You can’t really control that. Buttons will always only jump to the next PGC or chapter marker, so you will always see some flashing, should your motion menu not be at the ideal frame (in addition to the slight delay introduced by the jump itself on a hardware level because the optics of the player need to move and read another part of the stream). You should make sure that each preview image goes thru a full cycle and then animate your transition as you need it after this one cycle. This way you can at least adjust the incoming animation in the next menu to be halfway seamless. The transitions themselves need not be anything special, just dumb timelines that are entered from one menu and exit to another menu. As long as you keep your navigation linear, you should have no problems keeping track of your transitions and timelines. Things will however get very bloated and at times confusing, if you add more levels of navigation.
Mylenium
[Pour Myl