Merge three gray video streams of same width and height into single video stream:

[a0][a1][a2]mergeplanes=0x001020:yuv444p

Merge 1st yuv444p stream and 2nd gray video stream into yuva444p video stream:

[a0][a1]mergeplanes=0x00010210:yuva444p

Swap Y and A plane in yuva444p stream:

format=yuva444p,mergeplanes=0x03010200:yuva444p

Swap U and V plane in yuv420p stream:

format=yuv420p,mergeplanes=0x000201:yuv420p

Cast a rgb24 clip to yuv444p:

format=rgb24,mergeplanes=0x000102:yuv444p