具有无AVAsset的纯色的AVMutableComposition [英] AVMutableComposition of a Solid Color with No AVAsset
问题描述
这是我的最终目标:我想使用 AVVideoCompositionCoreAnimationTool
从Core Animation创建视频。 我不会在此合成中使用现有的AVAsset。
Here's my end goal: I'd like to use AVVideoCompositionCoreAnimationTool
to create a video from Core Animation. I will not be using an existing AVAsset in this composition.
我的问题是,如何使用 AVMutableComposition
在给定的时间内制作一个静态纯色的视频吗?在我想出来之后,我可以添加动画。
My question is, how can I use AVMutableComposition
to make a video with a static solid color for a given amount of time? After I figure that out, I can add the animation.
这是我的代码:
- (void)exportVideo {
AVMutableComposition *mixComposition = [AVMutableComposition composition];
CMTimeRange timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(10, 600));
[mixComposition insertEmptyTimeRange:timeRange];
AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[videoTrack insertEmptyTimeRange:timeRange];
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
mainInstruction.timeRange = timeRange;
mainInstruction.backgroundColor = [UIColor blueColor].CGColor;
AVMutableVideoComposition *mainComposition = [AVMutableVideoComposition videoComposition];
mainComposition.renderSize = CGSizeMake(500, 500);
mainComposition.instructions = [NSArray arrayWithObject:mainInstruction];
mainComposition.frameDuration = CMTimeMake(1, 30);
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];
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL = url;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.videoComposition = mainComposition;
[exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
[self exportDidFinish:exporter];
});
}];
}
我知道你必须添加至少一首曲目到mixComposition,所以我添加了一个视频轨道并插入了一个空的时间范围,但是当我调用 exportAsynchronouslyWithCompletionHandler
时,从不调用处理程序。我可以在调用export后的任何时间内添加 dispatch_after
并观察导出器的状态为 AVAssetExportSessionStatusExporting
。
I know you have to add at least one track to the mixComposition, so I've added a video track and inserted an empty time range, but when I call exportAsynchronouslyWithCompletionHandler
, the handler is never called. I can add a dispatch_after
for any amount of time after I call export and observe that the exporter has a status of AVAssetExportSessionStatusExporting
.
我做错了什么?
推荐答案
玩完之后几个月前,我发现让它发挥作用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。
After playing around with this a few months ago I found that the only reliable way to get it to work is to use a short, blank video in your AVMutableCompositionTrack, then overlay it with the desired layers.
由于模拟器中的错误,我在一个月前将项目上传到GitHub。如果您愿意,可以下载空白视频此处。
I uploaded a project to GitHub about a month ago as a result of a bug in the simulator. You can download the blank video here, if you'd like.
-(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];
});
}];
}
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