This feature will be present in the MIUI version stable. However, this feature can already try with install MIUI version according to the developer, who quoted from XDA Developers.
Mere information, LDAC is the audio codec that Sony developed without compression to a Bluetooth device. This feature is indeed released simultaneously with the presence of Oreo's Android.
This feature offers a Bluetooth-based audio quality is better than ever. Because this feature is capable of sending audio data with 990kbps bitrate.
LDAC alone is usually used for lossless music streaming services or of high quality. A premium-class device is usually used, this feature certainly offers more value to smartphone Xiaomi.