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41.183.0.21
In Reply to: RE: the dubious pleasures of resampling posted by steppe on May 30, 2009 at 13:21:27
Take a low-res pic which would be our 44.1k. Then take a hi-res pic (@ ~4x) to be our 192k version. Yes the upsampled results are as per the hi-res picture if strict bandlimited interpolation is done (SRC does this; I'm not able to verify SoX but their site suggests so).
At issue with the upsampled hi-res pic would be added artefacts ("ringing" or more correctly "Gibbs phenomenon"). New information is added wherever we go from low to high intensity (i.e. discontinuities). This means at these boundaries the low intensity area now contains information that's NOT visible to us. This would be in the UltraViolet (UV) spectrum. Aside: Radio, TV, Microwave & Infrared are lower down the spectrum to visible light. Beyond UV are harmful X-rays and Gamma-rays.
So does this invisible artefact affect the visual? Experimentation with SoX confirms this to be true. SRC offers no settings but has a redeeming feature in that the pre-ringing (same for post-ringing) is just ~0.3ms in duration. SoX offers settings that reduce the pre-ringing but at the expense of changing some aspects of the visual (phase shift). Although the pre-ringing is short, the levels are relatively high (some 36db lower than transient peak) bringing into question how well your speaker's tweeter can handle this ultra-sonic load. Should this be at or near the break-up or resonance frequency, your tweeter is most likely to loose the plot...
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