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by nothingtosay at 1:25 PM EDT on April 27, 2013
I'd surely give it a shot, as you likely expect.
by CyberBotX at 3:14 AM EDT on April 28, 2013
OK, I have a version up here: It contains the sinc function windowed to 16 different windowing functions (all of them from that Wikipedia page I linked earlier). Rectangular is pretty much just a straight sinc curve, Lanczos is what is currently in the official plugin. As far as I can see from graphing the sinc curves for each of these windows, most of them will probably sound similar but have subtle differences in them. Let me know which one(s) you like the best.
by Sir-Sabin at 4:13 PM EDT on April 28, 2013
nothing for foobar yet?
by dissident93 at 4:17 PM EDT on April 28, 2013

by JFD62780 at 8:36 PM EDT on April 28, 2013
Okay... I tried the experimental plugin, and I only have one complaint: Is it optimized?

I've been using the Mega Man ZX games as a benchmark, seeing as they had the majority of those stubborn samples I mentioned not too long ago. When I came to the following tracks:

Doomsday Device (MMZX)
Black Burn (MMZX)

The plugin stuttered slightly, and one of the cores of my Pentium D was in FULL USE. (50% overall CPU usage) That was using 96KHz playback, BTW. All 16 methods suffered from said slowdown, EVEN Lanczos, and it never slowed down in the regular plugin!

Anyways, I spotted two methods also suffering from aliasing, namely Rectangular and Poisson. So, I guess, feel free to eliminate those two. Or not, it's your call. ;)
by CyberBotX at 9:24 PM EDT on April 28, 2013
I'm not planning on implementing all 16 methods, maybe just 1 or 2 of them, depending on what others say, unless others really want more than 2 sinc methods for some reason. Plus the experimental plugin might not be as optimized since it is made in a way to allow all 16 sinc methods to share code which could cause a slight bottleneck (since it has to calculate which interpolation was chosen every single time it goes to interpolate, which can be costly I suppose, but I wasn't worried because it was a test plugin), plus it uses a lot of memory for holding the lookup tables in memory. Tha overhead won't exist in the real plugin because it will only need to hold 1 or 2 sinc lookup table(s).

As for the aliasing problem, I've tried looking up what would need to be done for that, and I admit to being a bit mindboggled in regards to the solutions. A lot of them mention things like low-pass filters or anti-alias filters, but I couldn't find anything on how to implement that, and I also want to keep things simple. As far as I can tell, supposedly a proper sinc curve handles anti-aliasing already, but I'm not 100% sure on that either. As you mentioned, the Rectangular and Poisson windows do not seem to help with anti-aliasing.
by JFD62780 at 11:56 PM EDT on April 28, 2013
Just be glad it's only two out of the 16 that are the culprit. ;)

Also, help might come my way in the form of a processor upgrade... I just hope Winamp and/or XMplay's plugin system can properly utilize hyper-threading...
by CyberBotX at 1:32 AM EDT on April 29, 2013
Oh, and just to help visualize things, I updated the Interpolation Comparison page again, I removed the previous plots of the Blackman-Harris and Lanczos interpolations, and show all 16 of the windowed sinc interpolations. It does seem to show really well why the Rectangular and Poisson windows don't sound right. Their plots just look off compared to all the other windowing functions.
by CyberBotX at 5:02 PM EDT on April 30, 2013
I'm still gonna wait to see if anyone else has input on those windowed sinc interpolations, but as it stands, JFD has said only Rectangular and Poisson don't cut for him (due to aliasing), kode54 has told me that Blackman-Harris also produces aliasing, and soneek says that Hann-Poisson, Lanczos, and Blackman sound great to him. That probably means I might use all 3 of those in the final version of this, but we'll see. I think I'd rather just limit it to 1 or 2 of them. If I do, I believe I'd keep Hann-Poisson from soneek's list, and if I do 2 of them I'd also keep Blackman. I wouldn't keep Lanczos if only because it has a lower noise equivalent bandwidth compared to the other 2 mentioned.

As an aside, I have put the NCSF/SDAT tools onto GitHub. I am going to wait until I put out another update to in_ncsf before I put that on GitHub as well, mainly because I need to refactor the directory structure before I upload it to there.
by nothingtosay at 7:09 PM EDT on May 1, 2013
Okay, I did a tournament-style comparison of all 16 and my result is that 12 of them are virtually identical. Some are closer to each other than others, but never to an audible degree to me, with my speakers turned up to a decent level. The only ones that were clearly inferior were Rectangular and Poisson, with strong aliasing, and Welch and Hann-Poisson, with slighter aliasing mainly noticeable from not being present in the others. I haven't experienced audible aliasing from Blackman-Harris with the two tracks I've demoed, but of course, that is only two tracks (I don't have forever and this is time-consuming!).

My opinion is that if you picked at random any of the others to keep you'd be fine.

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