README-EN.md

Screen Recorder

This is a DEMO APP that mainly implements the screen recording function (it can also record the sound from the microphone).

Click here to download APK Quick preview of project functions

Note: It uses APIs such as MediaProjectionManager, VirtualDisplay, AudioRecord, MediaCodec and MediaMuxer, so this project supports at least Android 5.0.

Screen Recording Principles

** Note ** You can checkout 32c005412 to view the original code (excluding microphone recording)

• Display can be "projected" to a VirtualDisplay
• Create a VirtualDisplay through a MediaProjection obtained from MediaProjectionManager
• VirtualDisplay will render the image to a Surface, which is created by MediaCodec

mEncoder = MediaCodec.createEncoderByType(MIME_TYPE);
...
mSurface = mEncoder.createInputSurface();
...
mVirtualDisplay = mMediaProjection.createVirtualDisplay(name, mWidth, mHeight, mDpi, DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC, mSurface, null, null);

• MediaMuxer encapsulates the image metadata obtained from MediaCodec and outputs it to the MP4 file

int index = mEncoder.dequeueOutputBuffer(mBufferInfo, TIMEOUT_US);
...
ByteBuffer encodedData = mEncoder.getOutputBuffer(index);
...
mMuxer.writeSampleData(mVideoTrackIndex, encodedData, mBufferInfo);

So in fact, on Android 4.4, you can create VirtualDisplay through DisplayManager and also record the screen, but because of permission restrictions, ROOT is required. (see DisplayManager.createVirtualDisplay())