Subject: Removed a resampler name &quot;anti&quot;

From: shd
Date: Thu Jun 22 16:33:31 2006

To: UADE-Developer-discussion
Removed the name &quot;anti&quot; from resampler list, which meant the accumulator resampler. &quot;default&quot; has meant accumulator for a long time already.

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From: alankila
Date: Thu Jun 22 18:14:05 2006

To: UADE-Developer-discussion
sinc filtering code has also seen an update.

After spending a few months tinkering with different approaches, I posted an update to shd, which is conceptually different and now quite mature.

In this update, I firstly reduce the size of the sinc table from grossly overspecified 4096 point convolution to merely modestly overspecified 2048 point convolution. Sound quality is paramount, and I'm hesitant to reduce the table further without more experiments.

While previously we were talking about FIR convolution, only optimized, the new mode is structured instead like bandlimited step synthesis. The conceptual difference is large, but the implementation is nearly identical to the old.

In band-limited step synthesis, the hard edges of Paula's rising and falling pulses are replaced by values from a bandlimited step table. The exact shape of the blep (which looks like a smoothly rising wave with some ringing on the top) encodes the phase of the pulse which it represents.

The performance of the sinc code has also been improved by combining the digital models of the analog filters directly into the sinc tables. This may seem somewhat miraculous, but it allows running the filters for LED and A500 sound free. Thus when using the sinc mode, filters are evaluated in the Paula's clock frequency of 3.54 MHz, and they have become sampling rate independent. In addition, they replicate their analog counterparts precisely across the audible frequency band.

For filter-less A1200, a low-pass 32 kHz filter has been added to replicate the current leakage into the LED filter.

Also, in order to run IIR filters on the sinc table, the symmetric sinc table has gone through minimum phase reconstruction to give the IIR filters longest period to settle. This should make no audible difference, but explains why there is no longer any preringing at transitions in the sample stream.

The sinc mode does not use floating point computations unlike the default mode, and could be faster for machines without FPU.

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From: shd
Date: Thu Jun 22 18:19:52 2006

To: UADE-Developer-discussion
[quote:0d65591a80="alankila"]After spending a few months tinkering with different approaches, I posted an update to shd, which is conceptually different and now quite mature.
[/quote:0d65591a80]

Things are not mature before they have actually been used by many for a long time. And &quot;default&quot; is still the recommended resampler from my POV.

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From: alankila
Date: Thu Jun 22 20:31:42 2006

To: UADE-Developer-discussion
So, I suppose by that argument sinc is enabled by default in next version of uade, then? I'll call it mature a week after that.