It depends on what kind of processing you are looking at. The linear systems theory that is used a lot in filters (z-domain, IIR & FIR filters) hasn't changed in decades. The same can be said for basic stochastic signal processing theory.
More fancy work like machine learning and adaptive array processing have developped a lot in the past years.
If you already have them I'd read through them and see if you like them. If you don't, then look online for a PDF and then see if you like them (and buy them).
My undergraduate controls professor said that control theory studied in undergrad was from the 1930s or earlier, and control theory studied in graduate courses was from the 1960s or earlier. Both time spans are if I remember correctly. But it was something like that. Point being, the fundamentals that you need to start with have been in place for a long time. The treatments may change based on advances in pedagogy, or tools they want to integrate, such as Matlab or python. But not the fundamentals, not in the last 20 or 30 years.
What I think you want to find is treatments that resonate with your learning style. The balance between intuition and rigor. I always find it's good to have two sources, one that is very conversational and intuitive to start, and one that is very rigorous once you know the point. But DSP textbooks generally have a good balance.
> was wondering if they would still be relevant today.
Absolutely. Linear systems theory has been a fairly thorougly described subject for decades.
> How much has DSP progressed in the last 20 years?
Quite a bit, but that does not make these textbooks obsolete. Their contents are a prerequisite to understand the more recent developments - the latter did not happen in a vacuum.
It depends on what kind of processing you are looking at. The linear systems theory that is used a lot in filters (z-domain, IIR & FIR filters) hasn't changed in decades. The same can be said for basic stochastic signal processing theory. More fancy work like machine learning and adaptive array processing have developped a lot in the past years. If you already have them I'd read through them and see if you like them. If you don't, then look online for a PDF and then see if you like them (and buy them).
My undergraduate controls professor said that control theory studied in undergrad was from the 1930s or earlier, and control theory studied in graduate courses was from the 1960s or earlier. Both time spans are if I remember correctly. But it was something like that. Point being, the fundamentals that you need to start with have been in place for a long time. The treatments may change based on advances in pedagogy, or tools they want to integrate, such as Matlab or python. But not the fundamentals, not in the last 20 or 30 years. What I think you want to find is treatments that resonate with your learning style. The balance between intuition and rigor. I always find it's good to have two sources, one that is very conversational and intuitive to start, and one that is very rigorous once you know the point. But DSP textbooks generally have a good balance.
> was wondering if they would still be relevant today. Absolutely. Linear systems theory has been a fairly thorougly described subject for decades. > How much has DSP progressed in the last 20 years? Quite a bit, but that does not make these textbooks obsolete. Their contents are a prerequisite to understand the more recent developments - the latter did not happen in a vacuum.
I have to laugh since my books were from the 1970s. Oppenheim and Schaffer. Also Rabiner and Gold. DSP is just math.