How to use setCamera (MediaRecorder)?

问题

According to Android SDK MediaRecorder.setCamera can be used to recycle the existing camera instance for video capture and preview without resetting the preview. I was not able to find any sample, and all my attempts were futile: I either get the wrong state exception, or MediaRecorder.prepare fails.

Does anyone know if this method usable at all?
How can I use it then?
Any samples available on the Web?

For reference: http://developer.android.com/reference/android/media/MediaRecorder.html#setCamera(android.hardware.Camera)

回答1:

I ran into the same problem and found out how it can work. Some things have to be done correctly. First you should check the state chart from the android document.

A working order of commands is as follows.

mCamera = Camera.open();
rec = new MediaRecorder();                               // state "Initial"

mCamera.lock();
mCamera.unlock();

rec.setCamera(mCamera);                                  // state still "Initial"
rec.setVideoSource(MediaRecorder.VideoSource.CAMERA);    // state "Initialized"
rec.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);  // state "DataSourceConfigured"
rec.setVideoEncoder(MediaRecorder.VideoEncoder.H264);

rec.setPreviewDisplay(surfaceHolder.getSurface());

rec.setOutputFile(Environment.getExternalStorageDirectory() + "/test.mp4");

rec.prepare();                                           // state "Prepared"
rec.start();                                             // state "Recording"

// ...

rec.stop();                                              // state "Initial"

A full example can be found here.

回答2:

The Android Camera app source provides the best example. After some investigation, I discovered that recorder.setCamera(camera) should be called immediately after instantiation of the MediaRecorder, or at least before any settings are applied to it. Applying any settings (setVideoSource(), etc.) before calling setCamera() results in an error.

回答3:

I got hint from @lyron.

First, open the front camera.

    int cameraId = -1;
    int camNums = Camera.getNumberOfCameras();

    for( int i = 0 ; i < camNums ; i++) {
        CameraInfo info = new CameraInfo();
        Camera.getCameraInfo(i, info);
        if( info.facing == CameraInfo.CAMERA_FACING_FRONT ) {
            cameraId = i;
            break;
        }
    }
    mCamera = Camera.open(cameraId);
    mCamera.unlock();

I need to use the front camera as above.

And DON'T FORGET to UNLOCK the camera.

If you don't, you'll see errors below.

E/MediaRecorder(15509): start failed: -19
E/SampleVideoRecorder(15509): Exception : 
E/SampleVideoRecorder(15509): java.lang.RuntimeException: start failed.
E/SampleVideoRecorder(15509):   at android.media.MediaRecorder.start(Native Method)

Second, set the camera before setting the others like this.

                recorder = new MediaRecorder();
                recorder.setCamera( mCamera );   // like this!

                recorder.setAudioSource( MediaRecorder.AudioSource.MIC);
                recorder.setVideoSource( MediaRecorder.VideoSource.CAMERA);
                recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
                recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                recorder.setVideoEncoder(MediaRecorder.VideoEncoder.MPEG_4_SP);

                recorder.setVideoSize( 2560, 1440 );
                recorder.setVideoFrameRate(30);

                recorder.setPreviewDisplay(holder.getSurface());
                recorder.setOutputFile( s_dir );

                try {
                    recorder.prepare();
                    recorder.start();
                } catch( Exception e ) {
                    Log.e("SampleVideoRecorder", "Exception : ", e );

                    recorder.release();
                    recorder = null;
                }

Someone says that setCamera() should be called before prepare().

But I'm watching my code is working.

回答4:

Have you tried to use the following functions after creating an instance of mediarecorder?

//Unlocks the camera to allow another process to access it.

mCameraDevice.unlock();

//Sets a Camera to use for recording. Use this function to switch quickly between preview and //capture mode without a teardown of the camera object.

mMediaRecorder.setCamera(mCameraDevice);

回答5:

I had my MediaRecorder initiated:

MediaRecorder mediaRecorder = null;

but not like this :

MediaRecorder mediaRecorder = new MediaRecorder();

(headbang) haha.. now my issue is a kalydascope for a preview.. time to search the interwebs..

hopefully this helped someone.

回答6:

I found 2 links you may find useful. Android Camera git repo and a MediaRecorder example

来源：https://stackoverflow.com/questions/2859458/how-to-use-setcamera-mediarecorder

标签

android

camera

mediarecorder