Function find_matching_consumer_rtx_capability 

fn find_matching_consumer_rtx_capability<'a>(
    format: &MediaFormat,
    negotiated_formats: &[MediaFormat],
    capabilities: &'a MediaCapabilities,
) -> Option<&'a MediaCodecCapability>

Consumer-side RTX matching works against the already-consumable stream. At this point the stream’s apt must refer to a primary PT that survived consumer negotiation, otherwise forwarding RTX would create an orphan repair stream with no valid primary target