On Sat, Oct 15, 2022 at 10:03:52PM +0200, Åke Nordin wrote: > On 10/14/22 11:21, Alexandre Ratchov wrote: > > Here are the measures of the aliasing noise using sine sweeps. Check > > the figure for the 44.1kHz to 48kH conversion, the sndiod column: > > > > https://arverb.com/pub/src/ > > Those are interesting results, indeed. Is there a write-up about the > testing method somewhere where I can read how to reproduce such tests? >
Sorry, no detailed write-up, but I did the aliasing measurement roughly as follows. Example for 44.1kHz to 48kHz: First generate a sine sweep at 44.1kHz, up to half the sample rate: sox -V -r 44100 -n sweep-44100.aif synth 30 sin 0+22050 gain -6 the gain must be slightly reduced to avoid filter over-shoots which would clip and show the clipping distortion. Then, resample the file to 48kHz using aucat (it uses the same algorithm as sndiod): aucat -n -i sweep-44100.aif -r 48000 -c 0:0 -o sweep-44100-48000.aif And plot the spectrogram: sox sweep-44100-48000.aif -n spectrogram -o sweep-44100-48000.png sxiv sweep-44100-48000.png The column with the "linear" method is obtained by resampling using the old aucat version. The column with the "offline" method is obtained by resampling with sox instead of aucat. Let me know if you need more information or have suggestions.
