This parameter indicates to a decoder whether the two‐channel encoded bitstream contains a Dolby Surround (Lt/Rt) program that requires Dolby Pro Logic decoding. When downmixing to stereo from a multichannel input, set this value according to the type of downmix performed (Lt/Rt: `ENABLED`, Lo/Ro: `DISABLED`). When transcoding a stereo Dolby Digital, Dolby Digital Plus, or Dolby E input, the value must be passed through from the input bitstream to the output bitstream. When transcoding a third-party stereo input to stereo Dolby Digital set the value to `NOT_INDICATED`.