Samplerate selection to be enhanced

[111MilesToGo]

I have by now succeeded in building the plugin from the source. So I gave it a test drive.

First of all, the sample rate comparison at http://src.infinitewave.ca/ shows that soxr is one of the best SR converters, if not THE best. So your plugin is really valuable.

Unfortunately, I couldn't quite get to grips with your sample rate selection. Please let me explain my use case.

I have a USB-DAC, the Audioquest Dragonfly Red. It does 16 and 24 bits, rates are 44.1, 48, 88.2 and 96 kHz. It can't handle 176.4, 192 and higher rates. In that it is similar to many others.

I tested your soxr as follows:
(1) Automatic checked, 48 / 96 / 192 -> 96, 44.1 / 88.2 / 176.4 -> 88.2
Then 44.1, 48, 88.2 and 96 rates in the FLAC file came in as they should. However, both 176.4 and 192 came in as 96 - very unexpected and ill-chosen!
(2) Automatic NOT checked, otherwise same settings as before
Then the DAC received only 88.2 and 96, respectively, this thing works as expected.

I do think that a sample rate converter should do the following:
In automatic mode, it should bypass conversion for those rates that the DAC handles natively. For rates outside the DAC capabilities, the user should be able to do a sample rate mapping for each sample rate separately, not in groups as you have provided for. Automatic thus means: No sample rate conversion whenever possible, and a precisely selected mapping for the cases which the DAC can't do.
In non-automatic mode, the sample rate converter should follow the full user-provided mapping for all rates.

The Audacious player has a sample rate converter that allows a fully configurable sample rate mapping. Please refer to https://forums.linuxmint.com/viewtopic.php?f=48&t=253225#p1365640 for reference and a screenshot.

So now I have two suggestions for you:
Either, correct the automatic mode so that soxr gets bypassed whenever possible, and the correct sample rate is chosen only when downsampling has to be done. In my case, it should pick 88.2 when 176.4 is in the audio file, and 96 when the file is 192.
Or, provide a full user-selectable mapping for all sample rates (cf. the Audacious screenshot) and let the converter decide when it can bypass and when it needs to convert.

Hope this long write-up is not too convoluted.

Thanks a lot in advance! I repeat myself: Your soxr sample rate converter plugin for DeaDBeeF is a VERY valuable tool. Please consider enhancing it.