颤振:如何将麦克风的原始音频信号实时输入内存？

Question

标题说明了一切。这样做是为了监测周围的噪音。一旦检测到某种模式，就应该将音频信号记录到文件中。困难在于，记录的文件应该在检测到模式之前几秒钟启动。因此，在内存中需要音频信号才能“返回”几秒钟。你知道如何实时地把原始音频输入到内存中吗？

Answer 1

你可以使用颤振声音插件，使麦克风的原始音频信号进入内存实时。参考链接是：声音，演示示例在这里，body.dart

我有一个例子是

Widget _buildRecorder(Track track) {
    return Padding(
        padding: const EdgeInsets.all(8.0),
        child: RecorderPlaybackController(
            child: Column(
          children: [
            Left("Recorder"),
            SoundRecorderUI(track),
            Left("Recording Playback"),
            SoundPlayerUI.fromTrack(
              track,
              enabled: false,
              showTitle: true,
              audioFocus: true
                  ? AudioFocus.requestFocusAndDuckOthers
                  : AudioFocus.requestFocusAndDuckOthers,
            ),
          ],
        )));
  }

}

Answer 2

流包可以帮助您将麦克风音频作为PCM格式的Stream<Uint8List>进行流。假设您拥有每秒16000个示例，您可以使用它创建一个产生n个音频块的流：

import 'dart:math'; // for min
import 'dart:typed_data'; // for Uint8List
import 'package:sound_stream/sound_stream.dart';

Stream<Uint8List> audioChunks([int seconds = 3]) async* {
  final stream = RecorderStream();
  await stream.initialize();
  stream.start();

  BytesBuilder buffer = BytesBuilder();
  int filled = 0;
  int max = seconds * 16000 * 2; // pcm 16bit = 2bytes / sample

  await for (final chunk in stream.audioStream) {
    int cl = min(max-filled, chunk.length);
    buffer.add(chunk.sublist(0, cl));
    filled += cl;
    if (filled == max) {
      yield buffer.toBytes();
      filled = 0;
      buffer.clear();
    }
    if (chunk.length > cl) {
      buffer.add(chunk.sublist(cl));
      filled += chunk.length - cl;
    }
  }
}