Recording WAV to IBM Watson Speech-To-Text

Question

I'm trying to record audio and immediately send it to IBM Watson Speech-To-Text for transcription. I've tested Watson with a WAV file loaded from disk, and that worked. On the other end, I've also tested with recording from microphone and storing it to disk, works good too.

But when I try to record the audio with NAudio WaveIn, the result from Watson is empty, as if there's no audio.

Anyone who can shine a light on this, or someone has some ideas?

private async void StartHere()
{
    var ws = new ClientWebSocket();
    ws.Options.Credentials = new NetworkCredential("*****", "*****");

    await ws.ConnectAsync(new Uri("wss://stream.watsonplatform.net/speech-to-text/api/v1/recognize?model=en-US_NarrowbandModel"), CancellationToken.None);

    Task.WaitAll(ws.SendAsync(openingMessage, WebSocketMessageType.Text, true, CancellationToken.None), HandleResults(ws));

    Record();
}

public void Record()
{
    var waveIn = new WaveInEvent
    {
        BufferMilliseconds = 50,
        DeviceNumber       = 0,
        WaveFormat         = format
    };

    waveIn.DataAvailable    += new EventHandler(WaveIn_DataAvailable);
    waveIn.RecordingStopped += new EventHandler(WaveIn_RecordingStopped);
    waveIn.StartRecording();
}

public void Stop() 
{
    await ws.SendAsync(closingMessage, WebSocketMessageType.Text, true, CancellationToken.None);
}

public void Close()
{
    ws.CloseAsync(WebSocketCloseStatus.NormalClosure, "Close", CancellationToken.None).Wait();
}

private void WaveIn_DataAvailable(object sender, WaveInEventArgs e)
{
    await ws.SendAsync(new ArraySegment(e.Buffer), WebSocketMessageType.Binary, true, CancellationToken.None);
}

private async Task HandleResults(ClientWebSocket ws)
{
    var buffer = new byte[1024];

    while (true)
    {
        var segment = new ArraySegment(buffer);
        var result = await ws.ReceiveAsync(segment, CancellationToken.None);

        if (result.MessageType == WebSocketMessageType.Close)
        {
            return;
        }

        int count = result.Count;
        while (!result.EndOfMessage)
        {
            if (count >= buffer.Length)
            {
                await ws.CloseAsync(WebSocketCloseStatus.InvalidPayloadData, "That's too long", CancellationToken.None);
                return;
            }

            segment = new ArraySegment(buffer, count, buffer.Length - count);
            result = await ws.ReceiveAsync(segment, CancellationToken.None);
            count += result.Count;
        }

        var message = Encoding.UTF8.GetString(buffer, 0, count);

        // you'll probably want to parse the JSON into a useful object here,
        // see ServiceState and IsDelimeter for a light-weight example of that.
        Console.WriteLine(message);

        if (IsDelimeter(message))
        {
            return;
        }
    }
}

private bool IsDelimeter(String json)
{
    MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(json));
    DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(ServiceState));
    ServiceState obj = (ServiceState) ser.ReadObject(stream);

    return obj.state == "listening";
}

[DataContract]
internal class ServiceState
{
    [DataMember]
    public string state = "";
}

Edit: I've also tried to send the WAV "header" prior to StartRecording, like this

    waveIn.DataAvailable    += new EventHandler(WaveIn_DataAvailable);
    waveIn.RecordingStopped += new EventHandler(WaveIn_RecordingStopped);

    /* Send WAV "header" first */
    using (var stream = new MemoryStream())
    {
        using (var writer = new BinaryWriter(stream, Encoding.UTF8))
        {
            writer.Write(Encoding.UTF8.GetBytes("RIFF"));
            writer.Write(0); // placeholder
            writer.Write(Encoding.UTF8.GetBytes("WAVE"));
            writer.Write(Encoding.UTF8.GetBytes("fmt "));

            format.Serialize(writer);

            if (format.Encoding != WaveFormatEncoding.Pcm && format.BitsPerSample != 0)
            {
                writer.Write(Encoding.UTF8.GetBytes("fact"));
                writer.Write(4);
                writer.Write(0);
            }

            writer.Write(Encoding.UTF8.GetBytes("data"));
            writer.Write(0);
            writer.Flush();
        }

        byte[] header = stream.ToArray();

        await ws.SendAsync(new ArraySegment(header), WebSocketMessageType.Binary, true, CancellationToken.None);
    }
    /* End WAV header */

    waveIn.StartRecording();

Answer 1

Found the solution after ~20 hours of trial and error, I created a GitHub Gist, because it may be handy for others. See https://gist.github.com/kboek/20476c2a03b5e9188edebaace74f9a07