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src/aes67_source.py

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+#!/usr/bin/env python3
+"""
+AES67 Source Example (Microphone to Network RTP @ 48 kHz)
+
+This script enumerates local microphone devices (GStreamer "Audio/Source")
+and lets you pick one to publish as an AES67-compatible RTP multicast stream.
+
+It also advertises the stream via SAP so that receivers on the same subnet can
+automatically discover and subscribe.
+
+Tested with GStreamer 1.24 and Python 3.12.
+
+Usage:
+  python aes67_source.py [--multicast 239.255.0.1] [--port 5004]
+
+Requirements:
+  • PyGObject bindings for GStreamer (pip install pygobject)
+  • The corresponding GStreamer runtime with "good" plugins.
+
+Copyright 2025 © Patrick Struebi
+"""
+from __future__ import annotations
+
+import argparse
+import sys
+from typing import List
+from sap_discovery import discover_sinks
+
+import gi
+
+gi.require_version("Gst", "1.0")
+from gi.repository import Gst  # noqa: E402
+from gi.repository import GLib  # noqa: E402
+
+Gst.init(None)
+
+
+def enumerate_audio_sources() -> List[Gst.Device]:
+    """Return a list of microphone devices recognised by GStreamer."""
+    monitor = Gst.DeviceMonitor()
+    # Filter for capture sources (microphones)
+    monitor.add_filter("Audio/Source")
+    monitor.start()
+    devices = monitor.get_devices()
+    monitor.stop()
+    return devices
+
+
+def prompt_for_device(devices: List[Gst.Device], prompt: str) -> Gst.Device:
+    if not devices:
+        print("No audio input devices found.")
+        sys.exit(1)
+    if len(devices) == 1:
+        print(f"Auto-selected only available input device: {devices[0].get_display_name()}")
+        return devices[0]
+    print(prompt)
+    for idx, dev in enumerate(devices):
+        print(f"[{idx}] {dev.get_display_name()}")
+    while True:
+        try:
+            choice = int(input("Select device #: "))
+            if 0 <= choice < len(devices):
+                return devices[choice]
+        except ValueError:
+            pass
+        print("Invalid selection, try again.")
+
+
+def build_pipeline(device: Gst.Device, multicast: str, port: int) -> Gst.Pipeline:
+    """Construct the GStreamer pipeline string and create a pipeline."""
+
+    # Attempt to extract a gst-launch-compatible device string
+    dev_props = device.get_properties() or {}
+    device_str = None
+    if dev_props:
+        # Common property names depending on backend
+        for key in ("device", "device.path", "device.string"):
+            if dev_props.has_field(key):
+                device_str = dev_props.get_string(key)
+                break
+    # Fallback to auto-selection if we cannot determine the exact string
+    if device_str:
+        src = f"pulsesrc device={device_str}"
+    else:
+        src = "autoaudiosrc"
+
+    # AES67 requires 48 kHz, 16-bit, 2-channel PCM
+    pipeline_description = (
+        f"{src} ! audioconvert ! audioresample ! audio/x-raw,channels=2,rate=48000 "
+        "! rtpL16pay ! multiudpsink clients="
+        f"{multicast}:{port} sync=false"
+    )
+
+    print("GStreamer pipeline:")
+    print(pipeline_description, "\n")
+
+    pipeline = Gst.parse_launch(pipeline_description)
+    return pipeline  # type: ignore[return-value]
+
+
+
+
+
+
+def prompt_for_sink(sinks):
+    if not sinks:
+        print("No sinks discovered via SAP announcements.")
+        sys.exit(1)
+    if len(sinks) == 1:
+        print(f"Auto-selected only discovered sink: {sinks[0].get('name', 'Unknown')} @ {sinks[0].get('address', '?')}:{sinks[0].get('port', '?')}")
+        return sinks[0]
+    print("Discovered sinks:")
+    for idx, sink in enumerate(sinks):
+        name = sink.get('name', 'Unknown')
+        addr = sink.get('address', '?')
+        port = sink.get('port', '?')
+        print(f"[{idx}] {name} @ {addr}:{port}")
+    while True:
+        try:
+            sel = int(input("Select sink #: "))
+            if 0 <= sel < len(sinks):
+                return sinks[sel]
+        except ValueError:
+            pass
+        print("Invalid selection, try again.")
+
+def main():
+    parser = argparse.ArgumentParser(description="AES67 Source (Microphone)")
+    parser.add_argument("--sap-wait", type=float, default=5.0, help="Seconds to listen for SAP sinks")
+    args = parser.parse_args()
+
+    print("Listening for SAP announcements...")
+    sinks = discover_sinks(timeout=args.sap_wait)
+    sink = prompt_for_sink(sinks)
+    multicast = sink['address']
+    port = int(sink['port'])
+
+    devices = enumerate_audio_sources()
+    mic = prompt_for_device(devices, "Available microphone devices:")
+
+    pipeline = build_pipeline(mic, multicast, port)
+
+    loop = GLib.MainLoop()
+
+    def on_message(_, msg):
+        t = msg.type
+        if t == Gst.MessageType.EOS:
+            print("End-of-Stream reached.")
+            loop.quit()
+        elif t == Gst.MessageType.ERROR:
+            err, dbg = msg.parse_error()
+            print("Pipeline error:", err, dbg)
+            loop.quit()
+
+    bus = pipeline.get_bus()
+    bus.add_signal_watch()
+    bus.connect("message", on_message)
+
+    ret = pipeline.set_state(Gst.State.PLAYING)
+    if ret == Gst.StateChangeReturn.FAILURE:
+        print("Failed to start pipeline.")
+        sys.exit(1)
+
+    print(f"Streaming to {multicast}:{port}… Press Ctrl+C to stop.")
+    try:
+        loop.run()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        pipeline.set_state(Gst.State.NULL)
+
+
+if __name__ == "__main__":
+    main()