I want to upsample an audio signal by a factor of 8.
The technique I was going to use was to upsample by zero stuffing and then interopolate using a low pass anti-aliasing FIR filter designed using the Remez exchange algorithm.
My question is: what are the design constraints for the Remez algorithm?
My initial thoughts are:
If I have an initial sampling rate of 44100Hz then my new sampling rate will be 352800Hz. When I zero stuff, my spectral content in the range 0-22050Hz will be folder around the new upsampled Nyquist of 176400Hz in the range 154350-176400Hz. So I have the following constraints:
- Sample rate: 352800Hz
- Pass band: 0-22050Hz (0dB)
- Stop band: 154350-176400Hz (-120dB)
This does not produce an very good filter, so my assumption that I only have one spectral image folded around 176400Hz must be incorrect.