31 Aug
2021
31 Aug
'21
4:49 p.m.
On Tue, Aug 31, 2021 at 04:24:43AM +0200, Robin Gareus wrote:
I hoped to sidestep that because the phase-angle
should be a sweepable
parameter. I can probably make this work by cross-fading the computed
FIR when the parameter changes.
Provided that what you want is the same phase angle on all frequencies,
you can easily make it 'sweepable' without recomputing the IR.
The N-point hilbert IR will give you 90 degrees plus a delay of N/2
samples [1]. So in a second channel make a delay of N/2 samples.
Then by combining both in the right proportions you can make any
phase angle you want. For A degrees, just do
out = cos (A) * D + sin (A) * H, where D and H are the delay and
hilbert convolution outputs respectively.
[1] It's not possible to do the phase shift without additional
delay. It's more or less the opposite of a linear phase filter:
for 90 degrees the IR must be anti-symmetric. The lenght of the
hilbert IR determines its bandwidth, the 3 dB points will be
near FS / N and FS / 2 - FS / N. So ideally instead of a delay
for the second channel you should use a FIR with the same
magnitude response as the Hilbert IR.
Ciao,
--
FA