It sounds like you have at least one function for this player under the 0784 code. This is a good place to start. Have you tried any of the other buttons under that setup code? It is ALWAYS good practice to try more than just the power button when looking for a device code.
Transport keys usually are a good place to try with DVD players and VCRs, and number keys with TV and AUD devices. Try reloading 0784 and try out all of the buttons with a DVD in.
If some of them work, you may be able to gain more function with advanced codes (but I am not sure; some combo codes can not accept advanced codes). Doesn't hurt to try!
Jim