Convert yuv422 to RGB

Hi everyone!, i have been searching in the web about a method to transform YUV422 to RGB to can use QImage and use it as a visor to display image (Streaming). Also i have been looking the way that control del pixel informacion getting only "unisigned char * aArray " as a source, i mean how do i control this, how long is a pixel and where the information is (yuv info). YUV pack 4 bites in 2 pixel, how this is translate in offset in the "aArray" .
Well if some one can give a hint on how to manage this i will eternally grateful!
thx!