How to decode 6-track APTX-100 (cinema DTS) with the correct channel levels

[2001CluelessDianogas]

You make a solid argument. But if we assume that an audio processor will treat 5.1 PCM the same way as 5.1 DTS/TrueHD (which would make sense, you wouldn't want your calibration to be off because of some variable like that) then there's still the very convincing matter of the LFE matching blu-rays that more-or-less port the theatrical 5.1 when using the +3/6db rule. The Nolan UHDs are good examples, but I've encountered various others throughout the years. There's also the very subjective argument that I've been listening to tracks that have been editing this way for awhile now and I think they sound right, but take that with a grain of salt.

We could always objectively test weather or not LFE output is the same for bitstream/PCM with an SPL meter. If I can find mine I'll break it out and test.

What is the +3dB or +6dB (or +6dB and +9dB claims) even based on reference to though? Have you been doing manual LFE extraction by low-pass each surround and combining the two channels (using surrounds at given level not -3dB for the LFE extraction)? Or using the auto LFE extraction? Or extracting it from already -3dB lowered surround channels?

I just tested the 3.9 version of the plugin and having it extract the LFE itself as well as auto -3dB each surround.
1. it looks different than manual extraction
2. it comes out too low volume, for pre-1999 JP disc it came out much softer than my manual extraction plus -3dB method. I tried adding +3dB and it was actually still lower volume, +6dB was a touch louder, it seems it's maybe -5dB compared to the "manual method plus a -3dB" so using the auto LFE with version 3.9 I think you'd need to give it a +5dB or for pre-1999 and +8dB or so for 1999+ discs (didn't test whether it comes out this low if you don't select -3dB for surrounds though, perhaps it accidentally just extracts LFE from surrounds after whatever leveling you tell it to give them instead of after)

[2001CluelessDianogas]

You make a solid argument. But if we assume that an audio processor will treat 5.1 PCM the same way as 5.1 DTS/TrueHD (which would make sense, you wouldn't want your calibration to be off because of some variable like that) then there's still the very convincing matter of the LFE matching blu-rays that more-or-less port the theatrical 5.1 when using the +3/6db rule. The Nolan UHDs are good examples, but I've encountered various others throughout the years. There's also the very subjective argument that I've been listening to tracks that have been editing this way for awhile now and I think they sound right, but take that with a grain of salt.

We could always objectively test weather or not LFE output is the same for bitstream/PCM with an SPL meter. If I can find mine I'll break it out and test.

If you follow my instructions for making the LFE you get the same level for LFE for Jurassic Park as the guy in this thread got after making his corrections to the old JP scan's Cinema DTS track where he raised it by +3dB.

To get to the same point manually constructing the LFE I had to do a -3dB to that result to get to the same place.

https://forum.fanres.com/thread-4161.html

The whole you add +3dB or +6dB (or even +6dB and +9dB) talk all depends upon how the LFE was initially created (manually or automatic or by what method of manual) and it's not always clear what the various people were referring to.