Bug? 2 Sample Rate Converters = 2 different results

[Lou Kash]

AP has a few ways to convert sample rate, but the results are not the same.

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:

1. 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.
2. Clicking on the depth/rate value at the bottom left toolbar opens the same sheet. All good.
3. 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.

Thanks

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…

[Martin Hairer]

Which file format did you save to? If it wasn't a lossless format, you may just be seeing artefacts from the compression, rather than the rate conversion.

[Lou Kash]

Which file format did you save to?

Exactly as per https://src.infinitewave.ca/faq.html

• Downloaded http://src.infinitewave.ca/TestSignals.zip
• Opened Swept_24.wav in AP
• Resampled/saved as 24/44.1 WAV

The only difference is that in the first example the resample was done "inline" via Sound > Characteristics and then a plain Save As, whereas the other example was resampled during the Save As process via Format: Wave > Settings
Should give the same result by all means of logic but it doesn't.

[Martin Hairer]

Sorry, I cannot reproduce this, both resampling methods give me identical sonograms:

[Lou Kash]

Is it a MacOS issue? My tests were on El Capitan. But I can try up to Catalina or anything inbetween.