newbie audio questions

[Guest]

I'm a video guy. Audio is a big mystery to me. Anyway, here goes...

So if we sample at 48kHz, does that mean we represent only frequencies at 24kHz and below? I think so but please confirm.

Now, if my capture device (DC10+ and AVI_IO) says it can capture only 24kHz PCM does that mean the highest audible frequency or sampling rate?

Suppose it means sampling rate. Then I am only getting 12kHz and below in audible frequencies?

Suppose I am getting just 24kHz sampling. Should I up convert it to 48kHz before encoding to MP3 with lame? And what bit rate should I use?

Sorry lotsa questions. :)

[DJ Bobo]

Yes, 48KHz sampling means frequencies up to 24KHz.

Don't know what your card means, just open the audio file in Winamp or something and see which samplerate is being used.

And yes, 24KHz sampling means frequencies up to 12KHz.

If you want MP3 only (not combined with video), you don't need to resample.
If you want MP3 for video, you better upsample to 32KHz to avoid synch issues related with MPEG-2 compliant compression (upsampling to 48KHz won't bring anything, it will make compression only less efficient!).
For Stereo sound sampled @32KHz, I suggest you use 80kbps or higher. You can use "--alt-preset x" for higher quality than normal cbr encoding (where x is the desired bitrate).