ios – 将AVMutableVideoComposition的文本叠加添加到特定的时间

发布时间：2020-12-15 01:45:28 所属栏目：百科来源：网络整理

导读：我找到了一些示例,说明如何在视频上添加文本叠加层. Ray的教程 – http://www.raywenderlich.com/30200/avfoundation-tutorial-adding-overlays-and-animations-to-videos 这个答案 – How can I add a watermark in a captured video on iOS 我还引用了其他

我找到了一些示例,说明如何在视频上添加文本叠加层.

Ray的教程 – http://www.raywenderlich.com/30200/avfoundation-tutorial-adding-overlays-and-animations-to-videos

这个答案 – How can I add a watermark in a captured video on iOS

我还引用了其他几个.我的代码看起来与答案几乎相同,我一直试图调整它以使文本覆盖仅在视频开头显示一两秒钟.有关如何实现这一目标的任何帮助？

这是我的代码.这样可以导出视频,并在整个持续时间内显示叠加层.

if(vA) {
    videoCompositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    [videoCompositionTrack insertTimeRange:videoTimerange ofTrack:[[vA tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:&error];
    [videoCompositionTrack setPreferredTransform:[[[vA tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];
    if(error)
        NSLog(@"%@",error);
}

if(aA) {
    audioCompositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    [audioCompositionTrack insertTimeRange:audioTimerange ofTrack:[[aA tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:&error];
    if(error)
        NSLog(@"%@",error);
}

CGSize videoSize = [videoCompositionTrack naturalSize];

UIImage *myImage = [UIImage imageNamed:@"cover.png"];
CALayer *aLayer = [CALayer layer];
aLayer.contents = (id)myImage.CGImage;
aLayer.frame = CGRectMake(5,25,100,56);
aLayer.opacity = 0.7;

CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.string = titleText;
titleLayer.fontSize = 18;
titleLayer.foregroundColor = titleColor.CGColor;
titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.frame = CGRectMake(20,10,videoSize.width - 40,20);
[titleLayer displayIfNeeded];

CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0,videoSize.width,videoSize.height);
videoLayer.frame = CGRectMake(0,videoSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:aLayer];
if(titleText && [titleText length] > 0) {
    [parentLayer addSublayer:titleLayer];
}

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

AVAssetTrack *videoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
[instruction setTimeRange:CMTimeRangeMake(kCMTimeZero,[mixComposition duration])];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
videoComp.instructions = [NSArray arrayWithObject:instruction];

AVAssetExportSession *_assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
_assetExport.videoComposition = videoComp;
_assetExport.outputFileType = AVFileTypeMPEG4;
_assetExport.outputURL = outputFileUrl;

[_assetExport exportAsynchronouslyWithCompletionHandler:^{
    AVAssetExportSessionStatus status = [_assetExport status];
    switch (status) {
        case AVAssetExportSessionStatusFailed:
            NSLog(@"Export Failed");
            NSLog(@"Export Error: %@",[_assetExport.error localizedDescription]);
            NSLog(@"Export Error Reason: %@",[_assetExport.error localizedFailureReason]);
            break;
        case AVAssetExportSessionStatusCompleted:
            NSLog(@"Export Completed");
            [self performSelectorOnMainThread:@selector(updateProgressIndicator:) withObject:[NSNumber numberWithFloat:2] waitUntilDone:YES];
            break;
        case AVAssetExportSessionStatusUnknown:
            NSLog(@"Export Unknown");
            break;
        case AVAssetExportSessionStatusExporting:
            NSLog(@"Export Exporting");
            break;
        case AVAssetExportSessionStatusWaiting:
            NSLog(@"Export Waiting");
            break;
    }
}];

解决方法

我想出了我需要做什么.真的没什么特别的.它只需要更好地理解所有可能的东西.

基本上我所要做的就是在图层中添加一个基本的不透明度动画,其中包含文本.

// My original code for creating the text layer
CATextLayer *titleLayer = [CATextLayer layer];
.
.
.
[titleLayer displayIfNeeded];

// the code for the opacity animation which then removes the text
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
[animation setDuration:0];
[animation setFromValue:[NSNumber numberWithFloat:1.0]];
[animation setToValue:[NSNumber numberWithFloat:0.0]];
[animation setBeginTime:1];
[animation setRemovedOnCompletion:NO];
[animation setFillMode:kCAFillModeForwards];
[titleLayer addAnimation:animation forKey:@"animateOpacity"];

（编辑：李大同）

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