1.主要流程

• 录屏（涉及的Android Api: MediaProjectionManager, MediaProjection,VirtualDisplay可以参考：https://blog.csdn.net/ss182172633/article/details/79480853）
• 编码(通常编为：H264编码，使用api: MediaCodec)
• 封包(使用的API：MediaMuxer)
• 发送(rtsp)

2.关于开源项目：ScreenRecorder

• 在界面中获取所有可配置的信息EncodeConfig（MediaCodec，MediaMuxer都会使用）
• 主要方法：
  获取MediaProjectionManager实例

mMediaProjectionManager = (MediaProjectionManager) getApplicationContext().getSystemService(MEDIA_PROJECTION_SERVICE);

• 录屏授权

 Intent captureIntent = mMediaProjectionManager.createScreenCaptureIntent();
 startActivityForResult(captureIntent, REQUEST_MEDIA_PROJECTION);

• 授权后获取实例

MediaProjection mediaProjection = mMediaProjectionManager.getMediaProjection(resultCode, data);

VirtualDisplay virtualDisplay  = mediaProjection.createVirtualDisplay("ScreenRecorder-display0",
                    config.width, config.height, 1 /*dpi*/,
                    DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC,
                    null /*surface*/, null, null);

mVirtualDisplay.setSurface(mVideoEncoder.getInputSurface());

• 创建封包器并丢数据进出

mMuxer = new MediaMuxer(mDstPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
writeSampleData(mVideoTrackIndex, buffer, encodedData);

• 通过MediaCodec获取h264数据

MediaFormat format = createMediaFormat();
        Log.d("Encoder", "Create media format: " + format);

        String mimeType = format.getString(MediaFormat.KEY_MIME);
        final MediaCodec encoder = createEncoder(mimeType);
        try {
            if (this.mCallback != null) {
                // NOTE: MediaCodec maybe crash on some devices due to null callback
                encoder.setCallback(mCodecCallback);
            }
            encoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
            onEncoderConfigured(encoder);
            encoder.start();
        } catch (MediaCodec.CodecException e) {
            Log.e("Encoder", "Configure codec failure!\n  with format" + format, e);
            throw e;
        }

• MediaCodec 运行状态，编码后的数据通过回掉返回

 /**
     * let media codec run async mode if mCallback != null
     */
    private MediaCodec.Callback mCodecCallback = new MediaCodec.Callback() {
        @Override
        public void onInputBufferAvailable(MediaCodec codec, int index) {
            mCallback.onInputBufferAvailable(BaseEncoder.this, index);
        }

        @Override
        public void onOutputBufferAvailable(MediaCodec codec, int index, MediaCodec.BufferInfo info) {
            mCallback.onOutputBufferAvailable(BaseEncoder.this, index, info);
        }

        @Override
        public void onError(MediaCodec codec, MediaCodec.CodecException e) {
            mCallback.onError(BaseEncoder.this, e);
        }

        @Override
        public void onOutputFormatChanged(MediaCodec codec, MediaFormat format) {
            mCallback.onOutputFormatChanged(BaseEncoder.this, format);
        }
    };