Function mxr_select_source_addr 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn mxr_select_source_addr(
    remote: *const mxr_remote_t,
    sink: mxr_bay_uid_t,
    route: *const mxr_v2ip_route_t,
    format: *const mxr_audio_format_t,
) -> mxr_result_t

Routes a V2IP sink’s video, audio and ancillary streams to multicast groups the caller names.

This is the only way to reach a stream no device on the mesh advertises, such as one the calling program is transmitting itself; the routes by source port and by name can only name a stream some bay has announced.

Set all three groups. The firmware decides whether a sink has a manual route by looking at the video and ancillary groups, so a route that leaves either unset does not register as one and the sink falls back to the audio source its mesh picks.

A null format sends 48kHz stereo rather than omitting the field. The firmware stores whatever the frame carries and hands it to the FPGA unexamined, so a frame without a format leaves a zero sample rate there, which the FPGA rejects and which takes the switch down with it.

Safety

remote is null or a live handle, route points at an initialised mxr_v2ip_route_t whose addresses are null or NUL-terminated strings, and format is null or points at an initialised mxr_audio_format_t.