DTS-HD MA source resulting in Dolby Digital?

Setup: Latest Infuse (Pro) on Apple TV 4K --HDMI-> Samsung UE65KS8000 TV --HDMI-ARC-> Onkyo TX-SR608 Amp

Samsung TV

  • HDMI Audio Format (input): Bitstream (options are PCM/Bitstream)
  • Audio Format (output - ARC/SPDIF): Dolby Digital (options are PCM/Dolby Digital/DTS/DTS Neo 2:5

Harry Potter #4 .mkv on UNC share with audio #1 track DTS-HD Master Audio.

During playback I get (decent?) 5.1 audio and the Amp displays the Dolby red icon.

I understand (correct me if I’m wrong):

  • Apple TV 4K can’t bitstream DTS-HD MA
  • ARC can’t bitstream DTS-HD MA nor 5.1 PCM (only Dolby Digital and 2.0 stereo PCM?)
  • The red icon means the Amp is receiving a Dolby Digital bitstream through the HDMI ARC

My questions are:

  1. Is this a ‘bad’ setup given the limitations of the hardware products?
  2. What is the Infuse/Apple TV doing with the DTS-HD MA audio track and outputting to the TV? Decoding to PCM?
  3. How/why is the TV encoding (?) this to Dolby Digital? Is PCM → Dolby Digital a thing?
  4. There’s a ‘DTS’ option in the Audio Output menu that’s greyed-out, surely this would be the ‘right’ output for a DTS-HD MA stream?
  5. I’m considering upgrading my Amp and putting that in direct (removing ARC - currently not an option as my Amp doesn’t support 4K). Would this give me (significantly) better audio than today?
  6. What’s “best case” setup for a DTS-HD MA mkv track on ATV unless/until Apple introduce bitstream output? Infuse decode to LPCM 5.1 over HDMI to directly connected Amp for lossless audio?

Thanks in advance.

Don’t use ARC. Bad setup. Run all your boxes directly into your receiver. Only use ARC if you have apps on your tv that require audio.

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Nothing I don’t already know my friend!

I use TV apps currently and my amp doesn’t support 4K passthrough, so I’m stuck with ARC until I upgrade the amp.

I was looking at upgrading my Sonos (gen 1 Connect, no longer supported) and getting an Arc for Dolby Atmos - but that’s an even bigger mess of incompatibility (ATV limitations and Arc not supporting DTS).

So I’m looking to learn the concepts and understand my current setup first.

Well the Apple TV will either output PCM lossless or Dolby digital lossy. If your receiver and TV both support eARC then you can have lossless 5.1 PCM. If they don’t then you’ll be stuck with the AppleTV converting to lossy Dolby digital.

So (2) the Apple TV is converting the DTS-HD MA to Dolby Digital?

Only if you have the output set to Dolby digital. If you have it set to auto then it’ll dump out as PCM.

You’ll need to set your input and output to match on any devices in the chain. Chances are your receiver doesn’t supper eARC so the best you’ll get is 2 channel pcm.

  • I’m getting 6 channel audio from my speakers and the red Dolby icon is lit on my Amp.
  • Neither the TV or Amp supports eARC.
  • Apple TV audio output is set to Auto.

So is this what’s happening?

  • Infuse is decoding DTS-HD MA to 5.1 PCM
  • Apple TV outputting 5.1 PCM to my TV over HDMI
  • My TV is encoding 5.1 PCM as Dolby Digital 5.1
  • and outputting Dolby Digital 5.1 as a bitstream to my Amp over ARC
  • My Amp is decoding and playing 5.1 audio

I’m happy(ish) with the resulting audio, what’s surprising me is if the TV is encoding 5.1 PCM to Dolby Digital - not something I would expect to happen.

But it would help my understanding to know the chain of audio here :slight_smile:

Your TV is doing a reencode to Dolby digital. Regular Dolby digital and regular dts are the only surround sound codecs supported through regular ARC. It’s right there in your settings listed above. You have the output set as “Dolby digital”.

If your setup works then it works…