iphone - 如何在 iOS 中实时嵌入文本（标题）视频？

Question

我想在录制的视频中嵌入文本，然后将其保存在相机胶卷中。当此视频在任何其他设备上播放时，此文本应显示

Answer 1

从这里开始：如何在视频上添加叠加文本，然后重新编码？

请注意，这不是针对 ARC 更新的，但应该让您对该方法有一个很好的了解。此示例包括添加图像和文本，使用 iOS 7 API/CoreText 可能有更快的方法。

另外：像这样对视频进行实时合成意味着将必要的帧解压缩为位图，绘制文本，然后重新压缩视频。这是一项昂贵的操作，性能可能很差。这不是适合移动应用程序的东西。

这是在视频文件中添加文本和图像的代码。这可能会对您有所帮助。

AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:[NSURL fileURLWithPath:videoName]  options:nil];

AVMutableComposition* mixComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

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

[compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];

CGSize videoSize = [clipVideoTrack naturalSize]; 

UIImage *myImage = [UIImage imageNamed:@"29.png"];
CALayer *aLayer = [CALayer layer];
aLayer.contents = (id)myImage.CGImage;
aLayer.frame = CGRectMake(videoSize.width - 65, videoSize.height - 75, 57, 57);
aLayer.opacity = 0.65;
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
videoLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:aLayer];

CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.string = @"Text goes here";
titleLayer.font = @"Helvetica";
titleLayer.fontSize = videoSize.height / 6;
//?? titleLayer.shadowOpacity = 0.5;
titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height / 6); //You may need to adjust this for proper display
[parentLayer addSublayer:titleLayer]; //ONLY IF WE ADDED TEXT

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

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

AVAssetExportSession *assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];//AVAssetExportPresetPassthrough
assetExport.videoComposition = videoComp;

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString* VideoName = [NSString stringWithFormat:@"%@/mynewwatermarkedvideo.mp4",documentsDirectory];


 //NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:VideoName];
NSURL *exportUrl = [NSURL fileURLWithPath:VideoName];

if ([[NSFileManager defaultManager] fileExistsAtPath:VideoName])
{
    [[NSFileManager defaultManager] removeItemAtPath:VideoName error:nil];
}

assetExport.outputFileType = AVFileTypeQuickTimeMovie;
assetExport.outputURL = exportUrl;
assetExport.shouldOptimizeForNetworkUse = YES;

 //[strRecordedFilename setString: exportPath];

[assetExport exportAsynchronouslyWithCompletionHandler:
 ^(void ) {
     [assetExport release];
     dispatch_async(dispatch_get_main_queue(), ^{
         [self exportDidFinish:assetExport];
     });
 }
 ];

[videoAsset release];

}

 -(void)exportDidFinish:(AVAssetExportSession*)session
{
    NSURL *exportUrl = session.outputURL;
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:exportUrl])
    {
        [library writeVideoAtPathToSavedPhotosAlbum:exportUrl completionBlock:^(NSURL *assetURL, NSError *error)
        {
            dispatch_async(dispatch_get_main_queue(), ^{
                if (error) {
                    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Video Saving Failed"
                                                                   delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                    [alert show];
                } else {
                    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Video Saved" message:@"Saved To Photo Album"
                                                                   delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                    [alert show];
                }
            });
        }];

    }
    NSLog(@"Completed");
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"AlertView" message:@"Video is edited successfully." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];

}