I used a better grade of pine board, 3/4 inch thick, and cut it to the shape and size I wanted. To attach the shelf to a wall that did not have any backing, I used two more pieces of pine. One extended from the corner to the end of the wall and provided the backing. The other piece provided a horizontal connection where the hinges would go. You can see from the photos below that I used a drop-down hinge in the center, and this has worked really well.
The cords for running power and connecting audio and video between the dvd player and the television are simply run through a plastic white "chase" with an inside elbow attached at the shelf level.