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PEQ Bug Causing Clipping (or at least causing JRiver to report Clipping)

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mwillems:
There's an issue with a specific combination of DSP causing clipping when no clipping should occur in this thread:  http://yabb.jriver.com/interact/index.php?topic=99406.msg688449#msg688449

I managed to reproduce it, so it's "real." If you recreate that DSP chain exactly and start playback at 100% of internal volume, most media with a peak at or near 0dB will clip repeatedly, but if you disable the high pass filter at the end of the chain, JRiver will report no clipping or overages.   This is very puzzling as a high pass filter should add no boost and if anything should reduce the total energy present. 

I didn't actually hear any clipping while testing, but that doesn't mean it wasn't clipping.  I'd appreciate it if someone could take a look a this as non-boost DSP should never cause clipping.

Hendrik:
High-pass or low-pass increasing the level at or near the cut off (depending on the algorithm) is not unexpected. Its documented all over the web in various audio forums, people asking about the same things because it caused unexpected problems for them. ;)
Its usually caused by the phase change from the filter.

Some explanation that seemed most logical which I found on a quick look:
https://www.gearslutz.com/board/7793641-post5.html

mwillems:

--- Quote from: Hendrik on August 14, 2015, 01:44:50 pm ---High-pass or low-pass increasing the level at or near the cut off (depending on the algorithm) is not unexpected.

--- End quote ---

But JRiver's filters are butterworths, right? They don't spike like a Chebyechev, they just roll uniformly downwards ("maximally flat magnitude") https://en.wikipedia.org/wiki/Butterworth_filter.  

Or do you mean the total level rises?  Or something else?  I've never seen boosts in level from applying JRiver's crossover filters previously.

Also, the levels in analyzer (including the RMS) don't appear to be clipping, but the clip indicator reports clipping, which is odd.

Hendrik:
You can't see that on a frequency plot like that, but the waveform itself changes shape and can increase in peak. Check the link in my post, I edited it in after.

mwillems:
That makes perfect sense and is kind of fascinating.  I'm surprised I haven't run into the issue before. I wonder how much overhead people should allow for this kind of thing?  Probably 6dB would guarantee it.

It's never bitten me personally because my max volume is set to 90% internal and I use volume leveling.  I'll head back to the thread an report your findings!

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