Assume a 2-bit midrise quantizer with (voltage,codeword) pairs (-3,0),(-1,1),(1,2),(3,3) where step size delta is clearly 2V. Now, calculating PSQNR using the intervals, we have 20log_10(V_peak/qnoise_peak) so Vmax = 3V or 1.5delta. Of course quantization peak error is delta/2 so I should have 1.5delta/(delta/2)=3 in the log.
Here's the problem: textbooks and almost every tutorial I saw take 2^qbits=2^2=4 inside the log function. I feel like the number of levels(4) gets confused with the number of intervals(3). I'm pretty sure I'm the mistaken one, can you explain me how?