Bravia Engine is a post-process engine created by Sony for the Sony Ericsonn phone brand. BRAVIA is an acronym of “Best Resolution Audio Visual Integrated Architecture”. You can say the enhancement only on-screen because the engine not changes the input of the screen but it operate on the output.
Sony xLoud Sound Mobile is a sound engine that change the output values of your phone. It includes sound libraries and a software equalizer for the best audio experiance! The best quality is produced in cooperation with Beats Audio! This enhancement can work with the standards htc enhancement! So it can work with beats audio for an exclusive music and movie experience!
*You can read the story of this stuff in this post: HERE (tnx to Bassini)
*You can read explanation on bravia engine in this post: HERE (tnx to ykk_five)