How to achieve real time video editing on Android?

In Android, implementing real-time video editing can be achieved through the following steps:

1. Video Capture

First, use the Camera2 API to capture video streams. The Camera2 API is a more modern camera interface provided by Android, offering greater control and higher efficiency compared to the older Camera API.

java
CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
String cameraId = manager.getCameraIdList()[0]; // Get camera ID
CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
Size[] sizes = map.getOutputSizes(SurfaceTexture.class);

2. Video Processing

For real-time processing of video streams, use OpenGL ES for image rendering and applying filter effects. OpenGL ES efficiently leverages the GPU for image processing, making it ideal for applications demanding real-time performance.

java
EGLContext ctxt = EGL14.eglGetCurrentContext();
GLSurfaceView glView = new GLSurfaceView(this);
glView.setEGLContextClientVersion(2);
glView.setRenderer(new VideoRenderer());

3. Using External Libraries

Powerful video processing libraries like FFmpeg can be used for decoding and encoding video streams. FFmpeg supports various video formats and codecs, enabling efficient conversion and processing of video data.

java
FFmpeg ffmpeg = FFmpeg.getInstance(context);
ffmpeg.loadBinary(new LoadBinaryResponseHandler() {
    @Override
    public void onStart() {}
    @Override
    public void onFailure() {}
    @Override
    public void onSuccess() {}
    @Override
    public void onFinish() {}
});

4. Real-time Filters and Effects

By combining OpenGL ES with Shader programming, various real-time filters and effects can be created. For example, effects such as blurring, color transformations, and edge detection can be implemented.

glsl
precision mediump float;
uniform sampler2D u_Texture;
varying vec2 v_TexCoordinate;
void main() {
    float blurSize = 1.0 / 512.0;
    vec4 sum = vec4(0.0);
    for (int x = -4; x <= 4; x++) {
        for (int y = -4; y <= 4; y++) {
            vec2 step = vec2(blurSize * float(x), blurSize * float(y));
            sum += texture2D(u_Texture, v_TexCoordinate + step);
        }
    }
    gl_FragColor = sum / 81.0;
}

5. Audio-Video Synchronization

In video editing, beyond image processing, it is crucial to address audio-video synchronization. This can typically be achieved by calibrating the timestamps of audio and video streams.

6. Performance Optimization

Real-time video processing demands high performance and appropriate optimizations, such as utilizing multithreading, minimizing memory copies, and refining algorithms.

Example Application Scenario

Suppose we are developing a live streaming application where users can add real-time beauty filters during the stream. Using the Camera2 API to capture video streams, processing image data with OpenGL ES, and applying custom shaders for beauty effects, finally encoding and pushing the processed video stream to the server using FFmpeg.

By following these steps, you can achieve efficient real-time video editing on Android devices.