Only transcode high bitrate FLACs?

Hi, I'm brand new to Subsonic and trying to stream my music collection to iOS devices connected to external DACs, and to Chomecast/Chromecast Audio.
My Chromecasts can handle FLACs up to 24 bits / 96 khz.
How do I tell Subsonic to transcode only 24 / 192 kHz FLACS down to 24/96, and leave all other FLACS alone?
In other words I don't want Subsonic to transcode 24/96, 24/88.2, 24/48, 24/44.1, 16/44.1, etc FLACs, only those "higher" than 24/96.
My Chromecasts can handle FLACs up to 24 bits / 96 khz.
How do I tell Subsonic to transcode only 24 / 192 kHz FLACS down to 24/96, and leave all other FLACS alone?
In other words I don't want Subsonic to transcode 24/96, 24/88.2, 24/48, 24/44.1, 16/44.1, etc FLACs, only those "higher" than 24/96.