Just a heads up, with the new XB1 dash build that just got released to the beta ring, an issue has presented itself.
Instead of being equal space during a letter box feature, it seem as if the content has shifted up.
So instead of equal parts of black top and bottom, its more like 10% black at top 70% move 20% black at the bottom.
I will try and take some pictures later on today to better demonstrate when haven't got the sun glaring all over the screen.
Otherwise playback send normal so far.
Fwiw, Ember and native media player seem to have proportions correct but have grey bars instead of black in the player.