No. As long as the app
- can decode the original codec
- has the same number of audio channels as the original file
- is allowed to use sufficient bandwidth to stream the original file
it will play the file as-is (i.e. “Direct Play”).
Flac stereo can be played “direct”, both on Android and iOS.
First thing to check is whether the device which is running the Plex client, is able to communicate with your server directly. (Verify the connection is not tagged as “indirect” in the Plex Dashboard).
Then you need to check whether the server is considering the client as being “remote”. Because for remote access, there can be different bandwidth limitations than for “local” connections.
Third is to check the defined bandwidth limitations. Settings on both the server and the client have an influence here.
4th is the cache of the clients. Plexamp in particular has a pre-cache ability, which can buffer several files at once very far in advance. If the client was remote when the file was buffered, the files in the buffer can be in OPUS format.
Even if the device moved into the local network of the server in the meantime, it will still use the pre-buffered file instead of loading the original file driectly from the server.
Plexamp has quite a few preferences to influence these mechanics.
The regular Plex apps for Android and iOS have different (and fewer) relevant preferences.
Most apps (including Plex and Plexamp) on Android and iOS are limited in which sampling rates and word depths they can use. So I’d not expect anything above 48kHz/24bit to play directly anyway.
