How does Instagram crop video in android app?

问题:

I am trying to record the video in 1:1 ratio (square) and i cant get it to work, if i set custom resolution in media recorder instance i get an error on media recorder start.

mediaRecorder.setVideoSize(480, 480);

but it works if i set the resolution supported by camera.

Camera.Parameters p = c.getParameters();
        List<Camera.Size> list = p.getSupportedPreviewSizes();
        //They are ordered from largest to smallest, so the largest will be...
        for (Camera.Size i : list) {
            if (i.width <= 640 && i.width >= 480) {
                size = i;
            }
            Log.d(TAG, "i.height: " + i.height + " i.width" + i.width);
        }
        if (size != null) {
            p.setPreviewSize(size.width, size.height);
            c.setParameters(p);
        }

then set

 mediaRecorder.setVideoSize(size.width, size.height);

I usually get 480 by 640. Is there a way to crop the video on android? I have seen ffmpeg library but i need to use this in project and i am not sure how LGPL works. Is there a simpler solution to this?

回答1:

Actually just adding this dependency:

compile 'com.writingminds:FFmpegAndroid:0.3.2'

then using below code makes the thing. Only problem is, it's not so fast. In my tests, 20sec length 720x480 video cropped to 480x in 6-7 second with a galaxy s6.

FFmpeg ffmpeg = FFmpeg.getInstance(context);
String[] complexCommand = {"-y", "-i", originalFilePath, "-vf", "crop=480:480:80:0", "-preset", "ultrafast", "-strict", "-2", "-c:v", "libx264", "-c:a", "copy", originalFilePath.replace(".mp4", "_crop.mp4")};
try {
    ffmpeg.execute(complexCommand, new ExecuteBinaryResponseHandler() {
        @Override
        public void onStart() {super.onStart();}

        @Override
        public void onSuccess(String message) {super.onSuccess(message);}

        @Override
        public void onProgress(String message) {super.onProgress(message);}

        @Override
        public void onFailure(String message) {super.onFailure(message);}

        @Override
        public void onFinish() {super.onFinish();}
    });
} catch (FFmpegCommandAlreadyRunningException e) {
    Log.e("ffmpeg", "ffmpeg already running");
}

There's another better solution using with new MediaCodec if your min sdk is api 18

回答2:

1. You can take a look at https://github.com/boxme/SquareCamera. It's used to crop a image, but the idea can be used to crop a video. The main idea is to add a black cover top and bottom(or left and right)to make it seemed like a square.
2. FFmpeg can be used, of course, though it is a little complicated.

回答3:

Using OpenGL and shader can solve this problem. Or you can use libyuv to do it on CPU.