Fixed RTP streaming - it is now provided by an RTSP relay MediaMTX

dependencies/build_dependencies

@@ -14,12 +14,14 @@ sudo apt-get install -y \
 # RedHat:
 #sudo dnf install pulseaudio-libs-devel gtk3-devel freeglut-devel
 
-
 # These are necessary for building the python bindings for SoapySDR.
 # These must be installed before building SoapySDR for the python
 # bindings to be available on the system.
 sudo apt-get install -y python-dev swig
 
+# These are required for building Soapy RTL-SDR
+sudo apt-get install -y rtl-sdr librtlsdr-dev
+
 
 # Build SoapySDR
 if ! [ -d SoapySDR ]; then
@@ -43,10 +45,21 @@ pushd SoapySDRPlay
     mkdir build
     pushd build
         cmake .. -DCMAKE_BUILD_TYPE=Release
-        make
+        make -j
+        sudo make install
+    popd
+popd
+fi
+
+# Build SoapyRTLSDR plugin
+if ! [ -d SoapyRTLSDR ]; then
+git clone https://github.com/pothosware/SoapyRTLSDR.git
+pushd SoapyRTLSDR
+    mkdir build
+    pushd build
+        cmake .. -DCMAKE_BUILD_TYPE=Release
+        make -j
         sudo make install
-        sudo ldconfig
-        SoapySDRUtil --info
     popd
 popd
 fi
@@ -69,6 +82,13 @@ pushd liquid-dsp
 popd
 fi
 
+# Get mediamtx (no system package available)
+mkdir -p mediamtx
+pushd mediamtx
+    wget https://github.com/aler9/mediamtx/releases/download/v0.22.2/mediamtx_v0.22.2_linux_amd64.tar.gz
+    tar -xzvf mediamtx_v0.22.2_linux_amd64.tar.gz
+popd
+
 echo "Setup completed." >> build.log
 date >> build.log
 exit 0

microservice.py

@@ -3,14 +3,16 @@
 import SoapySDR as soapy
 from radio import Radio
 
-from flask import Flask, request, jsonify
+from flask import Flask, jsonify
 from flasgger import Swagger
 
+
 app = Flask(__name__)
 swag = Swagger(app)
 
 radios = {}
 
+
 @app.route('/radio/report')
 def report():
     """List radio devices available to the system.
@@ -48,7 +50,7 @@ def connect(radio):
     for device in devices:
         if radio in device.values():
             try:
-                radios[radio] = Radio(device)
+                radios[radio] = Radio(radio, device)
                 return "", 200
             except Exception as e:
                 radios.pop(radio)
@@ -81,7 +83,6 @@ def disconnect(radio):
     else:
         return "Radio not connected", 400
 
-
 @app.route('/radio/<radio>/configure/<frequency>')
 def configure(radio, frequency):
     """Tune the radio to a frequency.
@@ -95,7 +96,7 @@ def configure(radio, frequency):
         type: string
         required: true
       - name: frequency
-        description: Frequency (in Hz) to tune the radio to.
+        description: Frequency (in Hz) to tune the radio to. Suffixing is also supported, ie 87.5M, 108.0M, etc.
         in: path
         type: string
         required: true
@@ -106,16 +107,18 @@ def configure(radio, frequency):
         description: The specified radio is not connected.
     """
     if radio in radios:
-        return jsonify(radios[radio].configure(frequency))
+        if radios[radio].is_streaming():
+            return 'no', 400
+        else:
+            return jsonify(radios[radio].configure(frequency))
     else:
         return "Radio not connected", 400
 
-
 @app.route('/radio/<radio>/start')
 def start_stream(radio):
-    """Tune the radio to a frequency.
-    You must connect to the radio before attempting to configure it.
-    The radio must be configured before streaming can be started.
+    """Start the radio stream.
+    Once the stream has been started, connect to the stream at:
+    rtsp://[host]:8554/radio/[radio]/stream
     ---
     parameters:
       - name: radio
@@ -132,9 +135,7 @@ def start_stream(radio):
 
 @app.route('/radio/<radio>/end')
 def end_stream(radio):
-    """Tune the radio to a frequency.
-    You must connect to the radio before attempting to configure it.
-    The radio must be configured before streaming can be started.
+    """Terminate the radio stream.
     ---
     parameters:
       - name: radio
@@ -151,8 +152,23 @@ def end_stream(radio):
 
 
 if __name__ == '__main__':
+    import subprocess
+
+    rtsp_relay = subprocess.Popen(
+        [
+            './dependencies/mediamtx/mediamtx',
+            './dependencies/mediamtx/mediamtx.yml'
+        ],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL
+    )
+
     app.run(
         host='0.0.0.0',
         threaded=True,
         debug=False
     )
+
+    print('Killing RTSP relay...')
+    rtsp_relay.kill()
+    rtsp_relay.wait() # Necessary?

radio.py

@@ -3,7 +3,6 @@ import SoapySDR as soapy
 import prefixed
 from formats import *
 import sys
-import os
 import subprocess
 import struct
 
@@ -11,9 +10,10 @@ import struct
 class Radio:
     FORMAT = 'CS16'
     SAMPLES = 8192
-    PORT = 5002
+    PORT = 8554
 
-    def __init__(self, device_info):
+    def __init__(self, name, device_info):
+        self.name = name
         self.device_info = device_info
         self.run = False
         self.thread = None
@@ -23,6 +23,9 @@ class Radio:
             raise RuntimeError("Failed to connect to radio device")
 
     def configure(self, frequency):
+        if self.is_streaming():
+            raise RuntimeError("Cannot configure radio while a stream is active")
+
         frequency = int(prefixed.Float(frequency))
         sample_rate = 384000
         bandwidth = 200000
@@ -41,6 +44,9 @@ class Radio:
             'gain-mode': 'auto' if self.device.getGainMode(soapy.SOAPY_SDR_RX, 0) else 'manual',
         }
 
+    def is_streaming(self):
+        return (self.thread and self.thread.is_alive())
+
     def start_stream(self):
         if self.thread:
             raise RuntimeError('Stream thread is already running')
@@ -77,7 +83,10 @@ class Radio:
 
     def _init_stream(self):
         self.playback = subprocess.Popen(
-            ['/usr/bin/ffmpeg', '-f', 's16le', '-ar', '32000', '-ac', '2', '-i', '-', '-f', 'rtp', f'rtp://0.0.0.0:{Radio.PORT}'],
+            [
+                '/usr/bin/ffmpeg', '-f', 's16le', '-ar', '32000', '-ac', '2', '-i', '-',
+                '-f', 'rtsp', f"rtsp://localhost:{Radio.PORT}/radio/{self.name}/stream"
+            ],
             stdin=subprocess.PIPE,
             stdout=subprocess.DEVNULL,
             stderr=subprocess.DEVNULL
@@ -100,8 +109,15 @@ class Radio:
         self.device.closeStream(self.stream)
         self.buffer = None
 
+        # .terminate()/.kill() followed by .wait() is required to properly clear
+        # killed zombie processes from the process table.
+        # https://stackoverflow.com/a/41961462
         self.demod.kill()
+        self.demod.wait()
+        self.demod = None
         self.playback.kill()
+        self.playback.wait()
+        self.playback = None
 
 
 """
@@ -110,7 +126,7 @@ Quick and dirty test of the Radio class.
 if __name__ == '__main__':
     import time
 
-    sdr = Radio({'driver': 'sdrplay'})
+    sdr = Radio('demo', {'driver': 'sdrplay'})
 
     print('Configuring...')
     sdr.configure('105.5M')