From 6784afcddc5176e939b39b289e1a1d9b028dba01 Mon Sep 17 00:00:00 2001 From: Aaron Viets <aaron.viets@ligo.org> Date: Thu, 21 Mar 2019 12:45:47 -0700 Subject: [PATCH] calibration_parts.py: added linear-phase filter to shift timestamps by fractions of sample period --- .../python/calibration_parts.py | 23 +++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/gstlal-calibration/python/calibration_parts.py b/gstlal-calibration/python/calibration_parts.py index 348a5ff57d..14f2a3a115 100644 --- a/gstlal-calibration/python/calibration_parts.py +++ b/gstlal-calibration/python/calibration_parts.py @@ -513,6 +513,29 @@ def bandstop(pipeline, head, rate, length = 1.0, f_low = 100, f_high = 400, filt # Now apply the filter return mkcomplexfirbank(pipeline, head, latency = int((length - 1) * 2 * filter_latency + 0.5), fir_matrix = [bandstop], time_domain = td) +def linear_phase_filter(pipeline, head, shift_samples, num_samples = 257): + # Apply a linear-phase filter to shift timestamps. shift_samples is the number + # of samples of timestamp shift. It need not be an integer. A positive value + # advances the output data relative to the timestamps, and a negative value + # delays the output. + + # Prefer an odd filter length + num_samples = int(num_samples) + (1 - int(num_samples) % 2) + + filter_latency_samples = int(num_samples / 2) + numpy.floor(shift_samples) + fractional_shift_samples = shift_samples % 1 + + # Make a filter using a sinc table, slightly shifted relative to the samples + sinc_arg = numpy.arange(-int(num_samples / 2), 1 + int(num_samples / 2)) + fractional_shift_samples + sinc_filter = numpy.sinc(sinc_arg) + # Apply a Blackman window + sinc_filter *= numpy.blackman(num_samples) + # Normalize the filter + sinc_filter /= numpy.sum(sinc_filter) + + # Filter the data + return mkcomplexfirbank(pipeline, head, latency = filter_latency_samples, fir_matrix = [sinc_filter[::-1]], time_domain = True) + def compute_rms(pipeline, head, rate, average_time, f_min = None, f_max = None, filter_latency = 0.5, rate_out = 16, td = True): # Find the root mean square amplitude of a signal between two frequencies # Downsample to save computational cost -- GitLab