attempt to reduce cpu usage by pre-selecting parts of the spectrum with

resamplers

owrx/service.py

@@ -1,9 +1,11 @@
 import threading
+import socket
 from owrx.source import SdrService
 from owrx.bands import Bandplan
 from csdr import dsp, output
 from owrx.wsjt import WsjtParser
 from owrx.config import PropertyManager
+from owrx.source import Resampler
 
 import logging
 
@@ -63,28 +65,110 @@ class ServiceHandler(object):
         self.startupTimer = threading.Timer(10, self.updateServices)
         self.startupTimer.start()
 
+    def getAvailablePort(self):
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.bind(("", 0))
+        s.listen(1)
+        port = s.getsockname()[1]
+        s.close()
+        return port
+
     def updateServices(self):
         logger.debug("re-scheduling services due to sdr changes")
         self.stopServices()
         cf = self.source.getProps()["center_freq"]
-        srh = self.source.getProps()["samp_rate"] / 2
+        sr = self.source.getProps()["samp_rate"]
+        srh = sr / 2
         frequency_range = (cf - srh, cf + srh)
-        self.services = [
+
-            self.setupService(dial["mode"], dial["frequency"])
+        dials = [
+            dial
             for dial in Bandplan.getSharedInstance().collectDialFrequencies(frequency_range)
             if self.isSupported(dial["mode"])
         ]
 
-    def setupService(self, mode, frequency):
+        if not dials:
+            logger.debug("no services available")
+            return
+
+        self.services = []
+
+        for group in self.optimizeResampling(dials, sr):
+            frequencies = sorted([f["frequency"] for f in group])
+            min = frequencies[0]
+            max = frequencies[-1]
+            cf = (min + max) / 2
+            bw = max - min
+            logger.debug("group center frequency: {0}, bandwidth: {1}".format(cf, bw))
+            resampler_props = PropertyManager()
+            resampler_props["center_freq"] = cf
+            # TODO the + 24000 is a temporary fix since the resampling optimizer does not account for required bandwidths
+            resampler_props["samp_rate"] = bw + 24000
+            resampler = Resampler(resampler_props, self.getAvailablePort(), self.source)
+            resampler.start()
+            self.services.append(resampler)
+
+            for dial in group:
+                self.services.append(self.setupService(dial["mode"], dial["frequency"], resampler))
+
+    def optimizeResampling(self, freqs, bandwidth):
+        freqs = sorted(freqs, key=lambda f: f["frequency"])
+        distances = [{
+            "frequency": freqs[i]["frequency"],
+            "distance": freqs[i+1]["frequency"] - freqs[i]["frequency"],
+        } for i in range(0, len(freqs)-1)]
+
+        distances = [d for d in distances if d["distance"] > 0]
+
+        distances = sorted(distances, key=lambda f: f["distance"], reverse=True)
+
+
+        def calculate_usage(num_splits):
+            splits = sorted([f["frequency"] for f in distances[0:num_splits]])
+            previous = 0
+            groups = []
+            for split in splits:
+                groups.append([f for f in freqs if previous < f["frequency"] <= split])
+                previous = split
+            groups.append([f for f in freqs if previous < f["frequency"]])
+
+            def get_bandwitdh(group):
+                freqs = sorted([f["frequency"] for f in group])
+                # the group will process the full BW once, plus the reduced BW once for each group member
+                return bandwidth + len(group) * (freqs[-1] - freqs[0] + 24000)
+
+            total_bandwidth = sum([get_bandwitdh(group) for group in groups])
+            return {
+                "num_splits": num_splits,
+                "total_bandwidth": total_bandwidth,
+                "groups": groups,
+            }
+
+
+        usages = [calculate_usage(i) for i in range(0, len(freqs))]
+        # this is simulating no resampling. i haven't seen this as the best result yet
+        usages += [{
+            "num_splits": None,
+            "total_bandwidth": bandwidth * len(freqs),
+            "groups": [freqs]
+        }]
+        results = sorted(usages, key=lambda f: f["total_bandwidth"])
+
+        for r in results:
+            logger.debug("splits: {0}, total: {1}".format(r["num_splits"], r["total_bandwidth"]))
+
+        return results[0]["groups"]
+
+    def setupService(self, mode, frequency, source):
         logger.debug("setting up service {0} on frequency {1}".format(mode, frequency))
         d = dsp(ServiceOutput(frequency))
-        d.nc_port = self.source.getPort()
+        d.nc_port = source.getPort()
-        d.set_offset_freq(frequency - self.source.getProps()["center_freq"])
+        d.set_offset_freq(frequency - source.getProps()["center_freq"])
         d.set_demodulator("usb")
         d.set_bpf(0, 3000)
         d.set_secondary_demodulator(mode)
         d.set_audio_compression("none")
-        d.set_samp_rate(self.source.getProps()["samp_rate"])
+        d.set_samp_rate(source.getProps()["samp_rate"])
         d.start()
         return d
 

owrx/source.py

@@ -274,6 +274,93 @@ class SdrSource(object):
             c.write_spectrum_data(data)
 
 
+class Resampler(SdrSource):
+    def __init__(self, props, port, sdr):
+        sdrProps = sdr.getProps()
+        self.shift = (sdrProps["center_freq"] - props["center_freq"]) / sdrProps["samp_rate"]
+        self.decimation = int(float(sdrProps["samp_rate"]) / props["samp_rate"])
+        if_samp_rate = sdrProps["samp_rate"] / self.decimation
+        self.transition_bw = 0.15 * (if_samp_rate / float(sdrProps["samp_rate"]))
+        props["samp_rate"] = if_samp_rate
+
+        self.sdr = sdr
+        super().__init__(props, port)
+
+    def start(self):
+        self.modificationLock.acquire()
+        if self.monitor:
+            self.modificationLock.release()
+            return
+
+        props = self.rtlProps
+
+        resampler_command = [
+            "nc -v 127.0.0.1 {nc_port}".format(nc_port=self.sdr.getPort()),
+            "csdr shift_addition_cc {shift}".format(shift=self.shift),
+            "csdr fir_decimate_cc {decimation} {ddc_transition_bw} HAMMING".format(
+                decimation=self.decimation,
+                ddc_transition_bw=self.transition_bw,
+            ),
+        ]
+
+        nmux_bufcnt = nmux_bufsize = 0
+        while nmux_bufsize < props["samp_rate"] / 4:
+            nmux_bufsize += 4096
+        while nmux_bufsize * nmux_bufcnt < props["nmux_memory"] * 1e6:
+            nmux_bufcnt += 1
+        if nmux_bufcnt == 0 or nmux_bufsize == 0:
+            logger.error(
+                "Error: nmux_bufsize or nmux_bufcnt is zero. These depend on nmux_memory and samp_rate options in config_webrx.py"
+            )
+            self.modificationLock.release()
+            return
+        logger.debug("nmux_bufsize = %d, nmux_bufcnt = %d" % (nmux_bufsize, nmux_bufcnt))
+        resampler_command += ["nmux --bufsize %d --bufcnt %d --port %d --address 127.0.0.1" % (
+            nmux_bufsize,
+            nmux_bufcnt,
+            self.port,
+        )]
+        cmd = " | ".join(resampler_command)
+        logger.debug("resampler command: %s", cmd)
+        self.process = subprocess.Popen(cmd, shell=True, preexec_fn=os.setpgrp)
+        logger.info("Started resampler source: " + cmd)
+
+        available = False
+
+        def wait_for_process_to_end():
+            rc = self.process.wait()
+            logger.debug("shut down with RC={0}".format(rc))
+            self.monitor = None
+
+        self.monitor = threading.Thread(target=wait_for_process_to_end)
+        self.monitor.start()
+
+        retries = 1000
+        while retries > 0:
+            retries -= 1
+            if self.monitor is None:
+                break
+            testsock = socket.socket()
+            try:
+                testsock.connect(("127.0.0.1", self.getPort()))
+                testsock.close()
+                available = True
+                break
+            except:
+                time.sleep(0.1)
+
+        self.modificationLock.release()
+
+        if not available:
+            raise SdrSourceException("resampler source failed to start up")
+
+        for c in self.clients:
+            c.onSdrAvailable()
+
+    def activateProfile(self, profile_id=None):
+        pass
+
+
 class RtlSdrSource(SdrSource):
     def getCommand(self):
         return "rtl_sdr -s {samp_rate} -f {center_freq} -p {ppm} -g {rf_gain} -"