MediaMetadataRetriever .getFrameAtTime(long, option) crashing

Question

I've got a loop where I'm trying to extract a frame from a video every 1/10th of a second. But after 19 frames (1.9s of the video), I get the following error on Logcat:

01-22 11:59:15.498: E/OMXCodec(38): [OMX.google.h264.decoder] Timed out waiting for output buffers: 0/0
01-22 11:59:15.598: E/MetadataRetrieverClient(38): failed to capture a video frame
01-22 11:59:15.598: E/MediaMetadataRetrieverJNI(572): getFrameAtTime: videoFrame is a NULL pointer
01-22 11:59:15.598: D/AndroidRuntime(572): Shutting down VM
01-22 11:59:15.598: W/dalvikvm(572): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
01-22 11:59:15.608: E/AndroidRuntime(572): FATAL EXCEPTION: main
01-22 11:59:15.608: E/AndroidRuntime(572): java.lang.NullPointerException

This is the code I'm using:

File videoPath = new File(Environment.getExternalStorageDirectory(), "test.mp4");
String video = videoPath.getAbsolutePath();
MediaMetadataRetriever vidFile = new MediaMetadataRetriever();
vidFile.setDataSource(video);

//Create folder to store images
String storageFolder = "/Storage";
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File newFolder = new File(extStorageDirectory + storageFolder);
newFolder.mkdir();

String value = vidFile.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
long vidLength = (Long.parseLong(value)/1000); //Returns milliseconds - divide by 1,000
//Video length = 30037ms - result is 30.037s

for(int i = 0; i <= 10*vidLength; i++, image++) //10*vidLength since I'm getting frames every 1/10th sec
{
    Bitmap bmp = vidFile.getFrameAtTime(100000*i, MediaMetadataRetriever.OPTION_CLOSEST);
    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    bmp.compress(Bitmap.CompressFormat.PNG, 100, bytes);
    String imagename = String.format(Locale.ENGLISH, "%03d", image);
    File f = new File(Environment.getExternalStorageDirectory() + storageFolder + File.separator + imagename + ".png");
    f.createNewFile();
    FileOutputStream fo = new FileOutputStream(f);
    fo.write(bytes.toByteArray());
    fo.close();

    //Don't seem to make a difference one way or the other
    bytes.flush(); 
    bytes.close();  
}

Like I said, it should get ~300 frames, but only manages to extract 19 frames before crashing, but I don't see why the NULL pointer error is happening.

Thanks in advance

Answer 1

Have you tried using FFmpegMediaMetadataRetriever lib instead of MediaMetadataRetriever?

Also, from this line on your logcat:

01-22 11:59:15.598: E/MediaMetadataRetrieverJNI(572): getFrameAtTime: videoFrame is a NULL pointer

I would try making it log every line of the for loop, like Log.d("MyApp","Param of getFrameAtTime"+(100000*i));

I know you already know which frame is the problem (19/20), but just to see what happens with that variable before becoming a null pointer (maybe you could work with Long i instead of int i?).

Also, did you try the suggestion above to use MediaMetadataRetriever.OPTION_CLOSEST_SYNC instead of OPTION_CLOSEST?

Answer 2

I get similar behavior on my Evo V running Android 4.0: the first six frames of my test video convert just fine, then I start getting null pointers back, even if I construct a new MediaMetadataRetriever to try again.

My logs also show: "MediaMetadataRetriever server died!"

There is a way to avoid this problem and depending on what you are trying to do it may be suitable: pass MediaMetadataRetriever.OPTION_CLOSEST_SYNC instead of OPTION_CLOSEST.

In my tests, the crashes always go away when I use OPTION_CLOSEST_SYNC.

This is not much help for my application, because I actually do need frames at very close intervals, not just the designated "sync frames." But it may be more acceptable in yours.