在ios目标c中的视频上添加水印时出错答案

【问题标题】：Getting Error when adding watermark on video in ios objective c在ios目标c中的视频上添加水印时出错
【发布时间】：2017-01-26 11:35:21
【问题描述】：

导出文件时出现此错误

Error Domain=AVFoundationErrorDomain Code=-11800 "操作无法完成" UserInfo={NSUnderlyingError=0x608000642310 {Error Domain=NSOSStatusErrorDomain Code=-12120 "(null)"}

AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:url options:nil];

AVMutableComposition* miComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [miComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject;
AVMutableCompositionTrack *compositionAudioTrack = [miComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipAudioTrack = [videoAsset tracksWithMediaType:AVMediaTypeAudio].firstObject;
//If you need audio as well add the Asset Track for audio here

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [videoAsset duration]) ofTrack:clipVideoTrack atTime:kCMTimeZero error:nil];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [videoAsset duration]) ofTrack:clipAudioTrack atTime:kCMTimeZero error:nil];

[compositionVideoTrack setPreferredTransform:[[videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject preferredTransform]];



CGSize sizeOfVideo=[clipVideoTrack naturalSize];



//Image of watermark
UIImage *myImage=[UIImage imageNamed:@"_minutestory.png"];
CALayer *layerCa = [CALayer layer];
layerCa.contents = (id)myImage.CGImage;
layerCa.frame = CGRectMake((sizeOfVideo.width - 100),20 , 100, 100);
layerCa.opacity = 0.6;

CALayer *optionalLayer=[CALayer layer];

optionalLayer.frame=CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
[optionalLayer setMasksToBounds:YES];

CALayer *parentLayer=[CALayer layer];
CALayer *videoLayer=[CALayer layer];
parentLayer.frame=CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
videoLayer.frame=CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:optionalLayer];
[parentLayer addSublayer:layerCa];

AVMutableVideoComposition *videoComposition=[AVMutableVideoComposition videoComposition] ;
videoComposition.frameDuration=CMTimeMake(1, 30);
videoComposition.renderSize=sizeOfVideo;
videoComposition.animationTool=[AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [miComposition duration]);
AVAssetTrack *vidTrack = [[miComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:vidTrack];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
videoComposition.instructions = [NSArray arrayWithObject: instruction];

[[NSFileManager defaultManager] removeItemAtPath:url error:NULL];

exporter2 =
[[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
exporter2.videoComposition = videoComposition;

exporter2.outputURL=url;
exporter2.outputFileType = AVFileTypeMPEG4;
exporter2.shouldOptimizeForNetworkUse = YES;




exportProgressBarTimer = [NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(updateExportDisplay) userInfo:nil repeats:YES];

[exporter2 exportAsynchronouslyWithCompletionHandler:^{
    dispatch_async(dispatch_get_main_queue(), ^{
        [self exportFinish:exporter2];


    });
}];

【问题讨论】：

欢迎来到 Stack Overflow！为了给您一个很好的答案，如果您还没有看过How to Ask，它可能会对我们有所帮助。如果您可以提供minimal reproducible example，它可能也很有用。
这个错误的描述性不是很强，但它的意思是你正在给组合一个它不知道如何完成的指令。尝试通过注释掉代码的各个部分来缩小错误发生的范围，直到您获得工作视频，然后将它们重新添加。您正在做的事情通常在图层说明中没有“意义” - 你会有不正确的帧、错误的开始时间、重叠的指令，诸如此类。

标签： ios objective-c avfoundation watermark

【解决方案1】：

首先，也许您应该使用另一个 url 作为导出器的 outputURL，上面的代码使用 AVURLAsset 的源 url 作为导出器的 outputURL，并基于您在导出之前删除 url 处的文件（这意味着您删除了用于导出的源资产），你不可能实现你的目标。
顺便说一句，如果你想删除基于 url 的文件。你应该使用

[[NSFileManager defaultManager] removeItemAtURL:url error:nil];

改为。

【讨论】：