RE: Simple filtering in realtime - again...

Thank you Dan, but I'm afraid that didn't work. I think there's something wrong with de casting, but I'm not very sure what is it, or how to fix it.



Subject: Re: [Openal] Simple filtering in realtime - again...
To: [email protected]; [email protected]
From: [email protected]
Date: Tue, 20 Apr 2010 09:38:40 +0100


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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Fruskus <[email protected]>











Fruskus <[email protected]> 

Sent by: [email protected]
19/04/2010 10:41








To

[email protected]



cc





Subject

[Openal] Simple filtering in realtime - again...











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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