that all makes sense, I guess. But why did the DTS track show up on the receiver as Dolby Digital when the player was set to Mix Audio Output ? It was my understanding that if it was set to Mix Audio Output and there was no secondary audio, the hd track would be played.^ You did good.
Secondary Audio is a “feature” of the Blu-ray spec. It allows the studios to include a separate Stereo audio track which plays along with your choice of feature audio. It is used for menu sound effects (beep when you click on an on screen button) and SOME Commentary tracks which are typically authored as Picture-in-Picture: See a small window pop up with Commentary video while watching the feature.
MOST Commentary tracks do not use this. They are authored as an entirely separate feature track which plays instead of the normal feature audio and usually includes some feature audio baked in whenever the Commenters shut up.
Only the player knows about Blu-ray Secondary Audio; your AVR or TV has no clue about it. So to hear Secondary Audio you must let the player “mix” the Stereo Secondary Audio track (e.g., button beeps) with whatever normal, feature audio (e.g., menu background music) is already playing. The mixed combo becomes the one and only audio the player sends out.
Now, when the feature audio track is a Bitstream like DTS or DD, that mixing can’t happen until the player first decodes the bitstream audio format into its component, LPCM digital audio streams — one per speaker channel. And if you have told the player to output Bitstream audio the result, AFTER mixing in the Stereo Secondary Audio, has to be re-encoded BACK into a Bitstream for output.
Some players will always produce a DD bitstream when doing the re-encode, even if the original feature audio was DTS.
By enabling audio Mixing, you’ve told the player it is OK to do this!
But it gets worse! If the feature audio is a “lossless” Bitstream track — Dolby TrueHD or DTS-HD MA — the Bitstream created for output after the mixing will be LOSSY DD. And DD 5.1 even if the original track was 7.1. Why? Because no player has the horsepower to create a Lossless Bitstream on the fly like this.
So the Rule of Thumb when using HDMI Bitstream audio output is to turn Secondary Audio Mixing OFF! Only turn it on if you really need to hear Secondary Audio — such as when you’ve selected one of those Picture-in-Picture Commentaries.
So why did DTS work on SOME of your discs? Because not all discs include Secondary Audio. For such discs, mixing can’t ever happen and so the player leaves the original DTS Bitstream unmolested.
But for discs that DO include Secondary Audio — ANYWHERE on the disc — the rules of Blu-ray playback require the processing for mixing to happen EVEN IF you’ve not selected to play a disc feature (such as a Commentary) which actually uses Secondary Audio.
Again: Leave Mixing disabled when using Bitstream audio output except when you decide to play an on-disc extra which requires it.
My player is set up by both digital cable for audio and HDMI. When played through the digital cable, the core DTS or Dolby Digital tracks are played. If played through HDMI, the Dolby TruHD or DTS HD Master Audio tracks are played.
Also, if I want to hear the DTS HD Master Audio, do I bitstream or PCM ?