我正在使用Android vision API中的FaceTracker示例。但是，我在录制视频时遇到了困难，同时在它们上面绘制了叠加层。
一种方法是将位图存储为图像并使用FFmpeg或Xuggler将它们合并为视频，但我想知道如果我们可以在预计投影时在运行时录制视频，是否有更好的解决方案。
更新1：我使用媒体记录器更新了following类，但录制仍然无法正常工作。当我调用triggerRecording（）函数时抛出以下错误：
MediaRecorder：以无效状态调用：4
我在清单文件中有外部存储权限。
更新2：
我在代码中修复了上述问题，并在onSurfaceCreated回调中移动了setupMediaRecorder（）。但是，当我停止录制时，它会抛出运行时异常。根据documentation，如果没有视频/音频数据，将抛出运行时异常。
那么，我在这里错过了什么？
public class CameraSourcePreview extends ViewGroup {
private static final String TAG = "CameraSourcePreview";
private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
static {
ORIENTATIONS.append(Surface.ROTATION_0, 90);
ORIENTATIONS.append(Surface.ROTATION_90, 0);
ORIENTATIONS.append(Surface.ROTATION_180, 270);
ORIENTATIONS.append(Surface.ROTATION_270, 180);
}
private MediaRecorder mMediaRecorder;
/**
* Whether the app is recording video now
*/
private boolean mIsRecordingVideo;
private Context mContext;
private SurfaceView mSurfaceView;
private boolean mStartRequested;
private boolean mSurfaceAvailable;
private CameraSource mCameraSource;
private GraphicOverlay mOverlay;
public CameraSourcePreview(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
mStartRequested = false;
mSurfaceAvailable = false;
mSurfaceView = new SurfaceView(context);
mSurfaceView.getHolder().addCallback(new SurfaceCallback());
addView(mSurfaceView);
mMediaRecorder = new MediaRecorder();
}
private void setUpMediaRecorder() throws IOException {
mMediaRecorder.setPreviewDisplay(mSurfaceView.getHolder().getSurface());
mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
mMediaRecorder.setOutputFile(Environment.getExternalStorageDirectory() + File.separator + Environment.DIRECTORY_DCIM + File.separator + System.currentTimeMillis() + ".mp4");
mMediaRecorder.setVideoEncodingBitRate(10000000);
mMediaRecorder.setVideoFrameRate(30);
mMediaRecorder.setVideoSize(480, 640);
mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
//int rotation = mContext.getWindowManager().getDefaultDisplay().getRotation();
//int orientation = ORIENTATIONS.get(rotation);
mMediaRecorder.setOrientationHint(ORIENTATIONS.get(0));
mMediaRecorder.prepare();
mMediaRecorder.setOnErrorListener(new MediaRecorder.OnErrorListener() {
@Override
public void onError(MediaRecorder mr, int what, int extra) {
Timber.d(mr.toString() + " : what[" + what + "]" + " Extras[" + extra + "]");
}
});
}
public void start(CameraSource cameraSource) throws IOException {
if (cameraSource == null) {
stop();
}
mCameraSource = cameraSource;
if (mCameraSource != null) {
mStartRequested = true;
startIfReady();
}
}
public void start(CameraSource cameraSource, GraphicOverlay overlay) throws IOException {
mOverlay = overlay;
start(cameraSource);
}
public void stop() {
if (mCameraSource != null) {
mCameraSource.stop();
}
}
public void release() {
if (mCameraSource != null) {
mCameraSource.release();
mCameraSource = null;
}
}
private void startIfReady() throws IOException {
if (mStartRequested && mSurfaceAvailable) {
mCameraSource.start(mSurfaceView.getHolder());
if (mOverlay != null) {
Size size = mCameraSource.getPreviewSize();
int min = Math.min(size.getWidth(), size.getHeight());
int max = Math.max(size.getWidth(), size.getHeight());
if (isPortraitMode()) {
// Swap width and height sizes when in portrait, since it will be rotated by
// 90 degrees
mOverlay.setCameraInfo(min, max, mCameraSource.getCameraFacing());
} else {
mOverlay.setCameraInfo(max, min, mCameraSource.getCameraFacing());
}
mOverlay.clear();
}
mStartRequested = false;
}
}
private class SurfaceCallback implements SurfaceHolder.Callback {
@Override
public void surfaceCreated(SurfaceHolder surface) {
mSurfaceAvailable = true;
surface.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
// setup the media recorder
try {
setUpMediaRecorder();
} catch (IOException e) {
e.printStackTrace();
}
try {
startIfReady();
} catch (IOException e) {
Timber.e(TAG, "Could not start camera source.", e);
}
}
@Override
public void surfaceDestroyed(SurfaceHolder surface) {
mSurfaceAvailable = false;
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
int width = 320;
int height = 240;
if (mCameraSource != null) {
Size size = mCameraSource.getPreviewSize();
if (size != null) {
width = size.getWidth();
height = size.getHeight();
}
}
// Swap width and height sizes when in portrait, since it will be rotated 90 degrees
if (isPortraitMode()) {
int tmp = width;
width = height;
height = tmp;
}
final int layoutWidth = right - left;
final int layoutHeight = bottom - top;
// Computes height and width for potentially doing fit width.
int childWidth = layoutWidth;
int childHeight = (int) (((float) layoutWidth / (float) width) * height);
// If height is too tall using fit width, does fit height instead.
if (childHeight > layoutHeight) {
childHeight = layoutHeight;
childWidth = (int) (((float) layoutHeight / (float) height) * width);
}
for (int i = 0; i < getChildCount(); ++i) {
getChildAt(i).layout(0, 0, childWidth, childHeight);
}
try {
startIfReady();
} catch (IOException e) {
Timber.e(TAG, "Could not start camera source.", e);
}
}
private boolean isPortraitMode() {
int orientation = mContext.getResources().getConfiguration().orientation;
if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
return false;
}
if (orientation == Configuration.ORIENTATION_PORTRAIT) {
return true;
}
Timber.d(TAG, "isPortraitMode returning false by default");
return false;
}
private void startRecordingVideo() {
try {
// Start recording
mMediaRecorder.start();
mIsRecordingVideo = true;
} catch (IllegalStateException e) {
e.printStackTrace();
}
}
private void stopRecordingVideo() {
// UI
mIsRecordingVideo = false;
// Stop recording
mMediaRecorder.stop();
mMediaRecorder.reset();
}
public void triggerRecording() {
if (mIsRecordingVideo) {
stopRecordingVideo();
Timber.d("Recording stopped");
} else {
startRecordingVideo();
Timber.d("Recording starting");
}
}
}
解决方案1：从Android Lollipop开始，引入了MediaProjection API，它与MediaRecorder一起用于将SurfaceView保存到视频文件中。 This example shows how to output a SurfaceView to a video file.
解决方案2：或者，您可以使用Grafika repository中提供的一个简洁的编码器类。请注意，这将要求您移植FaceTracker应用程序，以便它使用OpenGL执行所有渲染。这是因为Grafika样本利用OpenGL管道来快速读取和写入纹理数据。
有一个最小的例子可以在CircularEncoder类中使用ContinuousCaptureActivity完全达到你想要的效果。这提供了Frame Blitting的示例，同时向屏幕显示帧缓冲数据并输出到视频。
主要的变化是使用Grafika WindowSurface而不是用于FaceTracker应用程序的SurfaceView，这将设置EGL上下文，允许您通过编码器将帧缓冲区数据保存到文件中。一旦你可以将所有内容渲染到WindowSurface，以与ContinuousCaptureActivity类相同的方式设置记录是微不足道的。