[TUniquePtr](API\Runtime\Core\Templates\TUniquePtr)< [ISoundfieldTranscodeStream](API\Runtime\AudioExtensions\ISoundfieldTranscodeStream) > GetTranscoderForChildSubmix ( const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [Audio::FMixerSubmix](API\Runtime\AudioMixer\FMixerSubmix), ESPMode::ThreadSafe > & InChildSubmix )