From your user manual:Here is our Oppo 105D Setup Menu interface and the setup options that clearly pertain to audio...
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This is pertinent if you are using an HDMI connection
Bitstream = raw data output, your AVR decodes the raw DTS or Dolby audio bitstream. None of your other Oppo setting will affect it.
LPCM = decoded output, your Oppo decodes the bitstream before sending to the AVR. Other Oppo settings can affect it.
Yours is set to 'Auto'. I have no idea whether it's outputting Bitstream or PCM.
This is pertinent if you are using coax/optical connection:
Yours is set to 192k LPCM, which means it is decoding Dolby and DTS audio to PCM (think "wav" audio) before sending it to the AVR. It is also downmixing all DTS and AC3 surround to 2-channel, because this connection cannot pass more than 2 channels of PCM audio. It is also possibly resampling the decoded DTS/AC3 audio to 192 kHz, though I might be misinterpreting this, it claims not to upsample anything. If it is not resampling,. the decoded DTS/AC3 audio PCM format should be 48 kHz/24 bit . Other Oppo settings can affect the output as well.