Defined in carb/audio/IAudioData.h

constexpr OpusEncoderFlags carb::audio::fOpusEncoderFlagDiscontinuousTransmission = 0x00000004

This enables a mode in the encoder where silence will only produce one frame every 400ms.

This is intended for applications such as voice chat that will continuously send audio, but long periods of silence will be produced. This is often referred to as DTX.