| Sad that the thread got flagged into oblivion. > There is a fair amount of academic work describing methods to perform filtering on a sample to provide a fractional delay. One common way is to apply an FIR filter. However, to keep things simple, the method I chose was the Thiran approximation — the literature suggests that it performs the task reasonably well, and has the advantage of not having to spend a whole lot of CPU cycles first transforming to the frequency domain (which an FIR filter requires). I'm not a real DSP expert by any stretch of the imagination, but applying an FIR filter does not require transforming to the frequency domain. To the contrary: a basic FIR filter just means that the ith output sample is a[0]x[i] + a[1]x[i-1] + a[2]x[i-2] + ... + a[N-1]x[i-N+1] where x is the input, a is the filter coefficients, and N+1 is the (finite) length of the filter. (If the input is all zeros except that x[0]=1, then the input is an impulse and a is the output, i.e. the impulse response. Hence the name: Finite Impulse Response.) Some very long FIR filters are more efficient to apply by Fourier transforming the input, but that's almost certainly not the case here. It's worth noting that FIR filters vectorize very nicely. (My FIR description isn't quite 100% accurate. I described only the discrete-time causal case. If you drop the causality requirement (which is fine but can be awkward in real-time processing) then you add negative indices to a. If you switch to continuous time, you end up with a convolution instead of a sum of products.) |
I sometimes feel the PC threshold is a bit high in some threads. In this case however even I felt the snark level was painful.
As a productive engineer I often put out internal tools or POCs that would be possible to snark at in this way.
I do however expect that people improve them or explain the better way instead of posting dismissive comments on what this guy has done on top of his open source contributions.
That said: I'm happy to see it reposted although I would prefer if he removed the defence for his previous post as it did add confusion to the new post as well.