I'm new to BDA driver. Can someone tell to me that if BDA driver need to demultiplex the stream ?

Many tanks.

The BDA drivers relate more to the interface methods employed to control the digital capture device. You can still use custom drivers but your restricted to the application they are made for. Using BDA drivers lets you use a broader range of applications to ustilise a BDA device because of a standard interface. Demuxing of the streams are then achieved in down stream Demux filters.