The "Auto Low Latency Mode" (ALLM) is a new HDMI feature defined in HDMI 2.1 that allows a source (e.g. an gaming console such as the XBox One S or XBox One X) to direct all compatible components in the HDMI chain (e.g. AV-Receiver and TV sets) to enter its low-latency mode automatically without requiring the user to navigate a menu to set the optimal latency for their content. This allows the picture to be displayed with least possible delay which is espcially important for gaming.
Sources using ALLM are providing high-quality video data that should require little to no video processing.
Displays using ALLM should reduce this processing (motion compensation, etc.) to minimize delays before presenting the information, making the gaming experience feel more responsive.
Compatible Denon AVRs disable the following functions as same as Game mode in the conventional video mode setting when the ALLM mode is enable at HDMI input signal to achieve a lower latency:
Picture Adjust
i/p-Scaler
Audio Delay (Auto Lip Sync)
ALLM can also solve some video conferencing (Skype, etc.) issues, such as lip-sync.
The ALLM feature is added to all HDCP 2.2 compatible models of Denon AVRs (except AVR-X520BT, AVR-X540BT, AVR-X250BT, AVR-X550BT) and to HEOS AVR, HEOS Bar and HEOS HomeCinema HS2 by firmware update in August / September 2018.
https://denon-uk.custhelp.com/app/answers/detail/a_id/6720/kw/allm