I'm using the BDP-103. I checked the files again with MP3tag and all looked good, I clicked on save again just to be sure. The cover is imbedded in the file on all tracks and so should always show up when the file is played. The cover image is in the same folder labelled as folder and so should show up even if not imbedded in the file itself. I haven't noticed this problem with any PCM file.What oppo model are you using @par4ken?
I can get all my dsf files to show the album jpgs if they are labeled "folder.jpg" but also check those that are stubborn in Mp3tag that you properly associate the folder.jpg file by having the files highlighted and then remember to "save" when all the songs are highlighted. That usually does it for me (205 model) but if not, then I don't know or maybe something happens during the ripping process?
Also, I believe the oppo doesn't mix down the songs in 5.1 but just strips out the other channels; but yes please check that out
The player is supposed to mix the channels down (set under settings) if say you don't have all the speakers, centre and or surround connected. Likewise the back speakers in 7.1 are supposed to be mixed down to the side speakers for 5.1 playback. One peculiarity that I found is if you say that you have back speakers but not side you won't get any output from the back outputs while playing 5.1; you have to say that you have side speakers instead. Because of all this craziness I'm still thinking of building a mixer to take all the outputs and to combine them myself as I see fit!
Is there a difference with dsd vs pcm regarding mixdown? Is there a test SACD available with channel identification signals? That would be the best way to determine what the player is doing regarding mixdown. One could rip the disc and see what happens with the dsf files as well.