Originally Posted by mphil
I sent an email again today too. My Roku is connected the same way as the Oppo, one cable to TV and audio cable to Denon, no problems, Thanks.
There's a subtle, but very important difference there. With the Oppo, I presume you're using 2 HDMI connections (HDMI1 to the display for video, HDMI2 to the AVR for audio), while with the Roku I'll assume you're using HDMI to the display for video and Optical to the AVR for audio (as the Roku only has 1 HDMI output). If you used Optical or Coax digital audio from the Oppo to the AVR for audio, you would most likely find that the issue you're running into is resolved. Of course if you did that, you would lose some audio modes (no SACD audio, no Dolby TrueHD, no DTS HD Master Audio).
I don't use both HDMI outputs and I don't recall exactly what the UDP-203 is supposed to do with the audio for HDMI1 when using both HDMI outputs, but if the Oppo is supposed to mute audio on HDMI1 when it detects that HDMI2 is connected to something, the most likely problem here is that the AVR is keeping the HDMI input active such that the Oppo think's it's still connected even when the AVR is turned off. Of course, disconnecting the HDMI cable ensures that the Oppo enables audio on HDMI1 again.
There may be options in the AVR that you can turn off (such as HDMI preview that can give you thumbnails of what all the HDMI inputs currently have connected) so that the Oppo won't think the port is active when the AVR is either on a different input or turned off.
Another option could be to install a simple HDMI switch between the Oppo and the AVR; switch it to another input to break the connection between the Oppo and the AVR when you want audio on the Oppo's HDMI1 output.
Another option could be to see if Oppo can provide a feature to force audio to be enabled on HDMI1 even when it detects that HDMI2 is connected. This, of course, would require a firmware update in the Oppo.