Apodizing, anyone?

Does anyone know what an apodizing filter actually does?

I’ve been axperimenting with the filter options on my Mytek Brooklyn Bridge. The one I like best is named “APDZ,” which Mytek describes as an apodizing, fast roll-off linear phase filter. Just wondering what it’s doing.

Thanks.

Thank you. Interesting. He refers to his new apodizing filter as minimum phase, but Mytek describes its filter as apodizing but linear phase. Which in a way sounds like the best of both worlds.

There is quite a bit of discussion and measurements of many of the mytek filters in this review.

Thanks, Phil.

I know how it sounds…like crap

Mytek is most likely using the default Sabre filters. One of which is the linear phase apodizing.

The filters were originally designed by Sabre engineers using the Resonessence Labs DACs as test beds.

Personally with well recorded music linear fast is the best option. If you have some harshness the linear slow might take the edge off and is usually a good match for the Sabre DAC.

.02

Apodizing filters apply a weighting window to the filter coefficients. Depending on the design, they can cause anywhere from a very small to a large loss of resolution. They also compress the transient energy into a broader but smaller amplitude peak.

You can easily hear this effect by comparing MQA vs non-MQA music files. MQA uses an apodizing filter. It is like a very small dose of compression. The net result is the music will sound perceptively louder because the dynamic range will be reduced and the peaks will be closer to the average.

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Thanks, Jeff. Thanks, Jeremy.

What I notice most about the Mytek APDZ filter is an almost crystalline brightness with maybe a little added reverb. I don’t know what’s wrong with me, but I actually like it.

Somewhat related, does anyone here know what the Apod counter in HQPlayer actually counts? I think Jussi said something about bad recordings or bad converters, but what kind of badness is it that is being counted?

Yes, it seems “apodizing” strictly means applying a time-domain window to a filter. I think the general purpose is to reduce ringing in the impulse response, regardless if windowing is used or not during design. Slow roll-off filters do that, but they are “leaky”, so I don’t think they’re a good choice. Using a fast roll-off (“brickwall”) minimum phase filter instead eliminates all pre-ringing, so that may be a better choice. I don’t think ringing caused by brick-wall filters that preserve the full audio range is an issue though, so I always use fast roll-off linear phase if given a choice. That produces the most accurate interpolation.

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