HQPlayer HQPlayer Convolution Questions

[The Computer Audiophile]

Hi Guys, I have questions about how HQP works with convolution filters. @mitchco's Accurate Sound service created my filters and they work perfect in Roon and JRiver. Now when I use them in HQP I don't quite understand what's happening because they don't work the same way. 

 

In Roon and JRiver, I just add the filters, set the volume to max, and call it a day.

 

In HQP there is more going on that I just don't understand and it has an impact on the sound. I believe it's related to limiting and gain, but I'm at a loss. I'll explain it as best I can below.

 

I added the filters via HQP (see below). I don't understand what IR gain means and why it says -8.64216 dB.

 

 

 

When playing music and the volume is set to 0 dBFS, I see the volume "knob" turns red and the Limited counter is incremented each time. I don't know what's really going on here and if this happens with and without convolution filters. 

 

 

 

 

 

When listening with the convolution filters, there can be a serious high frequency cut off. @Miska said this is related to the limiting listed in the HQP interface. I guess I don't understand why this only happens in HQP. 

 

I'm very confused and would love to understand it more so I can write an accurate article on what I'm doing and write a how-to article for others. 

 

Thanks to anyone who can help.

[The Computer Audiophile]

I also need to understand the relationship between the IR Gain that is sensed after loading the filters and the Gain Comp.

 

[The Computer Audiophile]

I'm looking through notes from @Miska and think I may understand the IR Gain and Gain Comp a bit better. 

 

The IR Gain is just an estimator of the boosting done by filters. If I have this correct, then there is a negative gain / boost by my filters that decreases the volume by -8.64216 dB. Is this correct?

 

But, I also have an email from Jussi that says the IR Gain shown is an increase / boost (even though there is a negative in front of the number).

 

I guess I'm lost. 

[The Computer Audiophile]

15 minutes ago, Miska said:

 

This is not related to convolution as such, but it is generic. Most DACs and players just don't tell you about this.

 

If you set volume 0 dBFS and your RedBook content for example is either normalized to 0 dBFS or contains clipping (very typical), you will have inter-sample overs. With just normalized but not clipped you may have +3 dBFS of intersample overs. This is because at for example RedBook sampling rate, the actual sample values don't always happen to be placed at the actual waveform peak, but somewhere else. When simple DAW software normalizes such to 0 dBFS it will cause inter-sample overs in oversampling digital filters that go over 0 dBFS level. Clipped content may make this worse, because then you have essentially square waves in the music where the flat top is at 0 dBFS. When filter (partially) recovers the cut peak, it will again go over 0 dBFS.

 

For this reason you need to leave headroom for such overs, so at least don't exceed the recommended volume setting of -3 dBFS.

 

Many DAC chips and software upsamplers just clip the output at 0 dBFS, while HQPlayer instead applies soft knee limiter to avoid clipping and indicates such event by incrementing the "Limited" counter.

 

Some DACs deal with this the same way, like for example Benchmark DAC3:

https://benchmarkmedia.com/collections/digital-to-analog-audio-converter/products/benchmark-dac3-hgc-digital-to-analog-audio-converter

 

This essentially means that it has internal maximum volume setting of -3.5 dBFS that you can't override. HQPlayer doesn't enforce such on you, but indicates that it is recommended. And HQPlayer's DSP pipeline is 64/80-bit floating point instead of 32-bit integer.

 

I have some material where -3 dBFS setting is not enough, but it is not very frequent.

 

You’re a star Jussi. You’re way ahead of anything I’m thinking in terms of why it works like it does. This is really helpful.