Crop video in iOS see weird green line around video

Question

Hey everyone I am cropping a video taken from the camera on iPhone and then cropping it an playing it back like this. When i do it however I get a weird green line around th

Answer 1

There are width requirements for either the iOS encoders or the video format itself. Try making your width even or divisible by 4.

I wasn't aware of there being a similar requirement for height, but that could be worth a try too.

I've never found it documented, but requiring evenness makes a certain amount of sense as h.264 uses a 4:2:0 yuv colour space, where the UV component is half the size (in both dimensions) of the Y channel, which has the overall dimensions of the video. If those dimensions weren't even, the UV dimensions wouldn't be integral.

p.s. the hint in these cases is the mysterious green colour. I think it corresponds to 0, 0, 0 in YUV.

Answer 2

The answer by @Rhythmic saved my day.

In my app, I need square video as per screen width size. So for iPhone 5 this comes 320 pixels and for iPhone 6 this becomes 375 pixels.

So I came across same green line issue for iPhone 6 size resolution. Because its screen size width is 375 pixels. And not divisible by 2 or 4.

To come out of this we made these changes

 AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition];
    MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction];
    MainInstruction.timeRange = range;

    MainCompositionInst.frameDuration = VideoFrameDuration; //Constants
    MainCompositionInst.renderScale = VideoRenderScale; //Constants

    if ((int)SCREEN_WIDTH % 2 == 0)
        MainCompositionInst.renderSize = CGSizeMake(SCREEN_WIDTH, SCREEN_WIDTH);
    else // This does the trick
        MainCompositionInst.renderSize = CGSizeMake(SCREEN_WIDTH+1, SCREEN_WIDTH+1); 

Hope This helps. Just add one more pixel to it so it becomes divisible by 2 or 4.

Thanks