Book review: Audio Effects: Theory, Implementation and Application

I love reading books on signal processing, especially on audio signal processing. From books on using effects to a so-called reference, I still enjoy reading them, even if they are frustrating. The only one that was is DAFX: Digital Audio Effects, but I haven’t made a review of it!

This book came after reading a book on JUCE and starting using it myself. As it was using JUCE for its plugins, I thought it would be a good book.

Discussion

The book starts with a great introduction on signal processing. It actually gives all the theory for linear time invariant filters. Once this is set, I’m not even sure you need more DSP theory!

The second chapters dials back and tackles delays, but with the theoretical approach. It would have actually been better IMHO to give the theory bit by bit, as we don’t need to know anything about the z-transform for any delays. I still think that Zölzer approach on chorus (low-frequency random noise instead of LFO) is the best…

After that, there are two chapters on general LTI effects. First filter design, with all the equations to switch between different types of filters, and then their application to EQ, was-wah and others. It was interesting, but lots of talks and the code quality is… bad. Really, you don’t call modulo in the DSP loop.

The next chapter is yet another mystery: amplitude modulation. The concepts are so basic that it should have been before delays… Not even talking about it.

OK, now the chapter on dynamic processing did introduce compression properly, but the authors forgot that compressors and expanders are more or less the same, and they confused compressor of type I (compressing above threshold) and expander of type II (expanding below threshold) with compressors and expanders. The only thing you can’t do is a compressor of type II, but expanders of type I do exist.

The chapter on overdrive is “cute”. I mean, waveshaping and oversampling, that’s great, but a proper book should tackle analog modeling as well in this kind of chapter…

The following chapter almost tackles vocoders. I mean almost because while starting talking about the theory and short-term FFT, it completely fails at the theory of FFT. It’s quite astonishing when comparing with the first chapter, but seriously, what the authors present as processing assumes a periodic signal. And even then, depending on the FFT window, the result is different. Why didn’t they warn about the fact that this kind of effect is not causal? And after, there are people designing effect directly in the frequency space and completely mess it up. Seriously!

After that chapter, it was all downhill. Spatial audio effects (pan, more or less, with mention of HRTF), the Doppler effect, which is a rehash of the delay chapter with some more information, reverberation (which should have been after delays), a chapter on audio production (the signal path in a condole or a DAW) and then a short chapter on JUCE (so short, that I’m not really sure it matters). I suppose that with my tone, you understand that the second half of the book was a big disappointment.

Conclusion

So there is still no better DSP book than DAFX, and definitely no proper book on DSP programming… Avoid this book, too expensive for what it brings to the table.

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