If you worry about artifacts introduced by sample rate conversion, you shouldn't use a lossy format in the first place. The sample rate converter used by Opus (i.e., the speex resampler used in the opus-tools library) is completely transparent and does not introduce any audible artifacts. As per [1], the distortion caused by any lossy codec even at the highest bitrates is larger than that caused by re-sampling.
As for playback, most likely your sound card is already running at 48kHz; 44.1kHz may actually not be supported properly by your DAC (I guess since it requires a higher quality anti-aliasing filter). As [1] continues to explain, Opus is essentially shifting the burden of resampling to the encoding rather than the decoding side of things.
That being said, Opus technically supports odd sample rates such as 44.1kHz, but this has to be signalled in a side-channel. See [1] downwards.
Yep, I've read all that before. I didn't mean to focus the discussion on the resampling--what I was trying to get across is, this codec acts differently than codecs that have been extensively tested and ABXed at high bitrates for years. I didn't even mention other factors like how it injects noise into bands on purpose (where you can also find references claiming that's a benefit and not a downside, of course). It was about a year ago, but beyond my own ABX testing I looked around quite a bit, and didn't see many high-bitrate tests out there. All the focus seemed to be on the 64kbit range.
This should not matter to me personally, as I have proven to myself that pretty low bitrates are transparent to me, regardless of the codec. But... I have the same psychosis that a lot of people have, where I think I can hear differences when I know which is which.
If space were an issue I'd use 90kbit/s opus (that was the threshold for me in my testing). It's actually pretty amazing, but since I have the storage space, I archive FLAC and carry around 256kbit/s vorbis, and don't even question the quality. It's easier to use more space than to fix my faulty perception!
As for playback, most likely your sound card is already running at 48kHz; 44.1kHz may actually not be supported properly by your DAC (I guess since it requires a higher quality anti-aliasing filter). As [1] continues to explain, Opus is essentially shifting the burden of resampling to the encoding rather than the decoding side of things.
That being said, Opus technically supports odd sample rates such as 44.1kHz, but this has to be signalled in a side-channel. See [1] downwards.
[1] https://wiki.xiph.org/OpusFAQ#What_is_Opus_Custom.3F
edit: clarity