Use a SampleChannel or ToSampleProvider to capture the audio samples using an event/callback function.
In the event/callback function you capture each sample (L and R values) one by one and add them to a List<> or an array with a size of 2048. When the sample count reaches 2048, send the data to the FFT and reset the array back to zero.
In the event/callback function you capture each sample (L and R values) one by one and add them to a List<> or an array with a size of 2048. When the sample count reaches 2048, send the data to the FFT and reset the array back to zero.