You can toggle this informational display by pressing the INFO button on the front panel of the receiver or on the remote control (depending on your model receiver) – you will have three choices: DSP Program, Audio Decoder, and Input. You cannot "turn the decoder on" - the receiver is designed to automatically select and activate (turn on) the proper decoder based on the input signal from the source (DVD player, BD player, cable box, etc.). The front panel display of the receiver reads DECODER OFF. It can mean one of two things - a two channel source is input or there is no input. Well I have seen this a few times on the site, and it was due to the HDMI Inputs being faulty and the Yamaha not receiving a signal, thus giving the "Decoder OFF" message. - Yamaha - United States. In either case the receiver would not need to turn on a decoder to play sound. For example, if your DVD player sends a Dolby Digital signal to the receiver the receiver will see that and automatically activate the Dolby Digital decoder. It can mean one of two things - a two channel source is input or there is no input. In that case, the unit needs to be sent out to Yamaha for them to replace the HDMI Inputs, and check the 5 volt Bus Power coming into the processor. Just one bent or damaged cable or connector can cause a loss in picture and/or sound. What does this mean and how can I change it? The DECODER OFF message is purely an information message. I have a Yamaha RX-V471 receiver that just started displaying a Decoder off message on the receiver display then the display started flashing multiple display functions. In either case the receiver would not need to turn on a decoder to play sound. The DECODER OFF message is purely an information message. If the decoder off message is accompanied by a loss in picture and/or sound, we would suggest double checking all your connecting cables between the source component and receiver. The INFO button basically tells you the status of the receiver.