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You have a slight misunderstanding here about the phase shift bit. Technically filters don't cause phase shift, phase shift causes filters. That means in the
by atoav 1y ago
You have a slight misunderstanding here about the phase shift bit.
Technically filters don't cause phase shift, phase shift causes filters.
That means in the analog world all realtime filters come with phase shift, if they didn't you wouldn't have a filter.
In the digital world there is a thing called linear-phase mode where clever people found ways of building filters that shift the phase of the whole signal the same way (involves running the signal through forwarwards and backwards through special filters). If you now have an audio program that deals correctly with the latency introduced by each effect, you can shift the rest by the same amount meaning you bought yourself a linear phase response with added latency (a small delay) on everything. Remember: Humans can't really hear phase smears unless they happen in relation to another thing that is in phase. This only happens when you mix two signals. The result of that mix is yet again a filter (e.g. comb filters).
With filters everything is a trade off all the time, but again phase shift is not a just a bad side effect of a filter, it is the mechanism by which it does the work. And sometimes the phase shift introduced cannot be heard.
- Aldipower 1y agoAnd also linear phase isn't for free, besides the latency, it also adds pre-ringing, which especially in the lower frequencies can be very audible and annoying.
- Sesse__ 1y agoFWIW, you don't need to run forwards and backwards to get linear phase. Any symmetric FIR filter will do.
- rcxdude 1y agoYeah, there's a difference between linear phase (which you can achieve with a causal filter, i.e. one that is running in real-time) and constant-phase, which requires that you have more or less the whole signal before you filter it (you can approximate it to the extent you're willing to add more latency).
- atoav 1y agoGood addition. I mentioned the forward/backward bit as this was a way to achieve linear phase in analog times eith more conventional filters (although the cost here was even higher with the additional added noise floor due to tape noise ad the extra work involved).