Converting to Opus: 44.1 kHz resampled to 48 kHz Options

[gurkburk]

So i have a bunch of regular 44100 flac files that i'de like to convert to OPUS file so i have something to listen to when i run, that's not very hard to setup following this guide.
http://www.saunalahti.fi/~cse/Opus/

What does concern me is that opusenc.exe seems to default to a samplingrate of 48000 when you feed it a raw stream (the '-' option as seen in the guide seems to do that) it's easy to see that the .opus files do indeed become converted/upsampled to 48000hz using this method.
So my question is, should i override this behavior by adding --raw-rate 44100 to the encoder?
Does it matter at all that the files get upsampled? Could it introduce noise or other unwanted side effects?

Thanks

(yes i know that there aren't many android players yet avail for playback of opus, but the question still remains)
Also i think this post belongs to this forums, at least it seemed like it was a good fit, but if i'm wrong please move it :\


This post has been edited by gurkburk: Sep 17 2012, 18:41

[C.R.Helmrich]

I have a similar question as the OP. In my case the input file is at 32 kHz sampling rate, and I want this to be encoded at high rates (i.e. CELT-only). Now there are two ways I can do this:

• Encode the 32-kHz file as-is. This gives me a file decoded at 32 kHz, or decoded at 48 kHz if I specify "--rate 48000" in the decoder command-line.
• Upsample the input to 48 kHz externally, then encode it. This gives me a 48-kHz output file which contains some artificial content between 16 and 20 kHz.

Which of the two approaches is more efficient? Intuitively I would choose the first approach, since that one only encodes content actually present in the input, but maybe CELT is more efficient on 48-kHz than on 32-kHz input (and the 16-20-kHz spectral range consumes almost no bits)?

What do the experts say?

Chris