Video filters
A very common use case during a video call is to apply some effect on our backgrounds. Those backgrounds can vary but the most common ones are blurring and adding a static image. Our SDK offers background blurring and virtual backgrounds with static images out of the box and also has support for injecting your custom filter into the calling experience. In this guide, we will show you how to apply video filters to a video stream.
Using the background video filters provided by the SDK
Step 1 - Install the video filters library
To enable background filters in your app. You must first add the @stream-io/video-filters-react-native library.
yarn add @stream-io/video-filters-react-native
This library adds the required native module for processing the video stream and manipulating it with your desired video filter.
For iOS, the library is written in Swift. In order for Xcode to build the app when you use the library, your main app project must contain Swift code and a bridging header file. If your app project does not contain any Swift code yet, a simple workaround is to add a single empty .swift file and an empty bridging header.
Step 2 - Wrap under Provider component
Background filters are provided through the following APIs and components:
<BackgroundFiltersProvider />- a React context provider that will allow you to use the filters API in your application.useBackgroundFilters()- a React hook that will allow you to access the filters API in your application
A basic integration looks like this:
import {
BackgroundFiltersProvider,
Call,
StreamCall,
StreamVideo,
StreamVideoClient,
} from '@stream-io/video-react-native-sdk';
export default function App() {
let client: StreamVideoClient; /* = ... */
let call: Call; /* = ... */
return (
<StreamVideo client={client}>
<StreamCall call={call}>
<BackgroundFiltersProvider>
<MyCallContent />
<MyBackgroundFilterUI /> {/* your UI to enable or disable filters, for example a modal dialog */}
</BackgroundFiltersProvider>
</StreamCall>
</StreamVideo>
);
}
The BackgroundFiltersProvider holds the state of the background filters in the app. It must be wrapped under the StreamCall component so that the media stream of the call can be accessed.
Step 2 - Use the hook to control the filters
Once you have the BackgroundFiltersProvider rendered in your application,
you can use the useBackgroundFilters() hook to access the filters API and control the behavior of the filters.
In iOS, the background video filters are supported only on iOS 15 and above. However, the iOS platform's minimum level of support for the custom filters that you may add depends on what APIs you would use.
import { useBackgroundFilters } from '@stream-io/video-react-native-sdk';
export const MyBackgroundFilterUI = () => {
const {
isSupported, // checks if these filters can run on this device
disableAllFilter // disables all the video filters
applyBackgroundBlurFilter, // applies the blur filter
applyBackgroundImageFilter, // applies the image filter
currentBackgroundFilter, // the currently applied filter
} = useBackgroundFilters();
if (!isSupported) {
return null;
}
return (
<SafeAreaView>
<Button onPress={disableBackgroundFilter} title="Disable"/>
<Button onPress={() => applyBackgroundBlurFilter('heavy')} title="Blur Heavy"/>
<Button onPress={() => applyBackgroundBlurFilter('medium')} title="Blur Medium">
<Button onPress={() => applyBackgroundBlurFilter('light')} title="Blur Light"/>
<Button onPress={() => applyBackgroundImageFilter(require('path/to/image/amsterdam.png'))} title="Amsterdam Local Image Background"/>
<Button onPress={() => applyBackgroundImageFilter({uri: 'https://upload.wikimedia.org/wikipedia/commons/1/18/React_Native_Logo.png'})} title="React Native Remote Image Background"/>
</SafeAreaView>
);
};
| Preview of background blur filter | Preview of background image replacement filter |
|---|---|
 |  |
Advanced: adding custom video filters
Step 1 - Add your custom filter natively in Android and iOS
For Expo, make sure to create a new Expo local module first if you do not have any existing module set up already.
- Android
- iOS
To create a new video filter, you need to implement the VideoFrameProcessorFactoryInterface from @stream-io/react-native-webrtc. A simple example that applies rotation to the video filter would be like the following:
import com.oney.WebRTCModule.videoEffects.VideoFrameProcessor
import com.oney.WebRTCModule.videoEffects.VideoFrameProcessorFactoryInterface
import org.webrtc.VideoFrame
class RotationFilterFactory : VideoFrameProcessorFactoryInterface {
override fun build(): VideoFrameProcessor {
return VideoFrameProcessor { frame, textureHelper ->
VideoFrame(
frame.buffer.toI420(),
180, // apply rotation to the video frame
frame.timestampNs
)
}
}
}
For the easiness of processing video frames in Bitmap, we export a VideoFrameProcessorWithBitmapFilter class from the @stream-io/video-filters-react-native library. The built-in background filters of the library have been implemented using this class. To implement a video filter with Bitmap, create a class by extending a filter that extends from BitmapVideoFilter abstract class. This BitmapVideoFilter abstract class gives you a Bitmap for each video frame, which you can manipulate directly. By returning a new VideoFrameProcessorWithBitmapFilter instance with that filter we can implement a bitmap processing filter.
BitmapVideoFilter is less performant than a normal video filter that does not use bitmaps. It is due to the overhead of certain operations, like YUV <-> ARGB conversions.
Example: grayscale video filter
We can create and set a simple video filter that turns the video frame to grayscale by extending a filter that extends from BitmapVideoFilter abstract class like this:
import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.ColorMatrix
import android.graphics.ColorMatrixColorFilter
import android.graphics.Paint
import com.oney.WebRTCModule.videoEffects.VideoFrameProcessor
import com.oney.WebRTCModule.videoEffects.VideoFrameProcessorFactoryInterface
import com.streamio.videofiltersreactnative.common.BitmapVideoFilter
import com.streamio.videofiltersreactnative.common.VideoFrameProcessorWithBitmapFilter
class GrayScaleVideoFilterFactory : VideoFrameProcessorFactoryInterface {
override fun build(): VideoFrameProcessor {
return VideoFrameProcessorWithBitmapFilter {
GrayScaleFilter()
}
}
}
private class GrayScaleFilter : BitmapVideoFilter() {
override fun applyFilter(videoFrameBitmap: Bitmap) {
val canvas = Canvas(videoFrameBitmap)
val paint = Paint().apply {
val colorMatrix = ColorMatrix().apply {
// map the saturation of the color to grayscale
setSaturation(0f)
}
colorFilter = ColorMatrixColorFilter(colorMatrix)
}
canvas.drawBitmap(videoFrameBitmap, 0f, 0f, paint)
}
}
To add a new video filter, you need to specify an object that conforms to the VideoFrameProcessorDelegate protocol from the @stream-io/video-filters-react-native library and inherits from the NSObject class.
For the easiness of processing video frames in CIImage, copy this VideoFilters.swift file into your app. How does this class work? If you implement the filter using the VideoFilter class, you will receive each frame of the user's local video as CIImage, allowing you to apply the filters. The VideoFilter class allows you to easily create your own filters. It contains the function that converts the original CIImage to an output CIImage. This way you have complete freedom over the processing pipeline. Instead, if you would need to access the raw video frame you can look into the implementation of VideoFilter class and adapt it to your own filter.
Additionally, you will need to import the necessary headers in the bridging header file. This header file is to expose the Objective-C files to Swift. If it is the first Swift file that you add to your app, Xcode will automatically offer to create a bridging header file. Your bridging header file should minimally have the two following header imports:
#import <React/RCTBridgeModule.h>
#import "ProcessorProvider.h"
Example: grayscale video filter
We can create and set a simple video filter that turns the video frame to grayscale by extending a filter class that extends from VideoFilter class like this:
import Foundation
final class GrayScaleVideoFrameProcessor: VideoFilter {
@available(*, unavailable)
override public init(
filter: @escaping (Input) -> CIImage
) { fatalError() }
init() {
super.init(
filter: { input in
let filter = CIFilter(name: "CIPhotoEffectMono")
filter?.setValue(input.originalImage, forKey: kCIInputImageKey)
let outputImage: CIImage = filter?.outputImage ?? input.originalImage
return outputImage
}
)
}
}
Step 2 - Register this filter in your native module
Now you have to add a method in your app to register this video filter to the @stream-io/video-filters-react-native library.
- Android
- iOS
Follow the official React Native documentation to create a new Android native module if there is no native module in your app already. In that native module, add a method to add the filter to the ProcessorProvider from the @stream-io/video-filters-react-native library. For example:
import com.facebook.react.bridge.Promise
import com.facebook.react.bridge.ReactApplicationContext
import com.facebook.react.bridge.ReactContextBaseJavaModule
import com.facebook.react.bridge.ReactMethod
import com.oney.WebRTCModule.videoEffects.ProcessorProvider
import io.getstream.rnvideosample.videofilters.GrayScaleVideoFilterFactory
class VideoEffectsModule (reactContext: ReactApplicationContext) : ReactContextBaseJavaModule(reactContext) {
override fun getName(): String {
return NAME;
}
@ReactMethod
fun registerVideoFilters(promise: Promise) {
ProcessorProvider.addProcessor("grayscale", GrayScaleVideoFilterFactory())
promise.resolve(true)
}
companion object {
private const val NAME = "VideoEffectsModule"
}
}
In this step, we add a method to our iOS native module in Swift. If there is no native module in your app already, add a new one. In that native module, add a method to add the filter to the ProcessorProvider from the @stream-io/video-filters-react-native library. For example:
@objc(VideoEffectsModule)
class VideoEffectsModule: NSObject {
@objc(registerVideoFilters:withRejecter:)
func registerVideoFilters(resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) {
ProcessorProvider.addProcessor(GrayScaleVideoFrameProcessor(), forName: "grayscale")
resolve(true)
}
}
It is important to use the @objc modifiers to ensure the class and functions are exported properly to the Objective-C runtime.
Then create a private implementation file that will register the required information with React Native:
#import <React/RCTBridgeModule.h>
@interface RCT_EXTERN_MODULE(VideoEffectsModule, NSObject)
RCT_EXTERN_METHOD(registerVideoFilters:(RCTPromiseResolveBlock)resolve
withRejecter:(RCTPromiseRejectBlock)reject)
+ (BOOL)requiresMainQueueSetup
{
return NO;
}
@end
While calling the addProcessor method. We need to provide a name to the filter that we are registering. In the above example, it is grayscale. This name is to be later called in JavaScript.
Step 3 - Apply the video filter in JavaScript
To apply this video filter. You have to call the method mediaStreamTrack._setVideoEffect(name). To disable the filters you have to call the method mediaStreamTrack._setVideoEffect(null) or you can call the disableAllFilter method from the useBackgroundFilters() hook. Below is a small example of a hook that can be used to apply the grayscale video filter that we created. Note that the media stream is present inside the Call instance returned from the useCall hook.
import {
useBackgroundFilters,
useCall,
} from '@stream-io/video-react-native-sdk';
import { useRef, useCallback, useState } from 'react';
import { MediaStream } from '@stream-io/react-native-webrtc';
import { NativeModules, Platform } from 'react-native';
type CustomFilters = 'GrayScale' | 'MyOtherCustomFilter';
export const useCustomVideoFilters = () => {
const call = useCall();
const isFiltersRegisteredRef = useRef(false);
const { disableAllFilters } = useBackgroundFilters();
const [currentCustomFilter, setCustomFilter] = useState<CustomFilters>();
const applyGrayScaleFilter = useCallback(async () => {
if (!isFiltersRegisteredRef.current) {
// registering is needed only once per the app's lifetime
await NativeModules.VideoEffectsModule?.registerVideoFilters();
isFiltersRegisteredRef.current = true;
}
disableAllFilters(); // disable any other filter
(call?.camera.state.mediaStream as MediaStream | undefined)
?.getVideoTracks()
.forEach((track) => {
track._setVideoEffect('grayscale'); // set the grayscale filter
});
setCustomFilter('GrayScale');
}, [call, disableAllFilters]);
const disableCustomFilter = useCallback(() => {
disableAllFilters();
setCustomFilter(undefined);
}, [disableAllFilters]);
return {
currentCustomFilter,
applyGrayScaleFilter,
disableCustomFilter,
};
};
Below is a preview of the above grayscale video filter:
When using a custom filter along with the built-in background filters, always call the disableAllFilter method from the useBackgroundFilters() hook so that the state inside the hook is informed if the built-in filters have been disabled.