first stab at ft8 decoding: chop up audio, call jt9 binary to decode

csdr.py

@@ -21,11 +21,11 @@ OpenWebRX csdr plugin: do the signal processing with csdr
 """
 
 import subprocess
-import time
 import os
 import signal
 import threading
 from functools import partial
+from owrx.wsjt import Ft8Chopper
 
 import logging
 logger = logging.getLogger(__name__)
@@ -186,6 +186,12 @@ class dsp(object):
                     "csdr timing_recovery_cc GARDNER {secondary_samples_per_bits} 0.5 2 --add_q | " + \
                     "CSDR_FIXED_BUFSIZE=1 csdr dbpsk_decoder_c_u8 | " + \
                     "CSDR_FIXED_BUFSIZE=1 csdr psk31_varicode_decoder_u8_u8"
+        elif which == "ft8":
+            chain =  secondary_chain_base + "csdr realpart_cf | "
+            if self.last_decimation != 1.0 :
+                chain += "csdr fractional_decimator_ff {last_decimation} | "
+            chain += "csdr agc_ff | csdr limit_ff | csdr convert_f_s16"
+            return chain
 
     def set_secondary_demodulator(self, what):
         if self.get_secondary_demodulator() == what:
@@ -238,7 +244,8 @@ class dsp(object):
             secondary_samples_per_bits=self.secondary_samples_per_bits(),
             secondary_bpf_cutoff=self.secondary_bpf_cutoff(),
             secondary_bpf_transition_bw=self.secondary_bpf_transition_bw(),
-            if_samp_rate=self.if_samp_rate()
+            if_samp_rate=self.if_samp_rate(),
+            last_decimation=self.last_decimation
             )
 
         logger.debug("[openwebrx-dsp-plugin:csdr] secondary command (fft) = %s", secondary_command_fft)
@@ -253,6 +260,10 @@ class dsp(object):
         self.secondary_processes_running = True
 
         self.output.add_output("secondary_fft", partial(self.secondary_process_fft.stdout.read, int(self.get_secondary_fft_bytes_to_read())))
+        if self.get_secondary_demodulator() == "ft8":
+            chopper = Ft8Chopper(self.secondary_process_demod.stdout)
+            chopper.start()
+        else:
             self.output.add_output("secondary_demod", partial(self.secondary_process_demod.stdout.read, 1))
 
         #open control pipes for csdr and send initialization data
@@ -262,7 +273,7 @@ class dsp(object):
 
     def set_secondary_offset_freq(self, value):
         self.secondary_offset_freq=value
-        if self.secondary_processes_running:
+        if self.secondary_processes_running and hasattr(self, "secondary_shift_pipe_file"):
             self.secondary_shift_pipe_file.write("%g\n"%(-float(self.secondary_offset_freq)/self.if_samp_rate()))
             self.secondary_shift_pipe_file.flush()
 
@@ -332,6 +343,8 @@ class dsp(object):
     def get_audio_rate(self):
         if self.isDigitalVoice():
             return 48000
+        elif self.secondary_demodulator == "ft8":
+            return 12000
         return self.get_output_rate()
 
     def isDigitalVoice(self, demodulator = None):

htdocs/index.html

@@ -109,6 +109,7 @@
                         <select id="openwebrx-secondary-demod-listbox" onchange="secondary_demod_listbox_changed();">
                             <option value="none"></option>
                             <option value="bpsk31">BPSK31</option>
+                            <option value="ft8">FT8</option>
                         </select>
                     </div>
                     <div class="openwebrx-panel-line">

htdocs/openwebrx.js

@@ -2633,6 +2633,7 @@ function demodulator_digital_replace(subtype)
     {
     case "bpsk31":
     case "rtty":
+    case "ft8":
         secondary_demod_start(subtype);
         demodulator_analog_replace('usb', true);
         demodulator_buttons_update();
@@ -2809,6 +2810,9 @@ function secondary_demod_listbox_changed()
         case "rtty":
             demodulator_digital_replace('rtty');
             break;
+        case "ft8":
+            demodulator_digital_replace('ft8');
+            break;
     }
 }
 

owrx/wsjt.py

@@ -0,0 +1,79 @@
+import threading
+import wave
+from datetime import datetime, timedelta
+import time
+import sched
+import subprocess
+
+import logging
+logger = logging.getLogger(__name__)
+
+
+class Ft8Chopper(threading.Thread):
+    def __init__(self, source):
+        self.source = source
+        (self.wavefilename, self.wavefile) = self.getWaveFile()
+        self.scheduler = sched.scheduler(time.time, time.sleep)
+        self.queue = []
+        self.doRun = True
+        super().__init__()
+
+    def getWaveFile(self):
+        filename = "/tmp/openwebrx-ft8chopper-{0}.wav".format(datetime.now().strftime("%Y%m%d-%H%M%S"))
+        wavefile = wave.open(filename, "wb")
+        wavefile.setnchannels(1)
+        wavefile.setsampwidth(2)
+        wavefile.setframerate(12000)
+        return (filename, wavefile)
+
+    def getNextDecodingTime(self):
+        t = datetime.now()
+        seconds = (int(t.second / 15) + 1) * 15
+        if seconds >= 60:
+            t = t + timedelta(minutes = 1)
+            seconds = 0
+        t = t.replace(second = seconds, microsecond = 0)
+        logger.debug("scheduling: {0}".format(t))
+        return t.timestamp()
+
+    def startScheduler(self):
+        self._scheduleNextSwitch()
+        threading.Thread(target = self.scheduler.run).start()
+
+    def emptyScheduler(self):
+        for event in self.scheduler.queue:
+            self.scheduler.cancel(event)
+
+    def _scheduleNextSwitch(self):
+        self.scheduler.enterabs(self.getNextDecodingTime(), 1, self.switchFiles)
+
+    def switchFiles(self):
+        file = self.wavefile
+        filename = self.wavefilename
+        (self.wavefilename, self.wavefile) = self.getWaveFile()
+
+        file.close()
+        self.queue.append(filename)
+        self._scheduleNextSwitch()
+
+    def decode(self):
+        if self.queue:
+            file = self.queue.pop()
+            logger.debug("processing file {0}".format(file))
+            #TODO expose decoding quality parameters through config
+            self.decoder = subprocess.Popen(["jt9", "--ft8", "-d", "3", file])
+
+    def run(self) -> None:
+        logger.debug("FT8 chopper starting up")
+        self.startScheduler()
+        while self.doRun:
+            data = self.source.read(256)
+            if data is None or (isinstance(data, bytes) and len(data) == 0):
+                logger.warning("zero read on ft8 chopper")
+                self.doRun = False
+            else:
+                self.wavefile.writeframes(data)
+
+            self.decode()
+        logger.debug("FT8 chopper shutting down")
+        self.emptyScheduler()