enda.bates@gmail.com

Hey everybody, thanks for the help with my float inlet yesterday!

I am now trying to add a circular buffer to my external. The buffer will need to hold something in the order of 2048 samples.

Now Im thinking I need to create this buffer outside the perform routine as this routine only works in chunks of samples as per the Signal Vector size, right? So where do I create the array to store these samples, in the structure defn or in the new instance routine, or where?

As far as I understand it the array/buffer will need to outside the perform routine so it can store samples from previous Signal Vectors. So i guess this needs to be a global variable that can be accessed from the perform routine, but i guess Im not sure where is the best place to do this code in an MSP external.

Hey everybody, thanks for the help with my float inlet yesterday!
I am now trying to add a circular buffer to my external. The buffer will need to hold something in the order of 2048 samples.
Now Im thinking I need to create this buffer outside the perform routine as this routine only works in chunks of samples as per the Signal Vector size, right? So where do I create the array to store these samples, in the structure defn or in the new instance routine, or where?
As far as I understand it the array/buffer will need to outside the perform routine so it can store samples from previous Signal Vectors. So i guess this needs to be a global variable that can be accessed from the perform routine, but i guess Im not sure where is the best place to do this code in an MSP external.
Your help is greatly appreciated,
cheers,
enda


how-to-code-a-circular-buffer-in-an-external

I think you should allocate the mem in your dsp function.

Put a float* into your main object, like so:

#define kNumSamplesInCircularBuffer 2048;

    t_pxobject xObj; // requred for msp

and then malloc a buffer and give it to your object like so:

void MyObjName_dsp(MyObjName* inObj, t_signal **sp, short* count) {

    circularBuffer = (float*)malloc(sizeof(float) * 

    //initialize the read and write index

    //initialize the buffer with zeros

    bzero(circularBuffer, sizeof(float) * kNumSamplesInCircularBuffer);

and then free the buffer when you're done.

    //for paranoia's sake I always zero out my structs after I free any 

then inside of your process function, just make sure you don't access 

typedef struct _MyObjName {
	t_pxobject xObj; // requred for msp
	int curReadIndex;
	int curWriteIndex;

	//allocate the buffer
	circularBuffer = (float*)malloc(sizeof(float) *  
kNumSamplesInCircularBuffer);

	//initialize the read and write index
	curReadIndex = 0;
	curWriteIndex = 0;

	//initialize the buffer with zeros
	bzero(circularBuffer, sizeof(float) * kNumSamplesInCircularBuffer);
}

void MyObjName_free(MyObjName* inObj) {
	dsp_free((t_pxobject*) xObj);

	//for paranoia's sake I always zero out my structs after I free any  
malloc'd members
	bzero(inObj, sizeof(MyObjName));
}

then inside of your process function, just make sure you don't access  
outside of the bounds of your buffer.

How to code a circular buffer in an external.