Crop video in iOS see weird green line around video - ios

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 the bottom and right side of the video? Not sure why this is happening or how to fix it. Here is how I am cropping.
- (UIImageOrientation)getVideoOrientationFromAsset:(AVAsset *)asset
{
AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
CGSize size = [videoTrack naturalSize];
CGAffineTransform txf = [videoTrack preferredTransform];
if (size.width == txf.tx && size.height == txf.ty)
return UIImageOrientationLeft; //return UIInterfaceOrientationLandscapeLeft;
else if (txf.tx == 0 && txf.ty == 0)
return UIImageOrientationRight; //return UIInterfaceOrientationLandscapeRight;
else if (txf.tx == 0 && txf.ty == size.width)
return UIImageOrientationDown; //return UIInterfaceOrientationPortraitUpsideDown;
else
return UIImageOrientationUp; //return UIInterfaceOrientationPortrait;
}
- (AVAssetExportSession*)applyCropToVideoWithAsset:(AVAsset*)asset AtRect:(CGRect)cropRect OnTimeRange:(CMTimeRange)cropTimeRange ExportToUrl:(NSURL*)outputUrl ExistingExportSession:(AVAssetExportSession*)exporter WithCompletion:(void(^)(BOOL success, NSError* error, NSURL* videoUrl))completion
{
// NSLog(#"CALLED");
//create an avassetrack with our asset
AVAssetTrack *clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
//create a video composition and preset some settings
AVMutableVideoComposition* videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.frameDuration = CMTimeMake(1, 30);
CGFloat cropOffX = cropRect.origin.x;
CGFloat cropOffY = cropRect.origin.y;
CGFloat cropWidth = cropRect.size.width;
CGFloat cropHeight = cropRect.size.height;
// NSLog(#"width: %f - height: %f - x: %f - y: %f", cropWidth, cropHeight, cropOffX, cropOffY);
videoComposition.renderSize = CGSizeMake(cropWidth, cropHeight);
//create a video instruction
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = cropTimeRange;
AVMutableVideoCompositionLayerInstruction* transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];
UIImageOrientation videoOrientation = [self getVideoOrientationFromAsset:asset];
CGAffineTransform t1 = CGAffineTransformIdentity;
CGAffineTransform t2 = CGAffineTransformIdentity;
switch (videoOrientation) {
case UIImageOrientationUp:
t1 = CGAffineTransformMakeTranslation(clipVideoTrack.naturalSize.height - cropOffX, 0 - cropOffY );
t2 = CGAffineTransformRotate(t1, M_PI_2 );
break;
case UIImageOrientationDown:
t1 = CGAffineTransformMakeTranslation(0 - cropOffX, clipVideoTrack.naturalSize.width - cropOffY ); // not fixed width is the real height in upside down
t2 = CGAffineTransformRotate(t1, - M_PI_2 );
break;
case UIImageOrientationRight:
t1 = CGAffineTransformMakeTranslation(0 - cropOffX, 0 - cropOffY );
t2 = CGAffineTransformRotate(t1, 0 );
break;
case UIImageOrientationLeft:
t1 = CGAffineTransformMakeTranslation(clipVideoTrack.naturalSize.width - cropOffX, clipVideoTrack.naturalSize.height - cropOffY );
t2 = CGAffineTransformRotate(t1, M_PI );
break;
default:
NSLog(#"no supported orientation has been found in this video");
break;
}
CGAffineTransform finalTransform = t2;
[transformer setTransform:finalTransform atTime:kCMTimeZero];
//add the transformer layer instructions, then add to video composition
instruction.layerInstructions = [NSArray arrayWithObject:transformer];
videoComposition.instructions = [NSArray arrayWithObject: instruction];
//Remove any prevouis videos at that path
[[NSFileManager defaultManager] removeItemAtURL:outputUrl error:nil];
if (!exporter){
exporter = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality] ;
}
// assign all instruction for the video processing (in this case the transformation for cropping the video
exporter.videoComposition = videoComposition;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
if (outputUrl){
exporter.outputURL = outputUrl;
[exporter exportAsynchronouslyWithCompletionHandler:^{
switch ([exporter status]) {
case AVAssetExportSessionStatusFailed:
NSLog(#"crop Export failed: %#", [[exporter error] localizedDescription]);
if (completion){
dispatch_async(dispatch_get_main_queue(), ^{
completion(NO,[exporter error],nil);
});
return;
}
break;
case AVAssetExportSessionStatusCancelled:
NSLog(#"crop Export canceled");
if (completion){
dispatch_async(dispatch_get_main_queue(), ^{
completion(NO,nil,nil);
});
return;
}
break;
default:
break;
}
if (completion){
dispatch_async(dispatch_get_main_queue(), ^{
completion(YES,nil,outputUrl);
});
}
}];
}
return exporter;
}
And then I play and call the crop like this.
AVAsset *assest = [AVAsset assetWithURL:self.videoURL];
NSString * documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *exportPath = [documentsPath stringByAppendingFormat:#"/croppedvideo.mp4"];
NSURL *exportUrl = [NSURL fileURLWithPath:exportPath];
AVAssetExportSession *exporter = [AVAssetExportSession exportSessionWithAsset:assest presetName:AVAssetExportPresetLowQuality];
[self applyCropToVideoWithAsset:assest AtRect:CGRectMake(self.view.frame.size.width/2 - 57.5 - 5, self.view.frame.size.height / 2 - 140, 115, 85) OnTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(assest.duration.value, 1))
ExportToUrl:exportUrl ExistingExportSession:exporter WithCompletion:^(BOOL success, NSError *error, NSURL *videoUrl) {
AVPlayer *player = [AVPlayer playerWithURL:videoUrl];
AVPlayerLayer *layer = [AVPlayerLayer playerLayerWithPlayer:player];
layer.frame = CGRectMake(125, 365, 115, 115);
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 400, 400)];
[view.layer addSublayer:layer];
[self.view addSubview:view];
[player play];
If you want to test this, the code just need to be copied and pasted and then set a video, and you will see what I am talking about.
Thanks for taking the time to help me I know it is a fair bit of code.

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);
Just add one more pixel to it so it becomes divisible by 2 or 4.