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How to Build Membrane WebRTC App with Elixir?

Learn how to build high-performance real-time communication applications using Membrane WebRTC with Elixir and C++.

Introduction to Membrane WebRTC Technology

What is Membrane WebRTC?

Membrane WebRTC is an advanced multimedia processing framework designed to facilitate real-time communication over the internet. Built on the robust and scalable Elixir programming language, Membrane WebRTC stands out for its efficiency and flexibility in handling complex multimedia tasks such as streaming, transcoding, and selective forwarding. By leveraging the power of Elixir and integrating with C++, this framework offers developers a powerful tool to create high-performance applications for video conferencing, live broadcasting, and other real-time communication solutions.

Key Features of Membrane WebRTC

Membrane WebRTC offers a range of features that make it a preferred choice for developers looking to implement real-time communication capabilities. Some of the key features include:
  • Scalability and Performance: Thanks to Elixir's concurrency model and the integration with C++, Membrane WebRTC can handle numerous simultaneous connections and data streams with low latency, making it ideal for large-scale applications.
  • Modular Architecture: Membrane’s pipeline-based architecture allows for easy customization and extension, enabling developers to create tailored solutions by assembling various components.
  • Advanced Processing Capabilities: The framework supports complex multimedia operations like transcoding and media format conversion, providing high flexibility in managing different types of media streams.
  • Selective Forwarding Unit (SFU): Membrane WebRTC includes an SFU, which optimizes bandwidth usage by only forwarding the necessary media streams to each participant, significantly enhancing performance and reducing resource consumption.
Membrane WebRTC's combination of these features positions it as a leading solution for developers aiming to build robust and scalable real-time communication applications.

Getting Started with the Code!

Create a New Membrane WebRTC App

To get started with Membrane WebRTC, the first step is to create a new application. Begin by setting up a new Elixir project. Open your terminal and run the following commands:

bash

1mix new membrane_webrtc_app --module MembraneWebrtcApp
2cd membrane_webrtc_app
This will create a new directory for your project and initialize it with a basic Elixir application structure.

Install Necessary Dependencies

Next, you need to install the necessary dependencies for working with Membrane WebRTC. Add the following lines to your mix.exs file within the defp deps do section:

Elixir

1defp deps do
2  [
3    {:membrane_core, "~> 0.7.0"},
4    {:membrane_webrtc_plugin, "~> 0.6.0"},
5    {:membrane_element_file, "~> 0.5.0"}
6  ]
7end
After updating the mix.exs file, run the following command to fetch and install the dependencies:

bash

1mix deps.get

Structure of the Project

Understanding the structure of your project is crucial for efficient development. Here’s a brief overview of the key directories and files:
  • lib/: Contains the source code of your application.
  • config/: Configuration files for your application.
  • test/: Test files for your application.
Your main development work will be in the lib/ directory, where you'll define modules and functions for your Membrane WebRTC application.

App Architecture

membrane-webrtc
The architecture of a Membrane WebRTC application revolves around pipelines and elements. Here’s a high-level overview:
  • Pipelines: These are responsible for managing the flow of data through various elements.
  • Elements: These are individual components that perform specific tasks, such as encoding, decoding, or forwarding media streams.
In Membrane, pipelines are constructed by connecting elements in a specific sequence to achieve the desired processing workflow. This modular approach allows for easy scalability and customization.
To give you a concrete example, your application might have a pipeline that receives media from a WebRTC source, processes it through a series of elements for tasks like encoding or mixing, and then sends it out to connected clients.
By understanding and setting up this basic architecture, you lay the groundwork for developing more complex and functional WebRTC applications with Membrane.

Step 1: Get Started with Configuration

Setting Up the Environment

Before diving into coding, it's essential to set up the environment correctly. This includes configuring your development tools and setting up necessary environment variables. Ensure you have Elixir and Erlang installed on your system. You can install Elixir by following the official installation guide:

Elixir Installation Guide

.
After installing Elixir, navigate to your project directory and create a .env file to store environment variables required for your application. Open the terminal and run:

bash

1touch .env
Edit the .env file to include any necessary configurations, such as database URLs or API keys. Here’s an example of what your .env file might look like:

env

1DATABASE_URL=postgres://user:password@localhost/membrane_webrtc_db
2SECRET_KEY_BASE=your_secret_key_base
To load these variables into your application, add the dotenv library to your project. Update your mix.exs file:

Elixir

1defp deps do
2  [
3    {:dotenv, "~> 3.0"}
4  ]
5end
Then fetch the new dependency:

bash

1mix deps.get
And load the environment variables at the start of your application by adding this line to your config/config.exs:

Elixir

1Dotenv.load

Initializing the Project

With your environment set up, you can now initialize your Membrane WebRTC project. Start by creating a new module for your WebRTC pipeline. Create a new file lib/membrane_webrtc_app/pipeline.ex:

bash

1mkdir -p lib/membrane_webrtc_app
2touch lib/membrane_webrtc_app/pipeline.ex
Open pipeline.ex and define a basic Membrane pipeline:

Elixir

1defmodule MembraneWebrtcApp.Pipeline do
2  use Membrane.Pipeline
3
4  @impl true
5  def handle_init(_opts) do
6    spec = %Membrane.ParentSpec{
7      children: [
8        # Add children elements here
9      ]
10    }
11
12    {{:ok, spec}, %{}}
13  end
14end
Next, configure your application to start this pipeline. Open lib/membrane_webrtc_app/application.ex and update it to start the pipeline:

Ellixir

1defmodule MembraneWebrtcApp.Application do
2  use Application
3
4  @impl true
5  def start(_type, _args) do
6    children = [
7      MembraneWebrtcApp.Pipeline
8    ]
9
10    opts = [strategy: :one_for_one, name: MembraneWebrtcApp.Supervisor]
11    Supervisor.start_link(children, opts)
12  end
13end
In your config/config.exs, add configuration for your pipeline:

Elixir

1config :membrane_webrtc_app, MembraneWebrtcApp.Pipeline, [
2  # Add pipeline specific configurations here
3]
Now, your project is initialized with the basic setup to start building your Membrane WebRTC application. This configuration ensures your environment is ready and your application is set up to run the WebRTC pipeline as soon as you start it.

Step 2: Wireframe All the Components

Designing the Wireframe

Before diving into the implementation, it's crucial to have a clear wireframe of all the components your Membrane WebRTC application will have. A wireframe helps visualize the structure and interaction between different parts of the application. Here’s a simple wireframe for a basic WebRTC application:

Join Screen

  • Input fields for username and room ID
  • Join button

Main Screen

  • Video display area for local and remote video streams
  • Control buttons (mute/unmute, video on/off, hang up)
  • List of participants

Backend Components

  • WebRTC signaling server
  • Media pipeline for processing audio and video streams

Implementing the Wireframe

With the wireframe in place, let's start implementing these components. We'll begin by setting up the join screen, which is the entry point for users to enter the application.

[a] Join Screen

Create a new file lib/membrane_webrtc_app_web/live/join_live.ex and define a LiveView module to handle the join screen:

Elixir

1defmodule MembraneWebrtcAppWeb.JoinLive do
2  use MembraneWebrtcAppWeb, :live_view
3
4  def mount(_params, _session, socket) do
5    {:ok, assign(socket, username: "", room_id: "")}
6  end
7
8  def handle_event("join", %{"username" => username, "room_id" => room_id}, socket) do
9    {:noreply, push_redirect(socket, to: Routes.live_path(socket, MembraneWebrtcAppWeb.RoomLive, room_id, username))}
10  end
11end
Create a corresponding template file lib/membrane_webrtc_app_web/templates/live/join_live.html.leex for the join screen:

HTML

1<div>
2  <h1>Join a Room</h1>
3  <form phx-submit="join">
4    <label for="username">Username:</label>
5    <input type="text" id="username" name="username" value="<%= @username %>"/>
6    
7    <label for="room_id">Room ID:</label>
8    <input type="text" id="room_id" name="room_id" value="<%= @room_id %>"/>
9    
10    <button type="submit">Join</button>
11  </form>
12</div>
This code sets up a basic join screen where users can input their username and room ID to join a WebRTC session.

[b] Main Screen

Next, let's create the main screen where the video and controls will be displayed. Create a new LiveView module lib/membrane_webrtc_app_web/live/room_live.ex:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomLive do
2  use MembraneWebrtcAppWeb, :live_view
3
4  def mount(%{"room_id" => room_id, "username" => username}, _session, socket) do
5    {:ok, assign(socket, room_id: room_id, username: username, video_streams: [])}
6  end
7
8  def handle_event("mute", _params, socket) do
9    # Handle mute/unmute logic here
10    {:noreply, socket}
11  end
12
13  def handle_event("toggle_video", _params, socket) do
14    # Handle video on/off logic here
15    {:noreply, socket}
16  end
17end
Create a corresponding template file lib/membrane_webrtc_app_web/templates/live/room_live.html.leex for the main screen:

HTML

1<div>
2  <h1>Room: <%= @room_id %></h1>
3  <div id="video-streams">
4    <%= for stream <- @video_streams do %>
5      <video id="<%= stream.id %>" autoplay></video>
6    <% end %>
7  </div>
8  <div id="controls">
9    <button phx-click="mute">Mute/Unmute</button>
10    <button phx-click="toggle_video">Video On/Off</button>
11    <button phx-click="hang_up">Hang Up</button>
12  </div>
13  <div id="participants">
14    <h2>Participants</h2>
15    <!-- List participants here -->
16  </div>
17</div>
This main screen template includes areas for displaying video streams, control buttons for muting, toggling video, and hanging up, as well as a section for listing participants.

[c] Backend Components

Finally, set up the WebRTC signaling server and media pipeline. The signaling server will manage the communication between clients, while the media pipeline will handle the actual processing of audio and video streams.
For the signaling server, you might use Phoenix Channels. Add the following to your lib/membrane_webrtc_app_web/channels/user_socket.ex:

Elixir

1defmodule MembraneWebrtcAppWeb.UserSocket do
2  use Phoenix.Socket
3
4  ## Channels
5  channel "room:*", MembraneWebrtcAppWeb.RoomChannel
6
7  # Socket params are passed from the client and can
8  # be used to verify and authenticate a user. After
9  # verification, you can put default assigns into
10  # the socket that will be set for all channels, ie
11  # socket.assigns[:user_id]. To deny connection, return
12  # `:error`.
13  #
14  # See `Phoenix.Token` documentation for examples in
15  # performing token verification on connect.
16  @impl true
17  def connect(_params, socket, _connect_info) do
18    {:ok, socket}
19  end
20
21  @impl true
22  def id(_socket), do: nil
23end
And create the room channel in lib/membrane_webrtc_app_web/channels/room_channel.ex:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomChannel do
2  use MembraneWebrtcAppWeb, :channel
3
4  def join("room:" <> _room_id, _payload, socket) do
5    {:ok, socket}
6  end
7
8  def handle_in("new_peer", %{"peer_id" => peer_id}, socket) do
9    # Handle new peer joining the room
10    {:reply, :ok, socket}
11  end
12end
This channel will manage the WebRTC signaling messages between clients.

Step 3: Implement Join Screen

User Interface for Join Screen

The join screen is the entry point for users to connect to your Membrane WebRTC application. It includes fields for the user to enter their username and room ID, as well as a button to join the room. We have already set up the basic structure in the wireframe. Now, let's enhance it with more details and functionality.
First, ensure that the JoinLive module handles user input effectively. Update the join_live.ex file to include more user interaction handling:

Elixir

1defmodule MembraneWebrtcAppWeb.JoinLive do
2  use MembraneWebrtcAppWeb, :live_view
3
4  def mount(_params, _session, socket) do
5    {:ok, assign(socket, username: "", room_id: "")}
6  end
7
8  def handle_event("validate", %{"join" => join_params}, socket) do
9    {:noreply, assign(socket, join_params)}
10  end
11
12  def handle_event("join", %{"join" => %{"username" => username, "room_id" => room_id}}, socket) do
13    if username != "" and room_id != "" do
14      {:noreply, push_redirect(socket, to: Routes.room_path(socket, :index, room_id, username))}
15    else
16      {:noreply, socket |> put_flash(:error, "Both fields are required.") |> assign(:username, username) |> assign(:room_id, room_id)}
17    end
18  end
19end
In this module, we added an event handler for validate to dynamically update the state of the form fields. We also updated the join event handler to include validation logic, ensuring that both the username and room ID are provided before redirecting the user to the room.
Next, update the corresponding template join_live.html.leex to handle the new validation and display any error messages:

HTML

1<div>
2  <h1>Join a Room</h1>
3  <%= if @flash[:error] do %>
4    <div class="alert alert-danger"><%= @flash[:error] %></div>
5  <% end %>
6  <form phx-change="validate" phx-submit="join">
7    <div>
8      <label for="username">Username:</label>
9      <input type="text" id="username" name="join[username]" value="<%= @username %>" required />
10    </div>
11    <div>
12      <label for="room_id">Room ID:</label>
13      <input type="text" id="room_id" name="join[room_id]" value="<%= @room_id %>" required />
14    </div>
15    <div>
16      <button type="submit">Join</button>
17    </div>
18  </form>
19</div>
This HTML template includes the form with phx-change and phx-submit events bound to our LiveView module's event handlers. It also displays error messages when necessary.

Backend Logic for Join Screen

The backend logic for the join screen involves setting up routing and handling the join requests effectively. Ensure that your router is configured to handle the join path and redirect to the room.
In your router.ex file, update the routing to include paths for joining and rooms:

Elixir

1defmodule MembraneWebrtcAppWeb.Router do
2  use MembraneWebrtcAppWeb, :router
3
4  pipeline :browser do
5    plug :accepts, ["html"]
6    plug :fetch_session
7    plug :fetch_flash
8    plug :protect_from_forgery
9    plug :put_secure_browser_headers
10  end
11
12  pipeline :api do
13    plug :accepts, ["json"]
14  end
15
16  scope "/", MembraneWebrtcAppWeb do
17    pipe_through :browser
18
19    live "/", JoinLive, :index
20    live "/room/:room_id/:username", RoomLive, :index
21  end
22
23  # Other scopes may use custom stacks.
24  # scope "/api", MembraneWebrtcAppWeb do
25  #   pipe_through :api
26  # end
27end
This routing configuration sets up the root path to display the join screen and dynamically handles the room and username parameters for the room path.
By implementing these steps, we now have a fully functional join screen that collects user input and validates it before allowing users to join a WebRTC room. This setup ensures a smooth user experience and robust backend handling for joining sessions.

Step 4: Implement Controls

Adding Control Features

Control features are essential for any WebRTC application, allowing users to manage their audio and video settings during a call. We will implement basic controls such as mute/unmute, video on/off, and hang up. These controls will interact with the WebRTC backend to manage the media streams.
First, let's enhance the RoomLive module to include these controls. Open lib/membrane_webrtc_app_web/live/room_live.ex and update it with event handlers for the control actions:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomLive do
2  use MembraneWebrtcAppWeb, :live_view
3
4  def mount(%{"room_id" => room_id, "username" => username}, _session, socket) do
5    {:ok, assign(socket, room_id: room_id, username: username, muted: false, video_off: false, participants: [])}
6  end
7
8  def handle_event("mute", _params, socket) do
9    muted = !socket.assigns.muted
10    # Here you would add the logic to actually mute the audio stream
11    {:noreply, assign(socket, muted: muted)}
12  end
13
14  def handle_event("toggle_video", _params, socket) do
15    video_off = !socket.assigns.video_off
16    # Here you would add the logic to actually turn the video on/off
17    {:noreply, assign(socket, video_off: video_off)}
18  end
19
20  def handle_event("hang_up", _params, socket) do
21    # Here you would add the logic to disconnect from the WebRTC session
22    {:noreply, push_redirect(socket, to: Routes.page_path(socket, :index))}
23  end
24end
This module now includes handlers for muting the audio, toggling the video, and hanging up the call. These handlers update the socket's assigns and can be expanded to include the actual logic for interacting with the media streams.
Next, update the template for the main screen to include buttons for these controls. Open lib/membrane_webrtc_app_web/templates/live/room_live.html.leex:

HTML

1<div>
2  <h1>Room: <%= @room_id %></h1>
3  <div id="video-streams">
4    <%= for participant <- @participants do %>
5      <video id="<%= participant.id %>" autoplay></video>
6    <% end %>
7  </div>
8  <div id="controls">
9    <button phx-click="mute"><%= if @muted, do: "Unmute", else: "Mute" %></button>
10    <button phx-click="toggle_video"><%= if @video_off, do: "Video On", else: "Video Off" %></button>
11    <button phx-click="hang_up">Hang Up</button>
12  </div>
13  <div id="participants">
14    <h2>Participants</h2>
15    <ul>
16      <%= for participant <- @participants do %>
17        <li><%= participant.username %></li>
18      <% end %>
19    </ul>
20  </div>
21</div>
This template includes buttons that trigger the corresponding events defined in the RoomLive module. The button labels dynamically change based on the current state (e.g., "Mute" changes to "Unmute" when the user is muted).

Integrating Controls with Backend

To make these controls functional, you need to integrate them with the WebRTC backend. This involves managing media streams and signaling.

[a] Handling Media Streams

In your RoomChannel module, you can handle the mute and video toggle actions by interacting with the WebRTC API. Update lib/membrane_webrtc_app_web/channels/room_channel.ex to include logic for these controls:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomChannel do
2  use MembraneWebrtcAppWeb, :channel
3
4  def join("room:" <> _room_id, _payload, socket) do
5    {:ok, socket}
6  end
7
8  def handle_in("mute", %{"peer_id" => peer_id}, socket) do
9    # Logic to mute the peer's audio stream
10    {:reply, :ok, socket}
11  end
12
13  def handle_in("toggle_video", %{"peer_id" => peer_id}, socket) do
14    # Logic to turn on/off the peer's video stream
15    {:reply, :ok, socket}
16  end
17
18  def handle_in("hang_up", %{"peer_id" => peer_id}, socket) do
19    # Logic to disconnect the peer
20    {:reply, :ok, socket}
21  end
22end
These handlers will manage the signaling for muting, toggling video, and hanging up. You will need to implement the actual logic to interact with the WebRTC API in your client-side JavaScript.

[b] Client-Side JavaScript

In your client-side code, handle the WebRTC actions using the appropriate WebRTC API calls. Create a new JavaScript file assets/js/room.js and include logic to manage media streams:

JavaScript

1let localStream;
2
3async function getUserMedia() {
4  localStream = await navigator.mediaDevices.getUserMedia({ video: true, audio: true });
5  document.querySelector('#localVideo').srcObject = localStream;
6}
7
8function toggleMute() {
9  localStream.getAudioTracks().forEach(track => track.enabled = !track.enabled);
10}
11
12function toggleVideo() {
13  localStream.getVideoTracks().forEach(track => track.enabled = !track.enabled);
14}
15
16document.querySelector('#muteButton').addEventListener('click', toggleMute);
17document.querySelector('#videoButton').addEventListener('click', toggleVideo);
18document.querySelector('#hangUpButton').addEventListener('click', () => {
19  localStream.getTracks().forEach(track => track.stop());
20  // Additional logic to leave the room and close connections
21});
22
23getUserMedia();
In your HTML template, include the video element and buttons for the controls:

HTML

1<video id="localVideo" autoplay></video>
2<button id="muteButton">Mute</button>
3<button id="videoButton">Video Off</button>
4<button id="hangUpButton">Hang Up</button>
This JavaScript code captures the local media stream and provides functions to toggle the audio and video tracks, implementing the mute and video toggle features. The hang-up button stops all media tracks and handles leaving the room.
By implementing these control features, users can effectively manage their audio and video settings during a WebRTC session, enhancing the overall user experience. In the next part, we'll focus on displaying and managing participants' views.

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Step 5: Implement Participant View

Displaying Participants

Displaying participants in a WebRTC session is crucial for a collaborative and interactive experience. Each participant's video stream should be visible to others in the room. We will enhance our RoomLive module and template to manage and display these streams effectively.
First, update the RoomLive module to handle participants joining and leaving, as well as managing their video streams. Open lib/membrane_webrtc_app_web/live/room_live.ex:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomLive do
2  use MembraneWebrtcAppWeb, :live_view
3
4  def mount(%{"room_id" => room_id, "username" => username}, _session, socket) do
5    if connected?(socket) do
6      MembraneWebrtcAppWeb.Endpoint.subscribe("room:#{room_id}")
7    end
8
9    {:ok, assign(socket, room_id: room_id, username: username, muted: false, video_off: false, participants: [])}
10  end
11
12  def handle_info(%{event: "new_peer", payload: %{peer_id: peer_id, username: username}}, socket) do
13    participants = [%{id: peer_id, username: username} | socket.assigns.participants]
14    {:noreply, assign(socket, participants: participants)}
15  end
16
17  def handle_info(%{event: "peer_left", payload: %{peer_id: peer_id}}, socket) do
18    participants = Enum.reject(socket.assigns.participants, fn p -> p.id == peer_id end)
19    {:noreply, assign(socket, participants: participants)}
20  end
21
22  # ... other handle_event functions for mute, toggle_video, hang_up
23
24end
Here, we subscribe to the room:#{room_id} topic to receive notifications when new peers join or leave the room. The handle_info/2 functions manage the participants list accordingly.
Next, update the RoomChannel to broadcast these events. Open lib/membrane_webrtc_app_web/channels/room_channel.ex:

Elixir

1defmodule MembraneWebrtcAppWeb.RoomChannel do
2  use MembraneWebrtcAppWeb, :channel
3
4  def join("room:" <> room_id, %{"username" => username}, socket) do
5    send(self(), {:after_join, %{room_id: room_id, username: username}})
6    {:ok, assign(socket, room_id: room_id, username: username)}
7  end
8
9  def handle_info({:after_join, %{room_id: room_id, username: username}}, socket) do
10    broadcast!(socket, "new_peer", %{peer_id: socket.id, username: username})
11    {:noreply, socket}
12  end
13
14  def handle_in("peer_left", %{"peer_id" => peer_id}, socket) do
15    broadcast!(socket, "peer_left", %{peer_id: peer_id})
16    {:reply, :ok, socket}
17  end
18
19  # ... other handle_in functions
20
21end
This code broadcasts a new_peer event when a user joins and a peer_left event when they leave. The RoomLive module listens for these events and updates the participants list accordingly.
Finally, update the room_live.html.leex template to display the participants' video streams. Open lib/membrane_webrtc_app_web/templates/live/room_live.html.leex:

HTML

1<div>
2  <h1>Room: <%= @room_id %></h1>
3  <div id="video-streams">
4    <%= for participant <- @participants do %>
5      <div class="participant">
6        <video id="video-<%= participant.id %>" autoplay></video>
7        <p><%= participant.username %></p>
8      </div>
9    <% end %>
10  </div>
11  <div id="controls">
12    <button phx-click="mute"><%= if @muted, do: "Unmute", else: "Mute" %></button>
13    <button phx-click="toggle_video"><%= if @video_off, do: "Video On", else: "Video Off" %></button>
14    <button phx-click="hang_up">Hang Up</button>
15  </div>
16</div>
This template includes a for loop to iterate over the @participants list and display a video element for each participant.

Managing Participant States

Managing the states of participants, such as handling active speakers or indicating who is muted, enhances the interaction quality in a WebRTC session. You can extend the RoomLive module to update and display these states.
Add state management in the handle_event functions for mute and toggle video:

Elixir

1def handle_event("mute", _params, socket) do
2  muted = !socket.assigns.muted
3  broadcast(socket, "mute", %{peer_id: socket.id, muted: muted})
4  {:noreply, assign(socket, muted: muted)}
5end
6
7def handle_event("toggle_video", _params, socket) do
8  video_off = !socket.assigns.video_off
9  broadcast(socket, "toggle_video", %{peer_id: socket.id, video_off: video_off})
10  {:noreply, assign(socket, video_off: video_off)}
11end
Update the RoomChannel to handle these broadcasts:

Elixir

1def handle_in("mute", %{"peer_id" => peer_id, "muted" => muted}, socket) do
2  broadcast!(socket, "mute", %{peer_id: peer_id, muted: muted})
3  {:reply, :ok, socket}
4end
5
6def handle_in("toggle_video", %{"peer_id" => peer_id, "video_off" => video_off}, socket) do
7  broadcast!(socket, "toggle_video", %{peer_id: peer_id, video_off: video_off})
8  {:reply, :ok, socket}
9end
And update the RoomLive module to manage these events:

Elixir

1def handle_info(%{event: "mute", payload: %{peer_id: peer_id, muted: muted}}, socket) do
2  participants = Enum.map(socket.assigns.participants, fn
3    p when p.id == peer_id -> %{p | muted: muted}
4    p -> p
5  end)
6  {:noreply, assign(socket, participants: participants)}
7end
8
9def handle_info(%{event: "toggle_video", payload: %{peer_id: peer_id, video_off: video_off}}, socket) do
10  participants = Enum.map(socket.assigns.participants, fn
11    p when p.id == peer_id -> %{p | video_off: video_off}
12    p -> p
13  end)
14  {:noreply, assign(socket, participants: participants)}
15end
This ensures that the state of each participant is updated in real-time and displayed correctly.

Step 6: Run Your Code Now

Running the Application

Now that all the components of your Membrane WebRTC application are implemented, it's time to run your code and see everything in action. Follow these steps to start your application:

[a] Compile the Project

Ensure that all dependencies are compiled and up to date. Run the following command in your terminal:

bash

1   mix deps.get
2   mix compile

[b] Start the Phoenix Server

Start the Phoenix development server to run your application locally:

bash

1   mix phx.server
Your application will be available at http://localhost:4000.

[c] Access the Application

Open a web browser and navigate to http://localhost:4000. You should see the join screen where you can enter a username and room ID.

[d] Join a Room

Enter a username and a room ID to join the room. Open the same URL in multiple browser tabs or different browsers to simulate multiple participants joining the room.

[e] Test the Controls

  • Mute/Unmute: Test the mute button to ensure it mutes and unmutes the audio correctly.
  • Video On/Off: Test the video toggle button to turn the video on and off.
  • Hang Up: Test the hang-up button to leave the room and close the connection.

[f] Check the Participant View

Ensure that all participants' video streams are displayed correctly in each browser tab. Verify that the state updates (mute, video off) are reflected in real-time across all participants.

Testing and Debugging

Testing and debugging are crucial to ensure your application runs smoothly. Here are some tips to help you with this process:

[a] Console Logs

Use IO.inspect/2 in Elixir and console.log in JavaScript to print useful information to the console. This can help you understand the flow of data and identify any issues.

[b] Phoenix Live Dashboard

Phoenix Live Dashboard provides real-time performance monitoring and debugging tools for your Phoenix application. Add it to your project by updating your mix.exs:

Elixir

1   defp deps do
2     [
3       {:phoenix_live_dashboard, "~> 0.6"}
4     ]
5   end
Fetch the new dependency:

bash

1   mix deps.get
Add the dashboard route to your router:

Elixir

1   scope "/" do
2     pipe_through :browser
3     live_dashboard "/dashboard", metrics: MembraneWebrtcAppWeb.Telemetry
4   end
Access the dashboard at http://localhost:4000/dashboard for real-time insights.

[c] WebRTC Internals

Modern browsers provide a chrome://webrtc-internals (in Chrome) page where you can inspect WebRTC connections. This tool is invaluable for debugging WebRTC-specific issues.

[d] Unit Tests

Write unit tests for your Elixir code using ExUnit. Create test files in the test directory and run your tests with:

bash

1   mix test

[e] Network and Performance Testing:

Simulate different network conditions to ensure your application performs well under various scenarios. Tools like

Network Link Conditioner

 (for macOS) can help.

[f] Error Handling

Ensure that your application gracefully handles errors. For instance, if a user loses connection, display a helpful message and try to reconnect.
By following these steps and tips, you can run, test, and debug your Membrane WebRTC application effectively, ensuring a robust and user-friendly experience.

Conclusion

In this article, we have explored how to build a WebRTC application using the Membrane framework. We started with an introduction to Membrane WebRTC, highlighting its key features and advantages. We then walked through setting up the environment, creating a new Membrane WebRTC application, and configuring the necessary components. Following this, we designed and implemented the join screen, added essential control features, and managed participant views. Finally, we ran the application, tested it, and provided tips for debugging.
Membrane WebRTC, with its modular architecture and robust performance, offers a powerful solution for real-time communication applications. By following the steps outlined in this guide, you can create a scalable and efficient WebRTC application tailored to your specific needs.

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