Re: Quality of CoreAudio SRC
Re: Quality of CoreAudio SRC
- Subject: Re: Quality of CoreAudio SRC
- From: Brian Willoughby <email@hidden>
- Date: Fri, 1 Feb 2008 14:58:23 -0800
Hi Chris,
You may want to examine the Infinite Wave site. Their graphs of SRC
response covers five different viewpoints: sweep, 1 kHz tone,
passband, transition, and phase. It seems that no single SRC
implementation exceeds in all respects, except perhaps the 64-bit SRC
from iZotope.
What I'm getting at is that the ringing of brickwall filters is
something that can be measured objectively. See their passband and
transition graphs. While you still want to trust your ears, we are
not limited to looking at steepness of the filter alone as a metric
for rating the SRC options available.
I scanned the implementations that were tested by Infinite Wave first
based on sweep performance, and thought I had determined the
"winners." But when I went back and explored the other ways of
looking at the results, I found that it was not so clear any more
which was best. I do not mean to imply that we have reached a point
where we no longer need our ears to evaluate the SRC of choice, but I
will say that the objective analysis tools are improving by leaps and
bounds over what they used to be.
Brian Willoughby
Sound Consulting
On Feb 1, 2008, at 10:30, Chris Johnson wrote:
What I found was, it was extremely tough to do, and the most
effective mode was not the highest quality mode (with the largest
sinc window) but the medium. This is because the highest quality mode
could be driven into artifacts more easily and developed a sort of
'sheen' that could be heard more easily when stressed. I'm trying to
remember who was talking about the audibility of ringing of sharp
brickwall filter implementations but I'm drawing a blank- it's
exactly this that was affecting my ABX tests.
I'd also observe that with the high CD mastering levels of the early
21st century we're actually closer to encountering these pathological
test cases in normal listening, so it's worth paying attention to how
they're handled...
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