mProjectionManager = (MediaProjectionManager)getSystemService(Context.MEDIA_PROJECTION_SERVICE);
startActivityForResult(mProjectionManager.createScreenCaptureIntent(), REQUEST_CODE);

mMediaCodec = MediaCodec.createEncoderByType(MIME_TYPE);
Surface surface = mMediaCodec.createInputSurface();
mMediaProjection = projectionManager.getMediaProjection(resultCode, resultData);
mVirtualDisplay = mMediaProjection.createVirtualDisplay("H264VDisplay",
                    width, height, dpi,
                    DisplayManager.VIRTUAL_DISPLAY_FLAG_PRESENTATION,
                    surface, null, null);

Camera.Parameters parameters = this.mCamera.getParameters();
parameters.setPreviewFormat(ImageFormat.NV21);  //摄像头配置
...
int colorFormat = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar;
mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, colorFormat); //编码器配置
...
// 转换操作
private void swapNV21toI420SemiPlanar(byte[] source, int width, int height) {
    for (int i = width * height; i < source.length; i += 2) {
        byte temp = source[i];
        source[i] = source[i + 1];
        source[i + 1] = temp;
    }
}

MediaCodec codec = MediaCodec.createByCodecName(name);
codec.start();
for (;;) {
    // 写入输入缓冲区
    int inputBufferId = codec.dequeueInputBuffer(timeoutUs);
    if (inputBufferId >= 0) {
        ByteBuffer inputBuffer = codec.getInputBuffer(…);
        // fill inputBuffer with valid data
        …
        codec.queueInputBuffer(inputBufferId, …);
    }
    // 读取输出缓冲区
    int outputBufferId = codec.dequeueOutputBuffer(…);
    if (outputBufferId >= 0) {
        ByteBuffer outputBuffer = codec.getOutputBuffer(outputBufferId);
        MediaFormat bufferFormat = codec.getOutputFormat(outputBufferId); // option A
        // bufferFormat is identical to outputFormat
        // outputBuffer is ready to be processed or rendered.
        …
        codec.releaseOutputBuffer(outputBufferId, …);
    }
}

MediaCodec codec = MediaCodec.createByCodecName(name);
codec.setCallback(new MediaCodec.Callback() {
    @Override
    void onInputBufferAvailable(MediaCodec mc, int inputBufferId) {
    ByteBuffer inputBuffer = codec.getInputBuffer(inputBufferId);
    // fill inputBuffer with valid data
    …
    codec.queueInputBuffer(inputBufferId, …);
    }

    @Override
    void onOutputBufferAvailable(MediaCodec mc, int outputBufferId, …) {
    ByteBuffer outputBuffer = codec.getOutputBuffer(outputBufferId);
    MediaFormat bufferFormat = codec.getOutputFormat(outputBufferId); // option A
    // bufferFormat is equivalent to mOutputFormat
    // outputBuffer is ready to be processed or rendered.
    …
    codec.releaseOutputBuffer(outputBufferId, …);
    }
});