Add VAD examples using ALSA for recording (#739)

python-api-examples/vad-alsa.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+
+"""
+This script works only on Linux. It uses ALSA for recording.
+"""
+
+import argparse
+from pathlib import Path
+
+import sherpa_onnx
+
+
+def get_args():
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.ArgumentDefaultsHelpFormatter
+    )
+
+    parser.add_argument(
+        "--silero-vad-model",
+        type=str,
+        required=True,
+        help="Path to silero_vad.onnx",
+    )
+
+    parser.add_argument(
+        "--device-name",
+        type=str,
+        required=True,
+        help="""
+The device name specifies which microphone to use in case there are several
+on your system. You can use
+
+  arecord -l
+
+to find all available microphones on your computer. For instance, if it outputs
+
+**** List of CAPTURE Hardware Devices ****
+card 3: UACDemoV10 [UACDemoV1.0], device 0: USB Audio [USB Audio]
+  Subdevices: 1/1
+  Subdevice #0: subdevice #0
+
+and if you want to select card 3 and the device 0 on that card, please use:
+
+  plughw:3,0
+
+as the device_name.
+        """,
+    )
+
+    return parser.parse_args()
+
+
+def main():
+    args = get_args()
+    if not Path(args.silero_vad_model).is_file():
+        raise RuntimeError(
+            f"{args.silero_vad_model} does not exist. Please download it from "
+            "https://github.com/snakers4/silero-vad/blob/master/files/silero_vad.onnx"
+        )
+
+    device_name = args.device_name
+    print(f"device_name: {device_name}")
+    alsa = sherpa_onnx.Alsa(device_name)
+
+    sample_rate = 16000
+    samples_per_read = int(0.1 * sample_rate)  # 0.1 second = 100 ms
+
+    config = sherpa_onnx.VadModelConfig()
+    config.silero_vad.model = args.silero_vad_model
+    config.sample_rate = sample_rate
+
+    vad = sherpa_onnx.VoiceActivityDetector(config, buffer_size_in_seconds=30)
+
+    print("Started! Please speak. Press Ctrl C to exit")
+
+    printed = False
+    k = 0
+    try:
+        while True:
+            samples = alsa.read(samples_per_read)  # a blocking read
+
+            vad.accept_waveform(samples)
+
+            if vad.is_speech_detected() and not printed:
+                print("Detected speech")
+                printed = True
+
+            if not vad.is_speech_detected():
+                printed = False
+
+            while not vad.empty():
+                samples = vad.front.samples
+                duration = len(samples) / sample_rate
+                filename = f"seg-{k}-{duration:.3f}-seconds.wav"
+                k += 1
+                sherpa_onnx.write_wave(filename, samples, sample_rate)
+                print(f"Duration: {duration:.3f} seconds")
+                print(f"Saved to {filename}")
+                print("----------")
+
+                vad.pop()
+    except KeyboardInterrupt:
+        print("\nCaught Ctrl + C. Exit")
+
+
+if __name__ == "__main__":
+    main()