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LFE Mixing: Question and potential Enhancement

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Hendrik:
If anything this thread shows that the 10dB boost for audio is not very well understood, and options resulting from such a situation are more likely to add to the confusion, rather then solve any problems.
All I see here is theoretical thoughts, no actual data that something is wrong.

From what I understand, properly mastered multichannel audio should always incorporate that boost, in videos or music, this includes DVD-A and Blu-ray Audio, typical sources for multichannel audio, as it serves a real purpose to be able to have the LFE compete with all the other channels in volume, otherwise the LFE would be too quiet.

Downmixing is a special situation as well, and the 10dB boost is handled differently here to account for the fact that its being downmixed. I would recommend to actually listen how it sounds, if the LFE would be 10dB too loud, that would be an easy situation to hear or measure.

AGAWA:
more interesting reading:
https://www.audioholics.com/audio-technologies/0dbfs-blu-ray

mattkhan:
Much of the confusion would disappear if there was a written statement of how JRSS actually (up/down)mixes.

Taking the 7.1 to 4.0 case, I can see that putting the same signal into L and LFE results in the LFE channel being equally distributed across all 4 channels so that the sum of those 4 channels is the same level as the LFE input while the L channel comes out with a signal that is 3.89dB higher in level.

This does not seem to equate to (LFE + 10dB split into 4 equal strength signals) + L as it seems this would result in a signal +5.06dB higher
if there there were no 10dB boost applied then it seems like you'd get a signal about +1.94dB stronger

The actual output is somewhere inbetween the two so the Q is what does it mean exactly when you say the 10dB boost is handled differently here?
In addition, as far as I can see, MC does not apply that 10dB boost at all and expects it to be handled downstream (e.g. by an AV processor).

mattkhan:

--- Quote from: AGAWA on June 11, 2022, 03:41:47 am ---more interesting reading:
https://www.audioholics.com/audio-technologies/0dbfs-blu-ray

--- End quote ---
this is not really relevant to this thread, that is about the fact that consumer equipment generally has problems performing bass management without clipping internally. It's a different thing to how MC up or down mixes.

Hendrik:

--- Quote from: mattkhan on June 11, 2022, 03:46:02 am ---In addition, as far as I can see, MC does not apply that 10dB boost at all and expects it to be handled downstream (e.g. by an AV processor).

--- End quote ---

If you actually output a dedicated LFE channel, then you should control its volume ideally in analog, and not in digital, so you can actually make use of the full range of the signal for all speakers, and don't need to reduce the digital level to allow for the 10dB boost. This is why its not applied in this case, because thats the most reaonable and most expected way to handle it. This is (hopefully) what happens when you let your AV processor or other multi-channel DAC handle it. Active subwoofers typically also have their own volume control to allow you to do this - which you need to calibrate to match your system regardless.

It would not make sense for MC to be the only source to pre-apply the 10dB boost, when every other source won't, and your pre-pro applies it as well, giving you inconsistent results between different sources.

As for technical details on JRSS, we won't detail its exact inner workings, sorry. Down and upmixing is not an exact science, there is some room for interpretation. If you find some real world audio where it doesn't work well, we're happy to listen, but artificial theoretical scenarios just won't get you there.

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