You are NOT doing (what everyone else calls) bit-reduction here. Bit-reduction is when you reduce the number of bits used to represent a sample. Instead you are (logically) decimating the signal to 1/4th of the sampling rate and then zero-stuffing it back to the original rate. The decimation step will cause anything above 1/8th of the sampling rate to alias down, but assuming the signal bandwidth is low enough to fit, it can be reconstructed by sinc-interpolation... except you need the sinc-cutoff at 1/8th of the sampling rate (instead of half sampling-rate like your picture above) because you are logically upsampling.Nowhk wrote:Visually, it seems to me that the input signal (2hz) is vanished. But I could be wrong.
So quantization (probably) do mess the original 2hz signal's frequency.
But again.. none of this has anything to do with bit-depth and the sooner you admit that the sooner you'll get somewhere.