Input buffer structure in an AudioUnit

I've written a simple audiounit that should swap the left and right channels of a stereo source. A ported version of this code worked fine in C for a command-line program that used the BASS library, but I'm having trouble getting the same code to work in Xcode for an audiounit.

For a buffer input of, for example, {1, 2, 3, 4, 5, 6}, i would expect the stereo reversal to be {2, 1, 4, 3, 6, 5}.

My code correctly reverses the samples in this manner, but all I hear is some sort of low-pass filtering, rather than a stereo reversal of samples.

The first 4 values in my input buffer are: 0.000104 0.000101 0.000080 0.000113

The output is: 0.000101 0.000104 0.000113 0.000080

Have I misunderstood something about the way the input/output buffers are structured?

void        First::FirstKernel::Process(    const Float32   *inSourceP,
                                                Float32         *inDestP,
                                                UInt32          inSamplesToProcess,
                                                UInt32          inNumChannels, 
                                                bool            &ioSilence )
{


if (!ioSilence) {                                                 

    const Float32 *sourceP = inSourceP;  
    Float32  *destP = inDestP;  
    for (int i = inSamplesToProcess/2; i>0; --i) { 


        *(destP+1) = *sourceP;
        *destP = *(sourceP+1);

        sourceP = sourceP +2;
        destP = destP +2;
}   
}   
}