> ## Documentation Index
> Fetch the complete documentation index at: https://assembly-preview.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Transcribe audio from a microphone in C#

> Learn how to transcribe streaming audio in C#.

## Overview

By the end of this tutorial, you'll be able to transcribe audio from your microphone in C#.

<Note>
  Streaming Speech-to-Text is only available for English. See [Supported languages](/docs/getting-started/supported-languages).
</Note>

## Before you begin

To complete this tutorial, you need:

* [.NET 8](https://dotnet.microsoft.com/en-us/download/dotnet/8.0) (earlier versions will work too with minor adjustments)
* An [AssemblyAI account](https://www.assemblyai.com/dashboard/signup) with credit card set up.

Here's the full sample code for what you'll build in this tutorial:

```csharp theme={"system"}
using System.Diagnostics;
using System.Runtime.InteropServices;
using AssemblyAI.Realtime;

// Set up the cancellation token, so we can stop the program with Ctrl+C
var cts = new CancellationTokenSource();
var ct = cts.Token;
Console.CancelKeyPress += (sender, e) => cts.Cancel();

// Set up the realtime transcriber
const int sampleRate = 16_000;
await using var transcriber = new RealtimeTranscriber(new RealtimeTranscriberOptions
{
    ApiKey = "YOUR_API_KEY",
    SampleRate = sampleRate
});

transcriber.SessionBegins.Subscribe(message => Console.WriteLine(
    $"Session begins: \n- Session ID: {message.SessionId}\n- Expires at: {message.ExpiresAt}"
));
transcriber.PartialTranscriptReceived.Subscribe(transcript =>
{
    // don't do anything if nothing was said
    if (string.IsNullOrEmpty(transcript.Text)) return;
    Console.WriteLine($"Partial: {transcript.Text}");
});
transcriber.FinalTranscriptReceived.Subscribe(transcript =>
{
    Console.WriteLine($"Final: {transcript.Text}");
});
transcriber.ErrorReceived.Subscribe(error => Console.WriteLine($"Real-time error: {error.Error}"));
transcriber.Closed.Subscribe(closeEvent =>
    Console.WriteLine("Real-time connection closed: {0} - {1}",
        closeEvent.Code,
        closeEvent.Reason
    )
);

Console.WriteLine("Connecting to real-time transcript service");

await transcriber.ConnectAsync().ConfigureAwait(false);

Console.WriteLine("Starting recording");

var soxArguments = string.Join(' ', [
    // --default-device doesn't work on Windows
    RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "-t waveaudio default" : "--default-device",
    "--no-show-progress",
    $"--rate {sampleRate}",
    "--channels 1",
    "--encoding signed-integer",
    "--bits 16",
    "--type wav",
    "-" // pipe
]);
using var soxProcess = new Process
{
    StartInfo = new ProcessStartInfo
    {
        FileName = "sox",
        Arguments = soxArguments,
        RedirectStandardOutput = true,
        UseShellExecute = false,
        CreateNoWindow = true
    }
};

soxProcess.Start();
var soxOutputStream = soxProcess.StandardOutput.BaseStream;
var buffer = new byte[4096];
while (await soxOutputStream.ReadAsync(buffer, 0, buffer.Length, ct) > 0)
{
    if (ct.IsCancellationRequested) break;
    await transcriber.SendAudioAsync(buffer);
}

soxProcess.Kill();
await transcriber.CloseAsync();
```

## Step 1: Set up a cancellation token

Set up a cancellation token so you can gracefully stop the application.

```csharp theme={"system"}
using System.Diagnostics;
using AssemblyAI.Realtime;

// Set up the cancellation token, so we can stop the program with Ctrl+C
var cts = new CancellationTokenSource();
var ct = cts.Token;
Console.CancelKeyPress += (sender, e) => cts.Cancel();
```

The cancellation token will be cancelled when you press `Ctrl+C`.

## Step 2: Install the AssemblyAI C# .NET SDK

Add the [AssemblyAI NuGet package](https://www.nuget.org/packages/AssemblyAI) to your project:

<CodeGroup>
  ```bash .NET click theme={"system"}
  dotnet add package AssemblyAI
  ```

  ```bash Package Manager theme={"system"}
  Install-Package AssemblyAI
  ```

  ```bash PackageReference theme={"system"}
  <PackageReference Include="AssemblyAI" Version="ASSEMBLYAI_SDK_VERSION" />
  ```
</CodeGroup>

## Step 3: Create a real-time transcriber

In this step, you'll create a real-time transcriber and configure it to use your API key.

<Steps>
  <Step>
    Browse to , and then click the text under **Your API key** to copy it.
  </Step>

  <Step>
    Create a `RealtimeTranscriber` with your API key and a sample rate of 16 kHz. Replace `YOUR_API_KEY` with your copied API key.

    ```csharp theme={"system"}
    // Set up the realtime transcriber
    const int sampleRate = 16_000;
    await using var transcriber = new RealtimeTranscriber(new RealtimeTranscriberOptions
    {
     ApiKey = "YOUR_API_KEY",
     SampleRate = sampleRate
    });
    ```

    <Note>
      The `sampleRate` is the number of audio samples per second, measured in hertz (Hz). Higher sample rates result in higher quality audio, which may lead to better transcripts, but also more data being sent over the network.

      We recommend the following sample rates:

      * Minimum quality: `8_000` (8 kHz)
      * Medium quality: `16_000` (16 kHz)
      * Maximum quality: `48_000` (48 kHz)

      If you don't set a sample rate on the real-time transcriber, it defaults to 16 kHz.
    </Note>
  </Step>

  <Step>
    Subscribe to the different transcriber events and log the event parameters.

    ```csharp theme={"system"}
    transcriber.SessionBegins.Subscribe(message => Console.WriteLine(
     $"Session begins: \n- Session ID: {message.SessionId}\n- Expires at: {message.ExpiresAt}"
    ));
    transcriber.PartialTranscriptReceived.Subscribe(transcript =>
    {
     // don't do anything if nothing was said
     if (string.IsNullOrEmpty(transcript.Text)) return;
     Console.WriteLine($"Partial: {transcript.Text}");
    });
    transcriber.FinalTranscriptReceived.Subscribe(transcript =>
    {
     Console.WriteLine($"Final: {transcript.Text}");
    });
    transcriber.ErrorReceived.Subscribe(error => Console.WriteLine($"Real-time error: {error.Error}"));
    transcriber.Closed.Subscribe(closeEvent =>
     Console.WriteLine("Real-time connection closed: {0} - {1}",
         closeEvent.Code,
         closeEvent.Reason
     )
    );
    ```

    The real-time transcriber returns two types of transcripts: *partial* and *final*.

    * *Partial transcripts* are returned as the audio is being streamed to AssemblyAI.
    * *Final transcripts* are returned when the service detects a pause in speech.

    <Tip>
      You can [configure the silence threshold](/docs/speech-to-text/streaming#configure-the-threshold-for-automatic-utterance-detection) for automatic utterance detection and programmatically [force the end of an utterance](/docs/speech-to-text/streaming#manually-end-current-utterance) to immediately get a *Final transcript*.
    </Tip>
  </Step>
</Steps>

## Step 4: Connect the streaming service

Streaming Speech-to-Text uses [WebSockets](https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API) to stream audio to AssemblyAI. This requires first establishing a connection to the API.

```csharp theme={"system"}
Console.WriteLine("Connecting to real-time transcript service");await transcriber.ConnectAsync();
```

## Step 5: Record audio from microphone

In this step, you'll use [SoX](http://sox.sourceforge.net/), a cross-platform audio library, to record audio from your microphone.

<Steps>
  <Step>
    Install SoX on your machine.

    <CodeGroup>
      ```bash macOs theme={"system"}
      brew install sox
      ```

      ```bash Windows theme={"system"}
      Download the SoX binaries and add the sox executable to your PATH.
      ```

      ```bash Linux theme={"system"}
      apt-get install sox libsox-fmt-all
      ```
    </CodeGroup>
  </Step>

  <Step>
    To run the SoX process and pipe the audio data to the process output, add the following code:

    ```csharp theme={"system"}
    Console.WriteLine("Starting recording");

    var soxArguments = string.Join(' ', [
     // --default-device doesn't work on Windows
     RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "-t waveaudio default" : "--default-device",
     "--no-show-progress",
     $"--rate {sampleRate}",
     "--channels 1",
     "--encoding signed-integer",
     "--bits 16",
     "--type wav",
     "-" // pipe
    ]);
    using var soxProcess = new Process
    {
     StartInfo = new ProcessStartInfo
     {
         FileName = "sox",
         Arguments = soxArguments,
         RedirectStandardOutput = true,
         UseShellExecute = false,
         CreateNoWindow = true
     }
    };

    soxProcess.Start();
    ```

    <Note>
      The SoX arguments configure the format of the audio output. The arguments configure the format to a single channel with 16-bit signed integer PCM encoding and 16 kHz sample rate.

      If you want to stream data from elsewhere, make sure that your audio data is in the following format:

      * Single channel
      * 16-bit signed integer PCM or mu-law encoding

      By default, the Streaming STT service expects PCM16-encoded audio. If you want to use mu-law encoding, see [Specifying the encoding](/docs/guides/real-time-streaming-transcription#specifying-the-encoding).
    </Note>
  </Step>

  <Step>
    Read the audio data from the SoX process output and send it to the real-time transcriber.

    ```csharp theme={"system"}
    var soxOutputStream = soxProcess.StandardOutput.BaseStream;
    var buffer = new byte[4096];
    while (await soxOutputStream.ReadAsync(buffer, 0, buffer.Length, ct) > 0)
    {
     if (ct.IsCancellationRequested) break;
     await transcriber.SendAudioAsync(buffer);
    }
    ```
  </Step>
</Steps>

## Step 6: Disconnect the real-time service

When you are done, stop the recording, and disconnect the transcriber to close the connection.

```csharp theme={"system"}
soxProcess.Kill();await transcriber.CloseAsync();
```

## Next steps

To learn more about Streaming Speech-to-Text, see the following resources:

* [Streaming Speech-to-Text](/docs/speech-to-text/streaming)
* [Streaming STT WebSocket API reference](/docs/api-reference/streaming)

## Need some help?

If you get stuck, or have any other questions, we'd love to help you out. Ask our support team in our [Discord server](https://discord.gg/aSMMpMadFh).