This is a strange problem, and I've spent most of the day troubleshooting and trying to confirm exactly what is going in. This is not new, I've suspected it for many months, but did not have time until today to try and troubleshoot exactly what is going on.
Here's the actual problem. I'll follow with the process I've used to try and narrow it down to JRiver Media Center. I've done all my troubleshooting on 30.0.66 and then confirmed it still exists in 30.0.69
Playback from Media Center to my iMac speakers is correct with no issues. I'm running Ventura 13.2.1, my iMac is a 27" 2020 intel model with 32 gigs ram. I am using the Core Audio default under the Audio section of Options in JRiver Media Center and i have nothing configured or checked in the DSP and Output section.
I have a pair of Homepod mini's updated to current version 16.3.2 They are paired together as a stereo pair.
When i change the sound output from iMac speakers to the stereo paired homepods (using the speaker icon on the Menu bar of the iMac) the pitch of any music that is played with JRiver Media Center is lower and the speed is slower. It sounds like someone put a finger on a reel to reel tape and slowed it down. I conducted multiple tests with a track that is 4:50 long. When played on the iMac speakers it plays for 4:50 (i used a stopwatch). When played through thr stereo homepods the same track plays for 5:14. The speed is constant, no fluctuation, just slower and lower in pitch.
I did two more tests to see if the problem was my iMac or JRiver Media Center as follows:
I played the same track (this is a digital ALAC file on my iMac drive, not streaming) through Apple Music to my iMac speakers and also through airplay to the stereo homepods. It plays at the proper speed with no problem both ways.
I then loaded a utility from Rogue Amoeba called Airfoil which allows playing music from my iMac to multiple airplay enabled speakers throughout my home. Playing the same file using JRiver Media Center and the file plays perfectly to the stereo homepods and any other speakers i select using Airfoil.
So the problem is: Playing any of my music files with JRiver Media Center to my stereo homepods results in the music playing verifiably slower and at a lower pitch. Playing with JRiver media center directly to my iMac speakers plays properly. Playing using Apple Music or using JRiver through the Airfoil utility also plays properly.
I have checked and unchecked the DSP box for integer mode and it makes no difference. The exclusive box is unchecked. I've never been able to check that DSP box because it crashes JRiver Media Center so i long ago changed it to unchecked.
I'd appreciate any tips or other options to try.
BYW, i also have a zone set up to play directly from JRiver Media Center to my DAC (a schiit Bifrost) and i have no issues whatever with playback with that zone.