make wfm deemphasis tau configurable

config_webrx.py

@@ -82,6 +82,13 @@ fft_voverlap_factor = (
 audio_compression = "adpcm"  # valid values: "adpcm", "none"
 fft_compression = "adpcm"  # valid values: "adpcm", "none"
 
+# Tau setting for WFM (broadcast FM) deemphasis\
+# Quote from wikipedia https://en.wikipedia.org/wiki/FM_broadcasting#Pre-emphasis_and_de-emphasis
+# "In most of the world a 50 µs time constant is used. In the Americas and South Korea, 75 µs is used"
+# Enable one of the following lines, depending on your location:
+# wfm_deemphasis_tau = 75e-6  # for US and South Korea
+wfm_deemphasis_tau = 50e-6  # for the rest of the world
+
 digimodes_enable = True  # Decoding digimodes come with higher CPU usage.
 digimodes_fft_size = 2048
 

owrx/dsp.py

@@ -55,6 +55,7 @@ class DspManager(csdr.output, SdrSourceEventClient):
             "center_freq",
             "start_mod",
             "start_freq",
+            "wfm_deemphasis_tau",
         ))
 
         self.dsp = csdr.dsp(self)
@@ -105,6 +106,7 @@ class DspManager(csdr.output, SdrSourceEventClient):
             self.props.wireProperty("digital_voice_unvoiced_quality", self.dsp.set_unvoiced_quality),
             self.props.wireProperty("dmr_filter", self.dsp.set_dmr_filter),
             self.props.wireProperty("temporary_directory", self.dsp.set_temporary_directory),
+            self.props.wireProperty("wfm_deemphasis_tau", self.dsp.set_wfm_deemphasis_tau),
             self.props.filter("center_freq", "offset_freq").wire(set_dial_freq),
         ]