Technical doubts on SAI interface(STM32F7)

I am using STM32F767ZI nucleo board to interface external audio device(ADAU1772) through SAI interface. Here I configured SAI(Master) in TDM mode to receive 4 channel audio signal. I can able to receive the data using Interrupt method. But how do I separate the data of each channel ,Is there any channel indication byte in the frame.

Can you please give some brief detail on this.

>> Also If I tried same in DMA method I am not receiving data continuously , Can you please suggest how to receive data using DMA. And what is the maximum number of byte I can receive without CPU interruption .

Thank you.,

Best Regards.,

Edwin