Add Dart API for keyword spotter (#1162)

dart-api-examples/keyword-spotter/bin/init.dart

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+../../vad/bin/init.dart

dart-api-examples/keyword-spotter/bin/zipformer-transducer.dart

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+// Copyright (c)  2024  Xiaomi Corporation
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:args/args.dart';
+import 'package:sherpa_onnx/sherpa_onnx.dart' as sherpa_onnx;
+
+import './init.dart';
+
+void main(List<String> arguments) async {
+  await initSherpaOnnx();
+
+  final parser = ArgParser()
+    ..addOption('encoder', help: 'Path to the encoder model')
+    ..addOption('decoder', help: 'Path to decoder model')
+    ..addOption('joiner', help: 'Path to joiner model')
+    ..addOption('tokens', help: 'Path to tokens.txt')
+    ..addOption('keywords-file', help: 'Path to keywords.txt')
+    ..addOption('input-wav', help: 'Path to input.wav to transcribe');
+
+  final res = parser.parse(arguments);
+  if (res['encoder'] == null ||
+      res['decoder'] == null ||
+      res['joiner'] == null ||
+      res['tokens'] == null ||
+      res['keywords-file'] == null ||
+      res['input-wav'] == null) {
+    print(parser.usage);
+    exit(1);
+  }
+
+  final encoder = res['encoder'] as String;
+  final decoder = res['decoder'] as String;
+  final joiner = res['joiner'] as String;
+  final tokens = res['tokens'] as String;
+  final keywordsFile = res['keywords-file'] as String;
+  final inputWav = res['input-wav'] as String;
+
+  final transducer = sherpa_onnx.OnlineTransducerModelConfig(
+    encoder: encoder,
+    decoder: decoder,
+    joiner: joiner,
+  );
+
+  final modelConfig = sherpa_onnx.OnlineModelConfig(
+    transducer: transducer,
+    tokens: tokens,
+    debug: true,
+    numThreads: 1,
+  );
+  final config = sherpa_onnx.KeywordSpotterConfig(
+    model: modelConfig,
+    keywordsFile: keywordsFile,
+  );
+  final spotter = sherpa_onnx.KeywordSpotter(config);
+
+  final waveData = sherpa_onnx.readWave(inputWav);
+  var stream = spotter.createStream();
+
+  // simulate streaming. You can choose an arbitrary chunk size.
+  // chunkSize of a single sample is also ok, i.e, chunkSize = 1
+  final chunkSize = 1600; // 0.1 second for 16kHz
+  final numChunks = waveData.samples.length ~/ chunkSize;
+
+  for (int i = 0; i != numChunks; ++i) {
+    int start = i * chunkSize;
+    stream.acceptWaveform(
+      samples:
+          Float32List.sublistView(waveData.samples, start, start + chunkSize),
+      sampleRate: waveData.sampleRate,
+    );
+    while (spotter.isReady(stream)) {
+      spotter.decode(stream);
+      final result = spotter.getResult(stream);
+      if (result.keyword != '') {
+        print('Detected: ${result.keyword}');
+      }
+    }
+  }
+
+  // 0.5 seconds, assume sampleRate is 16kHz
+  final tailPaddings = Float32List(8000);
+  stream.acceptWaveform(
+    samples: tailPaddings,
+    sampleRate: waveData.sampleRate,
+  );
+
+  while (spotter.isReady(stream)) {
+    spotter.decode(stream);
+    final result = spotter.getResult(stream);
+    if (result.keyword != '') {
+      print('Detected: ${result.keyword}');
+    }
+  }
+
+  stream.free();
+  spotter.free();
+}