音視頻的採集、編碼、封包成 mp4 輸出

使用 Android Camera API 完成音視頻的採集、編碼、封包成 mp4 輸出基於android.hardware.Camera，創建一個橫屏應用，實時預覽攝像頭圖像，實現錄像並輸出MP4的功能。

1、申請權限

<code>
<uses-permission>
<uses-permission>
<uses-permission>
<uses-feature>
/<code>

在activity中動態申請權限

<code>private static final String[] VIDEO_PERMISSIONS = {
        Manifest.permission.CAMERA,
        Manifest.permission.RECORD_AUDIO,
        Manifest.permission.WRITE_EXTERNAL_STORAGE
};
/<code>

2、實現攝像頭預覽功能

使用SurfaceView來預覽。新建CameraPreview類繼承自SurfaceView並實現SurfaceHolder.Callback；Camera相關操作都放在這個View裡。surfaceCreated中獲取Camera實例，啟動預覽；設置預覽相關參數，surfaceDestroyed釋放Camera

<code>public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public static final int MEDIA_TYPE_IMAGE = 1;
    public static final int MEDIA_TYPE_VIDEO = 2;
    private static int mOptVideoWidth = 1920;  // 默認視頻幀寬度
    private static int mOptVideoHeight = 1080;
    private Uri outputMediaFileUri;
    private String outputMediaFileType;


    public CameraPreview(Context context) { 

        super(context);
        mHolder = getHolder();
        mHolder.addCallback(this);
    }

    private static Camera getCameraInstance() {
        Camera c = null;
        try {
            c = Camera.open();
        } catch (Exception e) {
            Log.d(TAG, "camera is not available");
        }
        return c;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mCamera = getCameraInstance();
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
            getCameraOptimalVideoSize(); // 找到最合適的分辨率
        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    private void getCameraOptimalVideoSize() {
        try {
            Camera.Parameters parameters = mCamera.getParameters();
            List<camera.size> mSupportedPreviewSizes = parameters.getSupportedPreviewSizes();
            List<camera.size> mSupportedVideoSizes = parameters.getSupportedVideoSizes();
            Camera.Size optimalSize = CameraHelper.getOptimalVideoSize(mSupportedVideoSizes,
                    mSupportedPreviewSizes, getWidth(), getHeight());
            mOptVideoWidth = optimalSize.width;
            mOptVideoHeight = optimalSize.height;
            Log.d(TAG, "prepareVideoRecorder: optimalSize:" + mOptVideoWidth + ", " + mOptVideoHeight);
        } catch (Exception e) {
            Log.e(TAG, "getCameraOptimalVideoSize: ", e);
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mHolder.removeCallback(this);
        mCamera.setPreviewCallback(null);
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    } 


    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
    }
}
/<camera.size>/<camera.size>/<code>

3、在Fragment中顯示攝像頭預覽

預置一個FrameLayout，實例化一個CameraPreview添加進去

<code>/**
 * 視頻錄製界面
 * Created by Rust on 2018/5/17.
 */
public class VideoRecordFragment extends Fragment {
    private static final String TAG = "rustAppVideoFrag";

    private Button mCaptureBtn;
    private CameraPreview mCameraPreview;

    public static VideoRecordFragment newInstance() {
        return new VideoRecordFragment();
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "frag onCreate");
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        Log.d(TAG, "frag onCreateView");
        return inflater.inflate(R.layout.frag_video_record, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        Log.d(TAG, "frag onViewCreated");
        super.onViewCreated(view, savedInstanceState);
        mCaptureBtn = view.findViewById(R.id.capture_btn);
        //mCaptureBtn.setOnClickListener(mOnClickListener);// 錄製鍵
 

        mCameraPreview = new CameraPreview(getContext());
        FrameLayout preview = view.findViewById(R.id.camera_preview);
        preview.addView(mCameraPreview);
    }
}
/<code>

使用MediaRecorder錄製給MediaRecorder指定參數後，調用start()開始錄製，stop()結束錄製

錄製開始前，獲取camera，mCamera.unlock()解鎖；錄製完畢後，清除MediaRecorder，mCamera.lock()

<code>private MediaRecorder mMediaRecorder;
    public boolean startRecording() {
        if (prepareVideoRecorder()) {
            mMediaRecorder.start();
            return true;
        } else {
            releaseMediaRecorder();
        }
        return false;
    }

    public void stopRecording() {
        if (mMediaRecorder != null) {
            mMediaRecorder.stop();
        }
        releaseMediaRecorder();
    }

    public boolean isRecording() {
        return mMediaRecorder != null;
    }

    private boolean prepareVideoRecorder() {
        if (null == mCamera) {
            mCamera = getCameraInstance();
        }
        mMediaRecorder = new MediaRecorder();

        mCamera.unlock();
        mMediaRecorder.setCamera(mCamera);

        mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
        mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);

        mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH)); 


        mMediaRecorder.setVideoSize(mOptVideoWidth, mOptVideoHeight);
        mMediaRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString());
        mMediaRecorder.setPreviewDisplay(mHolder.getSurface());

        try {
            mMediaRecorder.prepare();
        } catch (IllegalStateException e) {
            Log.d(TAG, "IllegalStateException preparing MediaRecorder: " + e.getMessage());
            releaseMediaRecorder();
            return false;
        } catch (IOException e) {
            Log.d(TAG, "IOException preparing MediaRecorder: " + e.getMessage());
            releaseMediaRecorder();
            return false;
        }
        return true;
    }

    private void releaseMediaRecorder() {
        if (mMediaRecorder != null) {
            mMediaRecorder.reset();
            mMediaRecorder.release();
            mMediaRecorder = null;
            mCamera.lock();
        }
    }

    private File getOutputMediaFile(int type) {
        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_PICTURES), TAG);
        if (!mediaStorageDir.exists()) {
            if (!mediaStorageDir.mkdirs()) {
                Log.d(TAG, "failed to create directory");
                return null;
            }
        }
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.CHINA).format(new Date());
        File mediaFile;
        if (type == MEDIA_TYPE_IMAGE) {
            mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                    "IMG_" + timeStamp + ".jpg");
            outputMediaFileType = "image/*";
        } else if (type == MEDIA_TYPE_VIDEO) {
            mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                    "VID_" + timeStamp + ".mp4");
            outputMediaFileType = "video/*";
        } else {
            return null;
        } 

        outputMediaFileUri = Uri.fromFile(mediaFile);
        return mediaFile;
    }
/<code>

後臺返回時預覽黑屏的問題CameraPreview是我們在Fragment創建時實例化並添加進去的。應用退到後臺後，CameraPreview已經被銷燬。應用回到前臺時，我們應該在onResume方法中進行操作。恢復CameraPreview。

在Fragment中，判斷銷燬和重建預覽的時機。

<code>@Override
public void onPause() {
    super.onPause();
    Log.d(TAG, "onPause: 銷燬預覽");
    mCameraPreview = null;
}

@Override
public void onResume() {
    super.onResume();
    Log.d(TAG, "onResume: 回到前臺");
    if (null == mCameraPreview) {
        initCameraPreview();
    }
}

private void initCameraPreview() {
    mCameraPreview = new CameraPreview(getContext());
    FrameLayout preview = mRoot.findViewById(R.id.camera_preview);
    preview.addView(mCameraPreview);
}
/<code>

原創作者：CHSmile，原文鏈接：https://www.jianshu.com/p/b6386ba20d08

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關鍵字: 封包 編碼 Android