[pulseaudio-discuss] Resampler quality evaluation results

[Laurențiu Nicola]

I have a question related to your tests. In my application, I need
resampling between close rates (let's say from 44200 to 44100). Do you
feel that the results would basically be the same in this kind of
situation?

Thanks,
Laurentiu Nicola

On Wed, Sep 3, 2014, at 10:25, Alexander E. Patrakov wrote:
> 25.08.2014 00:53, Alexander E. Patrakov wrote:
> > Unfortunately, there is a bug on win81 plots, because Windows Media
> > Player by default attenuates the file by 6 dB, and my scripts compensate
> > for that, but also amplify the quantization noise. I am too lazy to fix
> > this today. Please shift the whole win81-wmp curve down by 6 dB, and
> > you'll hopefully get an approximately correct result.
> 
> Yesterday's discussion with David Henningson on IRC has led to the 
> discovery of another bug. Namely, all plots are saturated at 18 dB. That 
> was because I mistakenly included the distortions introduced by the 
> resampler into both the signal and the distortion. So the original plot 
> answers the question: how much audible are the distortions similar to 
> the original ones, in the presence of both the original sine wave and 
> the original distortions? As the distortions _also_ mask a copy of 
> themselves, the answer cannot be greater than 18 dB.
> 
> This is now fixed in git, but this also means that I can no longer plot 
> the trivial resampler using the same convenient y scale as others. At 
> very high frequencies (20 kHz), the distortion audibility of that 
> resampler goes up to 80 dB, and that's completely understandable. At 
> such high frequencies, the distortions of this resampler are indeed more 
> powerful than the original signal, and, unlike the original signal, are 
> concentrated in the frequency range that we hear very well, unlike the 
> original signal (which no longer masks anything).
> 
> Results for high- and medium-quality resamplers (i.e. anything better 
> than speex-float-3 below 10 kHz) are not significantly affected by the
> bug.
> 
> -- 
> Alexander E. Patrakov
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