I'm studying some DSP and I'm having trouble understanding the difference between phase delay and group delay.
It seems to me that they both measure the delay time of sinusoids passed through a filter.
- Am I correct in thinking this?
- If so, how do the two measurements differ?
- Could someone give an example of a situation in which one measurement would be more useful than the other?
UPDATE
Reading ahead in Julius Smith's Introduction to Digital Filters, I've found a situation where the two measurements at least give different results: affine-phase filters. That's a partial answer to my question, I guess.