I placed the same question with Oppo and I got a definite answer.
Here you go.
From: OPPO Service <service@oppodigital.com>
Subject: RE: Oppo DV-980H USB and CD
Date: Tuesday, March 31, 2009, 12:55 PM
You can't playback audio and picture files from separate content sources. So if you want to listen to music while looking at pictures, you will need to have the audio and image files on the same USB device or CD/DVD.
To: OPPO Service
Subject: RE: Oppo DV-980H USB and CD
Hi,
So, if I have a mp3 file and pictures (jpeg) on the same USB, I should be able to play them both at the same time?
If so, do I need to do anything special?
Btw, I can't wait for the new Oppo Blu-Ray player.
Thank you for your help.
From: OPPO Service <service@oppodigital.com>
Subject: RE: Oppo DV-980H USB and CD
That is correct. If you load a MP3 file and then an image, you will get a slide show which has audio soundtrack.