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RE: I'll stick to the technical points then

Posted by Dave_K on November 8, 2016 at 12:30:14:
I read through Stuart & Craven's AES paper a couple times and don't see anything like that.

The closest I can find is a claim in the text that "the end-to-end response, shown in Figure 15, introduces considerably less blur than transmission at 96 kHz using conventional filters, as shown in Figure 14 below." The term "blur" is not defined. Figures 14 and 15 are showing impulse responses. My guess is that the authors are trying to imply that a longer impulse response = more temporal blur. If so, it's disingenuous. A sinc for example, has an infinite impulse response and introduces zero time dispersion and provides the sharpest transient response possible within a given bandwidth.

The closer you get to a perfect brick wall response, the less time dispersion. The more gentle the filter slope, the more it blunts and smooths over transients, and that's what I would call blur. The fact that their proposed response is a Gaussian, which is a filter type normally used for image blurring, makes them sound silly when they talk about de-blurring. It's like they have the whole idea backwards.

The traditional complaint about brick wall filters in digital audio is based on experience with the 44.1k sampling rate. At that sample rate, the signal content coming off the mic feed usually extends above fs/2 , and therefore there is an interaction between the signal and the anti-aliasing and reconstruction filters. Also the filters are operating around the top of the human hearing range. If you just double the sample rate to 88.2k or better, the filters are operating far away from the human hearing range and in most cases, above the input signal bandwidth too. A brick wall filter at 42-44 will pass the signal with no time dispersion and no ringing. Stuart & Craven's filter will roll it off and smear the transients a little bit.