嘿大家我正在裁剪从iPhone上的相机拍摄的视频然后裁剪它像这样播放它。当我这样做的时候，我在视频的底部和右侧有一条奇怪的绿线？不确定为什么会发生这种情况或如何解决它。这是我如何裁剪。
- (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;
}
然后我就这样玩并调用这种作物。
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];
如果你想测试一下，只需要复制和粘贴代码然后设置一个视频，你就会看到我在说什么。
感谢您抽出宝贵时间来帮助我，我知道这是一段相当多的代码。
答案 0 :(得分：9)
iOS编码器或视频格式本身有宽度要求。尝试使宽度均匀或可被4整除。
我不知道对身高有类似的要求，但这也值得一试。
我从未发现它有记录，但要求均匀度有一定意义，因为h.264使用4：2：0 yuv颜色空间，其中UV分量是一半大小（两个维度） Y频道，具有视频的整体尺寸。如果这些尺寸不均匀，则UV尺寸不会是整数。
P.S。在这些情况下的提示是神秘的绿色。我认为它对应于YUV中的0,0,0。
答案 1 :(得分：5)
@Rhythmic的答案救了我的一天。
在我的应用中，我需要根据屏幕宽度大小的方形视频。因此对于iPhone 5来说这是320像素，而对于iPhone 6来说，它变成了375像素。
所以我遇到了iPhone 6尺寸分辨率相同的绿线问题。 因为它的屏幕尺寸宽度是375像素。并且不能被2或者整除 4。
为此，我们做了这些改变
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);
希望这会有所帮助。只需再添加一个像素，使其可以被2或4整除。
由于