几个月前尝试过这个之后,我发现让它工作的唯一可靠方法是在 AVMutableCompositionTrack 中使用一个简短的空白视频,然后用所需的图层覆盖它。
大约一个月前,由于模拟器中的错误,我将一个项目上传到 GitHub。您可以下载空白视频here https://github.com/bshamblen/VideoWatermarkBugExample,如果你愿意的话。
-(void)exportVideo
{
CGSize renderingSize = CGSizeMake(640, 360); // The desired size of your video
float displayDuration = 2.0f; //The duration of the desired video, in seconds
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *myPathDocs = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"FinalVideo-%d.mov",arc4random() % 1000]];
NSURL *url = [NSURL fileURLWithPath:myPathDocs];
NSError *error;
[[NSFileManager defaultManager] removeItemAtURL:url error:&error];
mutableComposition = [AVMutableComposition composition];
mutableCompositionVideoTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.renderSize = renderingSize;
videoComposition.frameDuration = CMTimeMake(1, 30);
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoComposition.renderSize.width, videoComposition.renderSize.height);
videoLayer.frame = CGRectMake(0, 0, videoComposition.renderSize.width, videoComposition.renderSize.height);
[parentLayer addSublayer:videoLayer];
videoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
NSString *path = [[NSBundle mainBundle] pathForResource:@"blank_1080p" ofType:@"mp4"];
NSURL *trackUrl = [NSURL fileURLWithPath:path];
AVAsset *asset = [AVAsset assetWithURL:trackUrl];
AVAssetTrack *track = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[mutableCompositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,CMTimeMakeWithSeconds(displayDuration, 600)) ofTrack:track atTime:kCMTimeZero error:nil];
CALayer *imageLayer = [CALayer layer];
imageLayer.bounds = parentLayer.frame;
imageLayer.anchorPoint = CGPointMake(0.5, 0.5);
imageLayer.position = CGPointMake(CGRectGetMidX(imageLayer.bounds), CGRectGetMidY(imageLayer.bounds));
imageLayer.backgroundColor = [UIColor blueColor].CGColor;
imageLayer.contentsGravity = kCAGravityResizeAspectFill;
[parentLayer addSublayer:imageLayer];
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(displayDuration, 600));
videoComposition.instructions = @[instruction];
exporter = [[AVAssetExportSession alloc] initWithAsset:mutableComposition presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL = url;
exporter.videoComposition = videoComposition;
exporter.outputFileType= AVFileTypeMPEG4;
exporter.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(displayDuration, 600));
exporter.shouldOptimizeForNetworkUse = YES;
[exporter exportAsynchronouslyWithCompletionHandler:^(void){
dispatch_async(dispatch_get_main_queue(), ^{
[self exportDidFinish:exporter];
});
}];
}