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Author Topic: Parametric EQ  (Read 3774 times)

paul1970

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Parametric EQ
« on: June 18, 2016, 03:25:08 am »

So, I don't understand this:
Running without problems for the longest time and then some video files and multi-channel files play with no Audio...VLC and other things would play them fine. Took me the longest time to track down what the problem was by turning things off and on again one-by-one. I've had some parametric EQ set up for a room hump for ever: r-6db at 51Hz that's MINUS 6. When the affected videos were playing when this EQ was active MC indicated that peak protection was active. It stopped when I disabled the EQ.
Can anyone explain to me what the heck is going on here? Any workarounds/solutions?
Thanks
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Bccc1

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Re: Parametric EQ
« Reply #1 on: June 21, 2016, 04:06:22 am »

There are multiple possible explanations. First, i don't know if MC catches intersample peaks. If not, that would be a good explanation. By attenuating a frequency you could move a peak to a sample that wasn't on a sample but between two samples.
Secondly, by attenuating you can actually increase the peak volume. This is clearly visible when altering a square wave.
Thirdly, I don't know how the EQs are implemented, but some EQs actually boost the frequencys a bit around the cut.
And last but not least, if you have downmixing of multichannel audio and are cutting a frequency before downmixing, you are altering the interference. Maybe there were Peaks that were destructivly interfering and by lowering e.g. 50Hz on the LFE the peak on the Left channel now interferes constructively as the phase was shifted.

To make sure you don't get clipping you could apply a adjust volume on all channels with -2dB. That should cover almost all most cases, as intersample peaks usually are below +1dB. I had very rare cases where I needed to lower the output by 6dB, but I also have some extreme EQing going on, so -2dB should be fine.
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blgentry

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Re: Parametric EQ
« Reply #2 on: June 21, 2016, 06:35:50 am »

Having NO audio is very strange.  This definitely has nothing to do with clipping if you don't hear any sound at all.

My best guess is something to do with your audio hardware and sample rates.  What is your playback device?  How do you have the DSP studio set for 48kHz?  Does it pass through, or do you re-sample it to another rate?

Brian.
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paul1970

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Re: Parametric EQ
« Reply #3 on: June 24, 2016, 01:16:46 pm »

Thanks for the replies. It definitely is clipping because DSP Studio says 'peak' constantly....
I may be resembling 48k to 96k. Can't remember. I will check that and also whether a global attenuate helps. Thanks again.
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RD James

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Re: Parametric EQ
« Reply #4 on: June 24, 2016, 02:19:02 pm »

Are you running 21.0.90? A change was just implemented in that to fix clipping when resampling was active during playback.

There are multiple possible explanations. First, i don't know if MC catches intersample peaks.
It does if your tracks are analyzed and you have either volume leveling or peak level normalization active.
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blgentry

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Re: Parametric EQ
« Reply #5 on: June 24, 2016, 03:00:10 pm »

Clipping does not cause silence.  The OP is describing silence:  No audio at all.

Because it's happening with multi-channel audio files and video, I suspect something with the output format and/or the downstream components.

What do you have the computer plugged in to for audio?

Brian.
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mwillems

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Re: Parametric EQ
« Reply #6 on: June 24, 2016, 03:20:14 pm »

Clipping does not cause silence.  The OP is describing silence:  No audio at all.

Because it's happening with multi-channel audio files and video, I suspect something with the output format and/or the downstream components.

What do you have the computer plugged in to for audio?

Brian.

Technically, clipping can cause silence if it's so extreme it trips MC's "protect" mode which flashes red/yellow down in the clipping detector area and immediately shuts off all sound.  It's MC's way of cutting off audio in an emergency "out of bounds" scenario where the normal clip protection limiter isn't enough.  I've tripped it with a badly designed VST plugin before, and couldn't get any sound from MC without restarting it.  I'm not sure what he meant by "peak protection," but if he meant the emergency "protect" mode he could well get silence.
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blgentry

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Re: Parametric EQ
« Reply #7 on: June 24, 2016, 03:40:06 pm »

^ Ok, I learned something.  "Protect" can be engaged, but the amount of clipping has to be pretty severe. 

I just made it happen by adding 50, 60 or 70 dB of gain.  This was with volume set to 100% and volume leveling/adaptive volume turned off.  That's REALLY heavy gain.

If this is what's happening to the OP he will see Protect in the lower left of the DSP Studio.  Also, if he turns "Clipping protection" to "flatline overflows", he will definitely still get audio.  If it's severely clipped, it will be loud and really, really nasty sounding.  But he'll get audio.

Brian.
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mattkhan

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Re: Parametric EQ
« Reply #8 on: June 24, 2016, 04:50:18 pm »

In case it is not abundantly clear, I would be quite cautious about  how your downstream volume is set before you induce massive clipping just to test something. No magic smoke please!! :)
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