Re: Simple filtering in realtime - again...

I think this line is wrong ...

entport[i]=float((Buffer[2*i])/32768);

because you are doing an integer division and then casting the result to a
float.  It should be something like ...

entport[i]=Buffer[2*i]/32768.0f;

Dan
Creative Labs (UK) Ltd.

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                                       [Openal] Simple filtering in        
                                       realtime - again...                 
             19/04/2010 10:41                                              
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Hi,

I keep working on my realtime app.
I've been trying to find the cause of the troubles I had, but I'm still
stuck.

I'm testing now a simple DC blocking filter (just a high pass filter); it
seems to work in terms of frequency, but it adds a very loud constant
noise.
Here's a piece of the code - the rest of the main code is the
capture-playback routine with queue-  :

...

alcCaptureSamples(pCaptureDevice, Buffer,BUFFERSIZE / lBlockAlignment);


// This part is for separating left-right channels
int i;
for(i=0;i<BUFFERSIZE/2;i++){
   entport[i]=float((Buffer[2*i])/32768);		 // entport: input signal
 - left
channel
   //right channel not needed right now
}


DCfilter(entport,portnodc,BUFFERSIZE/2); // portnodc: input signal no dc



for(i=0;i<BUFFERSIZE/2;i++){
		 BufferSalida[i]=ALshort(32767*portnodc.y[i]); // BufferSalida:
Output
buffer
}


// Attaching data to buffer
alBufferData(BufferID[ulQueueCount], PlayFormat, BufferSalida,
BUFFERSIZE/2,
lFrequency);

...

----------------------------------------

void DCfilter(samplesvector &x, nodctype &y, int size){

		 int i;

		 float a=0.995;
		 for (i=0;i<size;i++){

		 		 y.y[i]=x[i]-(y.xdcant)+(a*y.ydcant); //xdcant,
ydcant: previous signal
values.
		 		 y.xdcant=x[i];
		 		 y.ydcant=y.y[i];
		 }
}
----------------------------------------

where:
typedef float samplesvector[BUFFERSIZE/2];

typedef struct {
		 		 samplesvector y;
		 		 float xdcant;
		 		 float ydcant;
		 		 }nodctype;

----------------------------------------

I'm a little bit overwhelmed about not being able to make this work, so,
any
help will be appreciated.
Any ideas?

Thanks in advance.
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