More > JRiver Media Center 29 for Windows
LFE Mixing: Question and potential Enhancement
stewart_pk:
--- Quote from: mattkhan on June 10, 2022, 06:29:57 am ---The reference level comment refers to films which are encoded in a standard way. Music has, to my knowledge, no such standard.
--- End quote ---
This is exactly what I understand to be the case too, thank you.
At the moment I think JRSS is always boosting the LFE by 10db on downmixing and this could be dangerous with Audio only content (music) and the reason why I started this topic.
I was listening to DVD Audio the other day downmixed by JRSS to 4.0 including the LFE (.1) and the bass did seem too loud.
At the moment I handle this with two zones, one for VIDEO and one for AUDIO with more than 2 channels.
For both, I have JRSS downmix to 5.1 with the option of the center channel moved to the left and right and then manually mix the LFE (.1) channel into the L and R channels. For VIDEO audio I apply the 10dB LFE (.1) boost but for AUDIO only content with more than 2 channels I do not.
Hendrik:
--- Quote from: stewart_pk on June 10, 2022, 09:11:33 am ---The LFE channel and .1 are the same thing.
I have numerous DVD-Audio discs and when I inspect the content in Audacity there is plenty of content on the LFE (.1) channel and not one of my DVD-Audio discs is the 1812 overture.
And two DVD-Audio discs I recently looked at had content peaking about 5dB below full scale.
I think this means that if they were boosted by 10dB by JRSS then they could end up being digitally clipped and hazardous and not to mention just too loud and hazardous.
--- End quote ---
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.
mattkhan:
--- Quote from: stewart_pk on June 10, 2022, 09:18:36 am ---At the moment I think JRSS is always boosting the LFE by 10db on downmixing and this could be dangerous with Audio only content (music) and the reason why I started this topic.
I was listening to DVD Audio the other day downmixed by JRSS to 4.0 including the LFE (.1) and the bass did seem too loud.
--- End quote ---
FWIW I played a 7.1 track that has silence on all channels except the LFE channel, mixed down to 4.0 in JRSS and looked at the resulting output. All channels were silent. It says the LFE channel is discarded when mixing down to 4.0.
mojave:
--- Quote from: mattkhan on June 10, 2022, 06:29:57 am ---The reference level comment refers to films which are encoded in a standard way. Music has, to my knowledge, no such standard.
--- End quote ---
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." DTS and DD also required the same level offset, even if used for just music.
There were a few multi-channel audio recordings on DVD-Audio/HD DVD and maybe some SACD's that had the level too low on the LFE channel. Also, some SACD players played back the LFE incorrect, but that isn't relevant here.
mojave:
--- Quote from: mattkhan on June 10, 2022, 11:05:35 am ---FWIW I played a 7.1 track that has silence on all channels except the LFE channel, mixed down to 4.0 in JRSS and looked at the resulting output. All channels were silent. It says the LFE channel is discarded when mixing down to 4.0.
--- End quote ---
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?
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