KFR 7 zero phase filtering using filtfilt

[geoffw64]

Hi Dan,

With KFR 7 installed and running, I'm now trying some of the new features starting with filtfilt. Its signature has an iir_param parameter so it doesn't seem possible to pass a filter containing a series of sections. Is that right?

For room correction I create a set of sections to treat each channel.
At load time:
std::vector<biquad_section> sections;
sections.push_back(...);

I then create a filter using these sections:
iir_filter filter(sections);

At playback time:
filter.apply(samples);
where samples is univector of a size known at run-time.

How can I use filtfilt without running it many times for each channel?
I'm aware there will be a cost associated with two passes and reversing the samples.

KFR 7 is working well and I haven't encountered any playback issues.

Best,
Geoff.

[dancasarin]

Hi Geoff,

As of passing biquad sections to iir_param, it's perfectly possible with one of its constructor. Just construct iir_param(your_vector_of_biquad_sections).

Zero-phase IIR filtering needs the full signal and cannot run in a streaming setup. Using it on chunks creates edge artifacts because the forward–backward pass depends on smooth continuity with both earlier and later samples.

[geoffw64]

Thanks Dan, for both those explanations.