How an innocent little audio setting can ruin your day

I'm posting this so that others who go Sony Blu-Ray can solve this problem without as much hair pulling as I went through.

Situation in a nutshell: Got a Blu-ray DVD player to replace an old DVD player on its last legs. Hooked up the same way as old player, but for some reason, movies playing are not being decoded by AV receiver as Dolby D as before. Checked connections, swapped inputs on receiver, nothing worked.

Turns out that by default, the Blu-ray player is set to treat the HDMI output as the primary sound output. Now, ordinarily, I might have ignored that setting, because I was getting sound, just not properly decoded sound. But as it turns out, switching the Audio Output Priority setting to Optical/Coaxial did the trick.