);
}
}
}
// clear any errors
alGetError();
[self initBuffer];
[self initSource];
}
- (void) initBuffer
{
ALenum error = AL_NO_ERROR;
ALenum format;
ALsizei size;
ALsizei freq;
NSBundle* bundle = [NSBundle mainBundle];
// get some audio data from a wave file
CFURLRef fileURL = (CFURLRef)[[NSURL fileURLWithPath:[bundle pathForResource:#"4" ofType:#"caf"]] retain];
if (fileURL)
{
data = MyGetOpenALAudioData(fileURL, &size, &format, &freq);
CFRelease(fileURL);
m_freq = freq;
m_format = format;
if((error = alGetError()) != AL_NO_ERROR) {
NSLog(#"error loading sound: %x\n", error);
exit(1);
}
alBufferData(buffers[0], format, data, READ_SIZE , freq);
offset += READ_SIZE;
alBufferData(buffers[1], format, data + offset, READ_SIZE, freq);
offset += READ_SIZE;
alBufferData(buffers[2], format, data + offset, READ_SIZE, freq);
offset += READ_SIZE;
alBufferData(buffers[3], format, data + offset, READ_SIZE, freq);
offset += READ_SIZE;
alBufferData(buffers[4], format, data + offset, READ_SIZE, freq);
offset += READ_SIZE;
if((error = alGetError()) != AL_NO_ERROR) {
NSLog(#"error attaching audio to buffer: %x\n", error);
}
}
else
NSLog(#"Could not find file!\n");
}
- (void) initSource
{
ALenum error = AL_NO_ERROR;
alGetError(); // Clear the error
// Turn Looping ON
alSourcei(source, AL_LOOPING, AL_TRUE);
// Set Source Position
float sourcePosAL[] = {sourcePos.x, kDefaultDistance, sourcePos.y};
alSourcefv(source, AL_POSITION, sourcePosAL);
// Set Source Reference Distance
alSourcef(source, AL_REFERENCE_DISTANCE, 50.0f);
alSourceQueueBuffers(source, 5, buffers);
if((error = alGetError()) != AL_NO_ERROR) {
NSLog(#"Error attaching buffer to source: %x\n", error);
exit(1);
}
}
- (void)startSound
{
ALenum error;
NSLog(#"Start!\n");
// Begin playing our source file
alSourcePlay(source);
if((error = alGetError()) != AL_NO_ERROR) {
NSLog(#"error starting source: %x\n", error);
} else {
// Mark our state as playing (the view looks at this)
self.isPlaying = YES;
}
while (1) {
[self getSourceState];
}
}
-(void)getSourceState
{
int queued;
int processed;
int state;
alGetSourcei(source, AL_BUFFERS_QUEUED, &queued);
alGetSourcei(source, AL_BUFFERS_PROCESSED, &processed);
alGetSourcei(source, AL_SOURCE_STATE, &state);
NSLog(#"%d", queued);
NSLog(#"%d", processed);
NSLog(#"===================================");
while (processed > 0) {
for (int i = 0; i < processed; ++i) {
ALuint buf;
alGetError();
// alSourceStop(source);
ALenum y = alGetError();
NSLog(#"%d", y);
alSourceUnqueueBuffers(source, 1, &buf);
ALenum i = alGetError();
NSLog(#"%d", i);
processed --;
alBufferData(buf, m_format, data + offset, READ_SIZE, m_freq);
ALenum j = alGetError();
NSLog(#"%d", j);
alSourceQueueBuffers(source, 1, &buf);
ALenum k = alGetError();
NSLog(#"%d", k);
offset += READ_SIZE;
// alSourcePlay(source);
}
}
// [self getSourceState];
}

Answer 1

I found the reason about the problem.
the reason I turn Looping ON : alSourcei(source, AL_LOOPING, AL_TRUE);
if you set this , when the source processed a buffer, you want to fill new data or delete the buffer from the source. you will get the error.