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LFE Mixing: Question and potential Enhancement

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mattkhan:

--- Quote from: mojave on June 10, 2022, 01:53:29 pm ---ITU BR.1384-1 provides the "Parameters for international exchange of multi-channel sound recordings with or without accompanying picture" which states that "the LFE channel is recorded with a level offset of –10 dB."

--- End quote ---
I can't say I follow such standards (or have lots of multichannel audio content) so I'm curious whether releases are applying this standard consistently, do you know?

mattkhan:

--- Quote from: mojave on June 10, 2022, 01:56:36 pm ---I tried to duplicate using JRiver's Audio Calibration for 7.1 and downmixed to 4.0. It plays fine for me. Did you make sure Subwoofer isn't set to Silent (don't use subwoofer in downmix) in Output Format?

--- End quote ---
thanks and well spotted, I did have that option set.

AGAWA:
https://www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/38_LFE.pdf

mattkhan:
repeated the same test

on the LFE only down to 4.0 -> -12dB down on each channel
on the LFE + L down to 4.0 -> L is 8.386dB down, other channels are -12

it's not immediately obvious to me what JRSS is doing in this case but i can't see how these numbers equate to there being a +10dB boost applied

fwiw in the 2.0 case, the same level difference appears to apply (i.e. L in ~3.7dB higher than R) which suggest some LR only balancing here?

I don't recall the behaviour of JRSS ever being documented so probably you just take it as is or be happy doing it yourself

stewart_pk:

--- Quote from: Hendrik on June 10, 2022, 10:57:05 am ---JRSS downmixing will never result in clipping, if it needs to then the mains will be reduced in volume, but thats an unlikely scenario, as the volume is already being reduced as the data is spread over different channel, and the risk of clipping is reduced as data is not necessarily correlated.

Note that its entirely expected that even the LFE channel will have data close to the maximum the channel can support - the 10dB boost would serve no purpose if it was quieter, why would you not just make it louder in the file afterall.

--- End quote ---

That is good to know that JRSS won't clip, but would it not be played 10dB too loud at typical volumne levels?

I don't understand your point in the second paragraph.
But regardless, I think there are two potential whorthwhile enhancements.
1) Provide a dropdown relative to downmixing with options of "Mix LFE to all channels" and "Mix LFE to the main L and R channels".
2) Provide a checkbox option of "Don't apply 10dB boost to LFE" which if checked would apply to both non-dowmixed and downmixed output.

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