TDA2: data flow of cascade_radar_object_detect

Part Number:TDA2

Hi, 

I am about to use TDA2 to collect and process cascaded 1243 data. I downloaded and installed the PROCESSOR_SDK_RADAR_03_04_00_00 package. 

For C:\ti\PROCESSOR_SDK_RADAR_03_04_00_00\vision_sdk\apps\src\rtos\radar\src\usecases\cascade_radar_object_detect this demo, I see the datapath is shown in the figure below: 

I am wondering if the Select step is to select data from different 1243 radar(Q0,Q1,Q2,Q3) and what is the order of merging the data after fft? And if possible, where could I find the source code doing this step?

Thanks.