我无法从1.8秒的视频中获得用于生成静止图像的精确CMTime [英] I cannot get a precise CMTime for Generating Still Image from 1.8 second Video

问题描述

每次我尝试从视频资产生成静止帧时，都会在0.000 ..秒的时间生成该静止帧.我可以从我的日志消息中看到这一点.好消息是，我可以在0.000 ..的时间获取图像，以显示在名为"myImageView"的UIImageView中.我以为问题是未设置AVURLAssetPreferPreciseDurationAndTimingKey，但是即使在我知道如何做到这一点之后，它仍然无法正常工作.

Every time I try to generate a still frame from my video asset, it is generated at a time of 0.000.. seconds. I can see this from my log message. The good thing is that I can get the image at time 0.000.. to show up in a UIImageView called "myImageView." I thought the problem was that AVURLAssetPreferPreciseDurationAndTimingKey was not set, but even after I figured out how to do that, it still does not function..

这就是我所拥有的..

Here is what I have..

时间，实际时间和生成在标头中声明

time, actualTime, and generate are declared in the Header

NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/videoTest4.m4v"]];
//UISaveVideoAtPathToSavedPhotosAlbum(path, self, @selector(video:didFinishSavingWithError:contextInfo:), nil);
NSURL *url = [NSURL fileURLWithPath:path];

NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:url options:options];

Float64 durationSeconds = CMTimeGetSeconds([asset duration]);

generate = [[AVAssetImageGenerator alloc] initWithAsset:asset];
NSError *err = nil;

time = CMTimeMake(600,600.0);
CGImageRef imgRef = [generate copyCGImageAtTime:time actualTime:&actualTime error:&err];
UIImage *currentImg = [[UIImage alloc] initWithCGImage:imgRef];
myImageView.image = currentImg;

NSLog(@"The total Video Duration is %f",durationSeconds);
NSLog(@"The time I want my image is %f",CMTimeGetSeconds(time));
NSLog(@"The actual time my image was take was %f",CMTimeGetSeconds(actualTime));

然后我的控制台显示.

2011-04-28 18:49:59.062 videoTest [26553:207]总视频时长为1.880000

2011-04-28 18:49:59.062 videoTest[26553:207] The total Video Duration is 1.880000

2011-04-28 18:49:59.064 videoTest [26553:207]我想要我的图像的时间是1.000000

2011-04-28 18:49:59.064 videoTest[26553:207] The time I want my image is 1.000000

2011-04-28 18:49:59.064 videoTest [26553:207]我的图像实际拍摄时间为0.000000

2011-04-28 18:49:59.064 videoTest[26553:207] The actual time my image was take was 0.000000

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非常感谢你们..:)

推荐答案

要解决此问题，您只需将 requestedTimeToleranceBefore 和 requestedTimeToleranceAfter 设置为kCMTimeZero，以用于AVAssetImageGenerator.

To resolve this you just need to set requestedTimeToleranceBefore and requestedTimeToleranceAfter to kCMTimeZero for AVAssetImageGenerator.

AVAssetImageGenerator类参考

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