I have downloaded the test files from https://src.infinitewave.ca/faq.html to compare a few apps and settings not in the https://src.infinitewave.ca database yet.
Apart from the finding that Apple's afconvert command line yields some of the best results for free, I was a bit confused of how AP handles the conversion:
- There's Sound > Characteristics… which opens the Sampling Rate/Depth sheet. All fine and good, nearly perfect, almost as good as afconvert or the Izotope SRC that used to be bundled with Audiofile's Wave Editor and Sound Manager.
- Clicking on the depth/rate value at the bottom left toolbar opens the same sheet. All good.
- When choosing File > Save As… and then in the Save dialog window Format: Settings… button, we can select depth and sample rate again. However, using the same settings as with the aforementioned sheet results in a relatively "heavily"* aliased conversion. Is it a different SRC or just different quality preset? If the available settings appear to be the same, then the result should also be the same.
1 & 2: Swept_24_Amadeus2.8.4_CharacteristicsResample.png
3: Swept_24_Amadeus2.8.4_SaveAsSettings.png
Spectrograms made with Izotope RX8 Elements, with settings attempting to match the spectrograms on https://src.infinitewave.ca
For the record: Izotope RX8 Elements cannot do SRC. I'd have to upgrade to the Standard edition to get it.
*) The difference is not necessarily audible when using the test file, but within a real world workflow, such side effects may eventually multiply…