Maybe gstreamer can do that, when you have two cameras connected to one graphics chip.
My configuration is different:
- I have one arm-board with two different graphics chips, each of which should support one camera
- the cameras already supply de-interlaced streams
- according to freescale documentation the VDI can do combining of two CSI streams _OR_ de-interlacing
- infact, freescale told me, that the actual BSPs do not support this feature and are not intended to support this in the future