MediaMetadataRetriever.getFrameAtTime（）只返回第一帧 [英] MediaMetadataRetriever.getFrameAtTime() returns only first frame

问题描述

我已经提取使用MetadataRetriever一个视频帧，并保存所有图像在的ArrayList＆LT;位图＆GT; 。我想存储所有的人都在SD卡（只用于测试目的）。

I have extracted frames from a video using MetadataRetriever, and have stored all images in an ArrayList<Bitmap>. I want to store all of them on an SD card (just for testing purposes).

但是，当我拿出一个文件夹从仿真器，并期待在保存的图像，所有的图像视频的第一帧而已。

But when I pull out a folder from the emulator and look at the saved images, all images were of the video's first frame only.

这是我从视频中提取帧：

This is how I extract the frames from the video:

File videoFile=new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/videos","sample_mpeg4.mp4");

Uri videoFileUri=Uri.parse(videoFile.toString());

MediaMetadataRetriever retriever = new MediaMetadataRetriever();
retriever.setDataSource(videoFile.getAbsolutePath());
ArrayList<Bitmap> rev=new ArrayList<Bitmap>();

//Create a new Media Player
MediaPlayer mp = MediaPlayer.create(getBaseContext(), videoFileUri);

int millis = mp.getDuration();
for(int i=0;i<millis;i+=100){
   Bitmap bitmap=retriever.getFrameAtTime(i,OPTION_CLOSEST_SYNC);
   rev.add(bitmap);
}

这是我如何保存它们（我调用这个方法并传递位图的ArrayList）：

And this is how I'm saving them (I'm calling this method and passing the bitmap ArrayList):

public void saveFrames(ArrayList<Bitmap> saveBitmapList) throws IOException{
    Random r = new Random();
    int folder_id = r.nextInt(1000) + 1;

    String folder = Environment.getExternalStorageDirectory()+"/videos/frames/"+folder_id+"/";
    File saveFolder=new File(folder);
    if(!saveFolder.exists()){
       saveFolder.mkdirs();
    }

    int i=1;
    for (Bitmap b : saveBitmapList){
       ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        b.compress(Bitmap.CompressFormat.JPEG, 40, bytes);

        File f = new File(saveFolder,("frame"+i+".jpg"));

        f.createNewFile();

        FileOutputStream fo = new FileOutputStream(f);
        fo.write(bytes.toByteArray());

           fo.flush();
           fo.close();

        i++;
    }
    Toast.makeText(getApplicationContext(),"Folder id : "+folder_id, Toast.LENGTH_LONG).show();

}

当我拉出来一个文件夹以查看所有的帧，所有图像都是视频的第一帧。可有人请向我解释发生了什么事？

When I pull out a folder to see all frames, all of the images were of the first frame of video. Can someone please explain to me what is happening?

更新：

我试图用另一段视频。我发现，我没有收到空白图像，但它永远只能返回第一帧。

I've tried with another video. I've found that I'm not getting blank images, but it's always returning the first frame only.

MediaMetadataRetriever.getFrameAtTime（长timeUS）是只返回第一帧，但我想要检索的所有帧。我应该什么样的变化？

MediaMetadataRetriever.getFrameAtTime(long timeUS) is returning only the first frame, but I want to retrieve all frames. What changes should I make?

我要如何解决呢？

推荐答案

类MediaMetadataRetriever 的 getFrameAt 方法接受微秒代替毫秒（第二1 /第百万），所以在你的情况下，它总是舍入下到第一帧

MediaMetadataRetriever's getFrameAt method takes in microseconds (1/1000000th of a second) instead of milliseconds, so in your case it is always rounding down to the 1st frame.

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