C# Live Streaming: Build Your Own OBS With FFmpeg

Aug 6, 2025 by Sebastian Müller 50 views

C# Screen and Audio Broadcasting to Another Application Like OBS

Introduction

Hey guys! Ever wondered how you can build your own screen and audio broadcasting application in C#, just like OBS? It's a pretty cool project, and in this article, we're going to dive deep into the libraries and techniques you can use to achieve this. We'll cover everything from capturing your screen and audio to streaming it to platforms like YouTube and Twitch, complete with all the bells and whistles like quality settings, audio adjustments, resolution controls, and bitrate management. So, buckle up and let's get started!

Understanding the Basics of Screen and Audio Broadcasting

Before we jump into the code, let's break down the fundamental concepts behind screen and audio broadcasting. At its core, broadcasting involves capturing your screen and audio, encoding it into a streamable format, and then transmitting that stream to a server. This server then distributes the stream to viewers across the internet. Think of it like a live TV broadcast, but instead of using traditional TV infrastructure, we're leveraging the power of the internet.

Screen capturing is the process of grabbing frames from your display. This can be done using various APIs provided by the operating system. For example, in Windows, you can use the Desktop Duplication API or the BitBlt function. Each method has its pros and cons, with some being more efficient and others offering better compatibility.

Audio capturing involves recording the audio output from your system or a specific microphone. This can be achieved using APIs like NAudio in C#, which provides a high-level interface for audio recording and playback.

Encoding is the process of converting the captured screen and audio data into a format suitable for streaming. This typically involves compressing the data to reduce its size and encoding it using a codec like H.264 for video and AAC for audio. The choice of codec and encoding settings (such as bitrate and resolution) significantly impacts the quality and bandwidth requirements of the stream.

Streaming is the process of transmitting the encoded data to a server. This is usually done using protocols like RTMP (Real-Time Messaging Protocol) or newer alternatives like SRT (Secure Reliable Transport). The server then redistributes the stream to viewers, often using protocols like HLS (HTTP Live Streaming) or DASH (Dynamic Adaptive Streaming over HTTP).

Exploring Libraries for Screen and Audio Broadcasting in C#

Now that we have a solid understanding of the basics, let's explore some of the libraries available in C# that can help us build our broadcasting application. There are several options, each with its own strengths and weaknesses.

1. FFmpeg

FFmpeg is a powerhouse when it comes to multimedia processing. It's not just a library; it's a complete, cross-platform solution for recording, converting, and streaming audio and video. While FFmpeg is written in C, there are several C# wrappers available that make it easier to use in your .NET projects. These wrappers provide a managed interface to FFmpeg's functionality, allowing you to leverage its capabilities without having to deal with the complexities of native code directly.

Why is FFmpeg so popular? Well, it supports a vast array of codecs, formats, and protocols. Whether you're working with H.264, H.265, VP9, or any other codec, FFmpeg has you covered. It also supports various streaming protocols like RTMP, HLS, and DASH, making it a versatile choice for building broadcasting applications. Plus, it's highly configurable, allowing you to fine-tune every aspect of the encoding and streaming process.

However, FFmpeg's power comes with a bit of complexity. It has a steep learning curve, and using it effectively requires a good understanding of multimedia concepts. The command-line interface can be intimidating at first, but once you get the hang of it, you'll appreciate its flexibility and control. The C# wrappers help to simplify things, but you'll still need to understand FFmpeg's underlying principles to get the most out of it.

2. NAudio

NAudio is a fantastic library for audio processing in C#. It provides a comprehensive set of tools for recording, playing, and manipulating audio. While NAudio doesn't handle video, it's an essential component for any application that needs to capture or process audio, including our broadcasting application. It's super user-friendly, making it a great choice for both beginners and experienced developers.

With NAudio, you can easily capture audio from various sources, such as microphones or the system's audio output. It supports various audio formats and codecs, allowing you to encode the captured audio in the format of your choice. NAudio also provides features for audio mixing, effects processing, and playback, making it a versatile tool for all your audio needs.

One of the great things about NAudio is its clear and well-documented API. The library is designed to be easy to use, with a wealth of examples and tutorials available online. Whether you're recording audio, applying effects, or streaming audio data, NAudio provides a straightforward and efficient solution.

3. DirectShow.NET

DirectShow.NET is a C# wrapper for the DirectShow API, a multimedia framework developed by Microsoft. DirectShow provides a powerful and flexible way to capture, process, and render audio and video. It's a lower-level API than FFmpeg, but it offers a high degree of control over the multimedia pipeline. If you're looking for a granular level of control over your broadcasting application, DirectShow.NET might be the way to go. It gives you the tools to create complex filter graphs for capturing, encoding, and streaming media.

One of the advantages of DirectShow is its support for a wide range of hardware devices. It can work with webcams, capture cards, and other multimedia devices, allowing you to build applications that capture video from various sources. DirectShow also supports various codecs and formats, making it a versatile choice for multimedia processing.

However, DirectShow can be challenging to use due to its complexity. Building a DirectShow filter graph requires a good understanding of the API and the underlying multimedia concepts. DirectShow.NET simplifies things somewhat, but it's still a more advanced option compared to FFmpeg or NAudio. If you're willing to invest the time to learn it, DirectShow can provide you with a powerful and flexible solution for screen and audio broadcasting.

Implementing Screen and Audio Capture

Okay, let's get our hands dirty with some code! We'll start by implementing the screen and audio capture functionality. For screen capture, we'll use the Graphics.CopyFromScreen method, which is a simple and effective way to grab frames from the screen. For audio capture, we'll use NAudio, which provides a straightforward API for recording audio.

Screen Capture

Here's a basic example of how to capture the screen using Graphics.CopyFromScreen:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Threading;

public class ScreenCapture
{
 public static void CaptureScreen(string filePath)
 {
 Size screenSize = new Size(
 System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width,
 System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height
 );
 using (Bitmap bitmap = new Bitmap(screenSize.Width, screenSize.Height))
 {
 using (Graphics graphics = Graphics.FromImage(bitmap))
 {
 graphics.CopyFromScreen(Point.Empty, Point.Empty, screenSize);
 }
 bitmap.Save(filePath, ImageFormat.Png);
 }
 }

 public static void Main(string[] args)
 {
 CaptureScreen("screen.png");
 }
}

This code captures the entire screen and saves it as a PNG image. You can modify this code to capture specific regions of the screen or to capture frames at a specific rate for video recording.

Audio Capture

Now, let's capture some audio using NAudio. Here's a basic example:

using NAudio.Wave;
using System;

public class AudioCapture
{
 public static void CaptureAudio(string filePath)
 {
 int waveInDevices = WaveIn.DeviceCount;
 if (waveInDevices == 0)
 {
 Console.WriteLine("No audio input devices found.");
 return;
 }

 WaveInCapabilities deviceInfo = WaveIn.GetCapabilities(0);
 Console.WriteLine("Selected device: {0}", deviceInfo.ProductName);

 WaveIn waveIn = new WaveIn
 {
 WaveFormat = new WaveFormat(44100, 1),
 DeviceNumber = 0 // Use the first audio input device
 };

 WaveFileWriter waveFileWriter = new WaveFileWriter(filePath, waveIn.WaveFormat);

 waveIn.DataAvailable += (sender, e) =>
 {
 waveFileWriter.Write(e.Buffer, 0, e.BytesRecorded);
 };

 waveIn.RecordingStopped += (sender, e) =>
 {
 waveFileWriter.Dispose();
 waveIn.Dispose();
 };

 waveIn.StartRecording();

 Console.WriteLine("Recording audio...");
 Console.ReadKey();
 waveIn.StopRecording();
 Console.WriteLine("Audio recording finished.");
 }

 public static void Main(string[] args)
 {
 CaptureAudio("audio.wav");
 }
}

This code captures audio from the default input device and saves it as a WAV file. You can adjust the audio format, device number, and other settings to suit your needs.

Encoding and Streaming with FFmpeg

With screen and audio capture in place, the next step is to encode the captured data and stream it to a server. This is where FFmpeg comes in. As we discussed earlier, FFmpeg is a powerful tool for encoding and streaming multimedia data. We'll use a C# wrapper for FFmpeg to simplify the process.

Setting up FFmpeg

First, you'll need to install FFmpeg on your system and add the FFmpeg C# wrapper to your project. There are several wrappers available, such as FFmpeg.AutoGen and NReco.VideoConverter. For this example, we'll use NReco.VideoConverter, which provides a high-level API for FFmpeg.

Encoding and Streaming

Here's an example of how to use NReco.VideoConverter to encode screen and audio and stream it to an RTMP server:

using NReco.VideoConverter;
using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Threading;

public class Streaming
{
 public static void StreamScreenAndAudio(string rtmpUrl)
 {
 var ffMpeg = new NReco.VideoConverter.FFMpegConverter();
 var videoSettings = new VideoStreamSettings
 {
 Width = 1280,
 Height = 720,
 FrameRate = 30,
 BitRate = 2000 * 1000, // 2 Mbps
 Codec = "libx264"
 };
 var audioSettings = new AudioStreamSettings
 {
 SampleRate = 44100,
 BitRate = 128 * 1000, // 128 Kbps
 Codec = "aac"
 };

 // Create a named pipe for video input
 string videoPipeName = @"\\.\pipe\screen_pipe";
 if (File.Exists(videoPipeName)) {
 File.Delete(videoPipeName);
 }
 NamedPipeServerStream videoPipeServer = new NamedPipeServerStream("screen_pipe", PipeDirection.Out);
 // Create a named pipe for audio input
 string audioPipeName = @"\\.\pipe\audio_pipe";
 if (File.Exists(audioPipeName)) {
 File.Delete(audioPipeName);
 }
 NamedPipeServerStream audioPipeServer = new NamedPipeServerStream("audio_pipe", PipeDirection.Out);

 Console.WriteLine("Waiting for video pipe client...");
 videoPipeServer.WaitForConnection();
 Console.WriteLine("Video pipe connected.");
 Console.WriteLine("Waiting for audio pipe client...");
 audioPipeServer.WaitForConnection();
 Console.WriteLine("Audio pipe connected.");

 Thread captureThread = new Thread(() => {
 try {
 Size screenSize = new Size(
 System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width,
 System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height
 );
 while (true)
 {
 using (Bitmap bitmap = new Bitmap(screenSize.Width, screenSize.Height, PixelFormat.Format32bppRgb))
 {
 using (Graphics graphics = Graphics.FromImage(bitmap))
 {
 graphics.CopyFromScreen(Point.Empty, Point.Empty, screenSize);
 }
 var ms = new MemoryStream();
 bitmap.Save(ms, ImageFormat.Png); // Or use Jpeg, make sure FFMpeg input setting is the same
 ms.WriteTo(videoPipeServer);
 }
 Thread.Sleep(1000 / videoSettings.FrameRate);
 }
 }
 catch (Exception ex) {
 Console.WriteLine("Capture Thread Exception: " + ex.Message);
 }
 finally {
 videoPipeServer.Close();
 }
 });
 captureThread.Start();

 Thread audioCaptureThread = new Thread(() => {
 try {
 using (var waveIn = new WaveIn
 {
 WaveFormat = new WaveFormat(audioSettings.SampleRate, 1),
 DeviceNumber = 0
 })
 {
 byte[] buffer = new byte[waveIn.WaveFormat.AverageBytesPerSecond * 1]; // 1 second buffer
 while (true)
 {
 int bytesRead = waveIn.Read(buffer, 0, buffer.Length);
 if (bytesRead > 0)
 {
 audioPipeServer.Write(buffer, 0, bytesRead);
 }
 else
 {
 Thread.Sleep(10);
 }
 }
 }
 }
 catch (Exception ex) {
 Console.WriteLine("Audio Capture Thread Exception: " + ex.Message);
 }
 finally {
 audioPipeServer.Close();
 }
 });
 audioCaptureThread.Start();

 string inputVideoPipe = "\\\\.\\pipe\\screen_pipe"; // need double backslashes in C#
 string inputAudioPipe = "\\\\.\\pipe\\audio_pipe";

 ffMpeg.ConvertLiveMediaStream(new ConvertLiveMediaStreamInput
 {
 Video = new LiveMediaStreamInputSettings { StreamPath = inputVideoPipe, Format = "image2pipe", VideoFrameSize = new Size(videoSettings.Width, videoSettings.Height), CustomInputArgs = "-f image2pipe -framerate " + videoSettings.FrameRate },
 Audio = new LiveMediaStreamInputSettings { StreamPath = inputAudioPipe, Format = "s16le", SampleRate = audioSettings.SampleRate, Channels = 1 },
 }, null, new ConvertLiveMediaStreamOutput
 {
 StreamPath = rtmpUrl,
 Format = "flv", // RTMP output is always FLV
 Video = videoSettings,
 Audio = audioSettings
 });

 Console.WriteLine("Streaming finished.");
 captureThread.Join();
 audioCaptureThread.Join();
 }

 public static void Main(string[] args)
 {
 // Replace with your RTMP URL
 string rtmpUrl = "rtmp://your-rtmp-server/live/your-stream-key";
 StreamScreenAndAudio(rtmpUrl);
 }
}

This code sets up video and audio settings, captures the screen and audio, and streams it to the specified RTMP URL. You'll need to replace "rtmp://your-rtmp-server/live/your-stream-key" with your actual RTMP URL.

Advanced Features and Customization

Now that you have a basic broadcasting application, you can start adding advanced features and customization options. Here are a few ideas:

Quality Settings

Allow users to adjust the quality of the stream by changing the resolution, bitrate, and frame rate. This can be done by modifying the VideoStreamSettings and AudioStreamSettings in the FFmpeg code.

Audio Input Selection

Let users select their audio input device. You can use NAudio to enumerate the available audio devices and allow the user to choose one.

Overlay Graphics

Add overlay graphics, such as a logo or a webcam feed, to the stream. This can be done by manipulating the captured screen frames or by using FFmpeg's overlay filter.

Chat Integration

Integrate with chat platforms like Twitch or YouTube Chat to display chat messages on the stream. This can be done using the respective platform's APIs.

Conclusion

Building a screen and audio broadcasting application in C# is a challenging but rewarding project. By leveraging libraries like FFmpeg and NAudio, you can create a powerful and customizable broadcasting solution. We've covered the basics of screen and audio capture, encoding, and streaming, and we've explored some advanced features and customization options. Now it's your turn to get creative and build your own broadcasting masterpiece! Remember, the key is to experiment, learn, and have fun. Happy coding, guys!