I am using JRiver MC19.0.57 on a 2009 Mac Mini running OS X 10.6.8. As I play ALAC files (44.1/16), I occasionally experience gaps of about 3 seconds mid-song. I notice them somewhere between once per track and once every other track while playing complete albums. (I'm not talking about gaps between tracks -- I'm talking about short freezes in the middle of tracks.)
My Mini is a dedicated media server, and JRiver is the only software that is running, so I'm doubtful that the gaps are a result of limited CPU resources. The ALAC files themselves are stored on an external drive that is connected to the Mini via FireWire 800 (it is the only FireWire device connected to the Mini). I haven't noticed these gaps when playing back MP3, FLAC, or WAV files, so I suspect that the problem lies in JRiver's handling of ALAC. (That said, the vast majority of my music library is ALAC, and I haven't played a playlist of only MP3, WAV, or FLAC files to test exhaustively whether they lead to gaps during playback.) The Mini is on a wifi network along with other devices that might occasionally generate a lot of network traffic. However, I am experiencing these gaps while the mini is playing music locally, so I doubt the availability of network resources is causing the problem.
Has anyone else noticed this? If it's indeed a bug, can someone advise whether it's been fixed in one of the newer releases of MC19?