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[mojave]

On one of my systems, I typically watch movies down-mixed to stereo. I've been using the volume control for fun on my new MOTU 1248 since it is easy to adjust and I can mute with a push of the button. This means internal volume on JRiver is set to 100%

I was watching Interstellar and it was constantly clipping. The audio had been analyzed and I had Volume Leveling and Peak Level Normalize turned on. Peak Level (R128) is +1.7 dBTP.

I have attached the copy of Audio Path.

Questions:
1.  Volume Leveling lowers volume by -2.7 dB and Peak Level Normal increases volume by +2.9 dB. Why is Peak Level Normalize increasing the volume when there are +1.7 dBTPs and it is being downmixed? I thought Peak Level Normalize took True Peaks into account.

2.  Audio Path shows the volume adjusted -2.7 dB for clip protection. I had to adjust the internal volume by -4.5 dB and clip protection still engaged. I had to go to -5 dB before it didn't engage. Why is clip protection not reducing the volume enough to prevent clipping? I verified that clipping was still happening at -4.5 dB internal volume by also looking at it in Voxengo SPAN VST plugin.

Clip protection doesn't fully take care of the clipping. Either the down-mix should use lower volume, Peak Level Normalize should be smarter, or clipping protection should be more aggressive. The first two are preferred since they don't cause volume adjustments during the movie.

[6233638]

Are you sure the track has been analyzed? Peak Level Normalization is operating in the adaptive mode, rather than the fixed mode.

EDIT: Hmm, I'm seeing this as well. For some reason audio analysis is not being used for Peak Normalization with multichannel audio playback? (not specific to DTS-HD)
It seems to be working with stereo.
 
EDIT2: Oh, of course - if anything in the playlist has not been analyzed (in my case, it was a Blu-ray disc) - even if that is not the file currently being played - it will use adaptive mode.
Removing the non-analyzed files switched it over to fixed mode.
 

At the same time, it is still possible for MC to clip when downmixing as JRSS intentionally does not do full normalization - which is something I'd like to see change - but that's not the issue here.

[Hendrik]

"adaptive" is a sign that it isn't actually using the analyzed information, so something in either your playing now playlist or your library is off.

[mojave]

I made sure Interstellar was the only item in the playlist.

Audio Leveling:  -2.7 dB
Peak Level Normalize (fixed):  +6.3 dB

I had to turn it down -8.0 -8.5 dB to prevent any clipping.

[mojave]

I actually had to adjust it to -8.5 dB to prevent clipping. You can see in the attached picture that clip protection was activating at -8.0 dB. Even though clip protection shows -0.0 dB, I verified with SPAN that the output was over by about 0.3 dB.

[6233638]

It seems like this is Peak Level Normalization not interacting well with downmixing then, even when dealing with analyzed files and operating in the fixed mode.
 
I expect that even with the correct downmix being applied, PLN would still push it to clipping.
 
 
However, if you're actually hearing distortion due to "clipping" rather than a reduction in volume when clipping protection kicks in, I just tested it again and the LFE Channel is still not being low-passed. Despite all that discussion a while back, it doesn't look like the fix (24dB/Octave low-pass at 120Hz) was actually applied.
 
So while clipping protection is being enabled, what you're hearing may actually be due to the LFE channel not being filtered.