[Georg]

I have an old system without HDMI. PC to pre-pro is via optical (Toslink). With DTS-HD MA I could uncheck the DTS "sub-track" in makeMKV and play the mkv file getting the DTS core via optical. With TrueHD this was not possible. I had to check the "sub-track" as TrueHD did not incorporate a DD "sub-track". I assumed makeMKV presented the separate DD track as a TrueHD sub-track. At some point I discovered that I was getting a DD bitstream via optical even if I left the DD sub-track unchecked.

If I am correct this only applies only to normal TrueHD tracks. Atmos tracks are not bitstreamed as DD.

So, if TrueHD does not incorporate a DD core, how does Kodi bitstream a DD track?
Why is that not so with Atmos TrueHD tracks?

[jjd-uk]

SPDIF is not capable of carrying any type of TrueHD or Atmos track, it will only ever handle Dolby Digital.

If a file has a TrueHD audio track, then with the right settings Kodi will decode it to LPCM and then re-encode it to Dolby Digital, this process is known as transcoding and there's an option for this in the settings.