Yes, I expected Opus to resample to 48 kHz internally. The question was more: if it does, will the CELT coder know that the input was upsampled from 32 kHz by the Speex resampler, and limit its encoding bandwidth to 16 kHz (the bandwidth of the original input file), or is the 20-kHz bandwidth of high-bitrate CELT hard-coded regardless of the input sampling rate?
why not resample everything to 40kHz instead of 48.
I think the CELT layer in Opus (possibly not in the old CELT codec) works also at 24kHz sampling rate (12kHz bandwidth) - and this is used at least for the 8-12kHz part of the spectrum in the hybrid mode.
That's the theory, but does it *really* behaves that way in the OPUS encoder builds provided by the Xiph staff ?
Thats the problem with these totally opaque closed source programs, it's completely impossible to tell what they really do... you can only speculate about it on forums.
You tell us. You even mentioned listening tests. Questions like this are precisely why they exist.
For listening test (wav file).If I resample to 44.1 kHz with SoX (sox any-file outfile rate 44100) is this audible?