Note: this post is from 2005, outbound links may be broken.
Refined Audiometrics Laboratory PLParEQ1
From the Refined Audiometrics Laboratory website:
You can grab a copy of our PC/VST plugin called PLParEQ1 which is a stereo 1-band ultra-high quality Parametric Equalizer filter.
This is the same technology that we utilize in all of our highest quality systems. This plugin comes with absolutely no restrictions on your use of it, no nag panels, no periodic noise insertions, no dongles — absolutely free.
We want you to experience a taste of our technology. And by giving you the very highest quality in a little tool that you can usefully employ, we think you will be convinced of the quality of our other systems too.
- Internal 88.2/96kHz processing at all system-wide sample-rates
- Runs at 44.1/48/88.2/96kHz external sample rates. (probably many others as well)
- 8-fold temporal overlap processing to minimize audible artifacts of time reversal processing
- Elegant windowing of the data on input and ouput ahead of the 8-way temporal overlap. The window used is w[n] = Sin(Pi/2*Sin(Pi/N*(n+1/2))^2).
- High quality Sinc(x) interpolation utilized in upsampling lower sample-rate data to 88.2/96kHz.
- 64-bit floating point computions throughout, with 80-bit intermediate values during filter computations.
- High performance, highly optimized, scientific-grade code compiled to native Pentium code. Portions may make use of MMX found on Pentium III and older CPU’s.
- Blocking of data is avoided when the system sample rate is already 88.2/96kHz and the filtering is purely causal (i.e., no phase-linear processing).
- Blocking artifacts (IMD) are held below -120 dBFS.
- Quality factor is related to the size of the blocks used during blocked data processing (i.e., during upsampled data or during acausal (phase-linear) processing). Quality factor of 1 corresponds to 512 sample blocks, and quality factor 5 corresponds to 8192 sample blocks, where a block is considered to be composed of data samples at the high internal sample rate of 88.2/96kHz. These blocking factors correspond to throughput delays from 5 to 90 ms, with higher quality processing requiring longer throughput delays.
You can grab your copy, along with supporting documentation at the Refined Audiometrics Laboratory website.