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Re: Quality of CoreAudio SRC
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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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References: 
 >Re: Quality of CoreAudio SRC (From: Brian Willoughby <email@hidden>)
 >Re: Quality of CoreAudio SRC (From: Chris Johnson <email@hidden>)

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