With HTML5 came the introduction of APIs with access to device hardware, including the MediaDevices API. This API provides access to media input devices like audio and video.
With this API’s help, developers can access audio and video devices to stream and display live video feeds in the browser. In this tutorial, you’ll access the video feed from the user’s device and display it in the browser using the getUserMedia
method.
The getUserMedia
API makes use of the media input devices to produce a MediaStream. This MediaStream contains the requested media types, whether audio or video. Using the stream returned from the API, video feeds can be displayed on the browser, which is useful for real-time communication on the browser.
When used along with the MediaStream Recording API, you can record and store media data captured on the browser. This API only works on secure origins like the rest of the newly introduced APIs, but it also works on localhost
and file URLs.
This tutorial will first explain concepts and demonstrate examples with Codepen. In the final step, you will create a functioning video feed for the browser.
First, you will see how to check if the user’s browser supports the mediaDevices
API. This API exists within the navigator interface and contains the current state and identity of the user agent. The check is performed with the following code that can be pasted into Codepen:
if ('mediaDevices' in navigator && 'getUserMedia' in navigator.mediaDevices) {
console.log("Let's get this party started")
}
First, this checks if the mediaDevices
API exists within the navigator
and then checks if the getUserMedia
API is available within the mediaDevices
. If this returns true
, you can get started.
After confirming the browser’s support for getUserMedia
, you need to request permission to make use of the media input devices on the user agent. Typically, after a user grants permission, a Promise
is returned which resolves to a media stream. This Promise
isn’t returned when the permission is denied by the user, which blocks access to these devices.
Paste the following line into Codepen to request permission:
navigator.mediaDevices.getUserMedia({video: true})
The object provided as an argument for the getUserMedia
method is called constraints
. This determines which of the media input devices you are requesting permissions to access. For example, if the object contains audio: true
, the user will be asked to grant access to the audio input device.
This section will cover the general concept of contraints
. The constraints
object is a MediaStreamConstraints
object that specifies the types of media to request and the requirements of each media type. You can specify requirements for the requested stream using the constraints
object, like the resolution of the stream to use (front
, back
).
You must specify either audio
or video
when making the request. A NotFoundError
will be returned if the requested media types can’t be found on the user’s browser.
If you intend to request a video stream of 1280 x 720
resolution, you can update the constraints
object to look like this:
{
video: {
width: 1280,
height: 720,
}
}
With this update, the browser will try to match the specified quality settings for the stream. If the video device can’t deliver this resolution, the browser will return other available resolutions.
To ensure that the browser returns a resolution not lower than the one provided you will have to make use of the min
property. Here is how you could update the constraints
object to include the min
property:
{
video: {
width: {
min: 1280,
},
height: {
min: 720,
}
}
}
This will ensure that the stream resolution returned will be at least 1280 x 720
. If this minimum requirement can’t be met, the promise will be rejected with an OverconstrainedError
.
In some cases you may be concerned about saving data and need the stream to not exceed a set resolution. This can come in handy when the user is on a limited plan. To enable this functionality, update the constraints object to contain a max
field:
{
video: {
width: {
min: 1280,
max: 1920,
},
height: {
min: 720,
max: 1080
}
}
}
With these settings, the browser will ensure that the return stream doesn’t go below 1280 x 720
and doesn’t exceed 1920 x 1080
.
Other terms that can be used includes exact
and ideal
. The ideal
setting is typically used along with the min
and max
properties to find the best possible setting closest to the ideal values provided.
You can update the constraints to use the ideal
keyword:
{
video: {
width: {
min: 1280,
ideal: 1920,
max: 2560,
},
height: {
min: 720,
ideal: 1080,
max: 1440
}
}
}
To tell the browser to make use of the front or back (on mobile) camera on devices, you can specify a facingMode
property in the video
object:
{
video: {
width: {
min: 1280,
ideal: 1920,
max: 2560,
},
height: {
min: 720,
ideal: 1080,
max: 1440
},
facingMode: 'user'
}
}
This setting will make use of the front-facing camera at all times in all devices. To make use of the back camera on mobile devices, you can alter the facingMode
property to environment
.
{
video: {
...
facingMode: {
exact: 'environment'
}
}
}
enumerateDevices
MethodWhen the enumerateDevices
method is called, it returns all of the available input media devices available on the user’s PC.
With the method, you can provide the user options on which input media device to use for streaming audio or video content. This method returns a Promise
resolved to a MediaDeviceInfo array containing information about each device.
An example of how to make a use of this method is shown in the snippet below:
async function getDevices() {
const devices = await navigator.mediaDevices.enumerateDevices();
}
A sample response for each of the devices would look like the following:
{
deviceId: "23e77f76e308d9b56cad920fe36883f30239491b8952ae36603c650fd5d8fbgj",
groupId: "e0be8445bd846722962662d91c9eb04ia624aa42c2ca7c8e876187d1db3a3875",
kind: "audiooutput",
label: "",
}
Note: A label won’t be returned unless an available stream is available, or if the user has granted device access permissions.
You have gone through the process of requesting and getting access to the media devices, configured constraints to include required resolutions, and selected the camera you will need to record video.
After going through all these steps, you’ll at least want to see if the stream is delivering based on the configured settings. To ensure this, you will make use of the <video>
element to display the video stream on the browser.
Like mentioned earlier, the getUserMedia
method returns a Promise
that can be resolved to a stream. The returned stream can be converted to an object URL using the createObjectURL
method. This URL will be set as a video source.
You will create a short demo where we let the user choose from their available list of video devices. using the enumerateDevices
method.
This is a navigator.mediaDevices
method. It lists the available media devices, such as microphones and cameras. It returns a Promise
resolvable to an array of objects detailing the available media devices.
Create an index.html
file and update the contents with the code below:
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<link rel="stylesheet" href="style.css">
<title>Document</title>
</head>
<body>
<div class="display-cover">
<video autoplay></video>
<canvas class="d-none"></canvas>
<div class="video-options">
<select name="" id="" class="custom-select">
<option value="">Select camera</option>
</select>
</div>
<img class="screenshot-image d-none" alt="">
<div class="controls">
<button class="btn btn-danger play" title="Play"><i data-feather="play-circle"></i></button>
<button class="btn btn-info pause d-none" title="Pause"><i data-feather="pause"></i></button>
<button class="btn btn-outline-success screenshot d-none" title="ScreenShot"><i data-feather="image"></i></button>
</div>
</div>
<script src="https://unpkg.com/feather-icons"></script>
<script src="script.js"></script>
</body>
</html>
In the snippet above, you have set up the elements you will need and a couple of controls for the video. Also included is a button for taking screenshots of the current video feed.
Now, let’s style up these components a bit.
Create a style.css
file and copy the following styles into it. Bootstrap was included to reduce the amount of CSS you will need to write to get the components going.
.screenshot-image {
width: 150px;
height: 90px;
border-radius: 4px;
border: 2px solid whitesmoke;
box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.1);
position: absolute;
bottom: 5px;
left: 10px;
background: white;
}
.display-cover {
display: flex;
justify-content: center;
align-items: center;
width: 70%;
margin: 5% auto;
position: relative;
}
video {
width: 100%;
background: rgba(0, 0, 0, 0.2);
}
.video-options {
position: absolute;
left: 20px;
top: 30px;
}
.controls {
position: absolute;
right: 20px;
top: 20px;
display: flex;
}
.controls > button {
width: 45px;
height: 45px;
text-align: center;
border-radius: 100%;
margin: 0 6px;
background: transparent;
}
.controls > button:hover svg {
color: white !important;
}
@media (min-width: 300px) and (max-width: 400px) {
.controls {
flex-direction: column;
}
.controls button {
margin: 5px 0 !important;
}
}
.controls > button > svg {
height: 20px;
width: 18px;
text-align: center;
margin: 0 auto;
padding: 0;
}
.controls button:nth-child(1) {
border: 2px solid #D2002E;
}
.controls button:nth-child(1) svg {
color: #D2002E;
}
.controls button:nth-child(2) {
border: 2px solid #008496;
}
.controls button:nth-child(2) svg {
color: #008496;
}
.controls button:nth-child(3) {
border: 2px solid #00B541;
}
.controls button:nth-child(3) svg {
color: #00B541;
}
.controls > button {
width: 45px;
height: 45px;
text-align: center;
border-radius: 100%;
margin: 0 6px;
background: transparent;
}
.controls > button:hover svg {
color: white;
}
The next step is to add functionality to the demo. Using the enumerateDevices
method, you will get the available video devices and set it as the options within the select element. Create a file called script.js
and update it with the following snippet:
feather.replace();
const controls = document.querySelector('.controls');
const cameraOptions = document.querySelector('.video-options>select');
const video = document.querySelector('video');
const canvas = document.querySelector('canvas');
const screenshotImage = document.querySelector('img');
const buttons = [...controls.querySelectorAll('button')];
let streamStarted = false;
const [play, pause, screenshot] = buttons;
const constraints = {
video: {
width: {
min: 1280,
ideal: 1920,
max: 2560,
},
height: {
min: 720,
ideal: 1080,
max: 1440
},
}
};
const getCameraSelection = async () => {
const devices = await navigator.mediaDevices.enumerateDevices();
const videoDevices = devices.filter(device => device.kind === 'videoinput');
const options = videoDevices.map(videoDevice => {
return `<option value="${videoDevice.deviceId}">${videoDevice.label}</option>`;
});
cameraOptions.innerHTML = options.join('');
};
play.onclick = () => {
if (streamStarted) {
video.play();
play.classList.add('d-none');
pause.classList.remove('d-none');
return;
}
if ('mediaDevices' in navigator && navigator.mediaDevices.getUserMedia) {
const updatedConstraints = {
...constraints,
deviceId: {
exact: cameraOptions.value
}
};
startStream(updatedConstraints);
}
};
const startStream = async (constraints) => {
const stream = await navigator.mediaDevices.getUserMedia(constraints);
handleStream(stream);
};
const handleStream = (stream) => {
video.srcObject = stream;
play.classList.add('d-none');
pause.classList.remove('d-none');
screenshot.classList.remove('d-none');
streamStarted = true;
};
getCameraSelection();
In the snippet above, there are a couple of things going on. Let’s break them down:
feather.replace()
: this method call instantiates feather, which is an icon set for web development.constraints
variable holds the initial configuration for the stream. This will be extended to include the media device the user chooses.getCameraSelection
: this function calls the enumerateDevices
method. Then, you filter through the array from the resolved Promise
and select video input devices. From the filtered results, you create <option>
for the <select>
element.getUserMedia
method happens within the onclick
listener of the play
button. Here, you will check if this method is supported by the user’s browser before starting the stream.startStream
function that takes a constraints
argument. It calls the getUserMedia
method with the provided constraints
. handleStream
is called using the stream from the resolved Promise
. This method sets the returned stream to the video element’s srcObject
.Next, you will add click listeners to the button controls on the page to pause
, stop
, and take screenshots
. Also, you will add a listener to the <select>
element to update the stream constraints with the selected video device.
Update the script.js
file with the code below:
...
cameraOptions.onchange = () => {
const updatedConstraints = {
...constraints,
deviceId: {
exact: cameraOptions.value
}
};
startStream(updatedConstraints);
};
const pauseStream = () => {
video.pause();
play.classList.remove('d-none');
pause.classList.add('d-none');
};
const doScreenshot = () => {
canvas.width = video.videoWidth;
canvas.height = video.videoHeight;
canvas.getContext('2d').drawImage(video, 0, 0);
screenshotImage.src = canvas.toDataURL('image/webp');
screenshotImage.classList.remove('d-none');
};
pause.onclick = pauseStream;
screenshot.onclick = doScreenshot;
Now, when you open the index.html
file in the browser, clicking the Play button will start the stream.
Here is a complete demo:
https://codepen.io/chrisbeast/pen/ebYwpX
This tutorial introduced the getUserMedia
API. It is an interesting addition to HTML5 that eases the process of capturing media on the web.
The API takes a parameter (constraints
) that can be used to configure the access to audio and video input devices. It can also be used to specify the video resolution required for your application.
You can extend the demo further to give the user an option to save the screenshots taken, as well as recording and storing video and audio data with the help of MediaStream Recording API.
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This code as-is gives a black screen. It seems the issue is that the “deviceId” parameter is set outside of the “video” section in “updatedConstraints”. Putting “deviceId” in the video section fixes the camera selection and the black screen issue. “updatedConstraints” assignment needs to be re-written to include “deviceId” inside the “video” section. It would be best to just convert “constraints” to a variable and dynamically assign the “deviceId” as needed instead of trying to compose another constant.
This doesn not work on ios 14. The camera’s are recognized, but I get a black screen. Do you know why?
Hello, I can call the camera when I test locally, but I can’t find the media device when I upload it to the server. Do you know why?