ios - AVFoundation:copyCGImageAtTime 总是返回 nil

Question

我正在尝试从视频中获取所有帧，但它总是在

cgImage = try assetImgGenerate.copyCGImageAtTime(time, actualTime: nil)

我当前的代码是这样的

if let path = NSBundle.mainBundle().resourcePath {
        let fullPath = path + "/mov/watch_phone.mov"
        let url = NSURL(fileURLWithPath: fullPath)
        mutableVideoURL = url
        getFrame()
        print(videoFrames.count)
    }

func getFrame() {
    let asset:AVAsset = AVAsset(URL:self.mutableVideoURL as NSURL)
    let assetImgGenerate:AVAssetImageGenerator = AVAssetImageGenerator(asset:asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    let duration:Float64 = CMTimeGetSeconds(asset.duration)
    let durationInt:Int = Int(duration)

    for index:Int in 0 ..< durationInt
    {
        generateFrames(assetImgGenerate, fromTime: Float64(index))
    }
}

func generateFrames(assetImgGenerate:AVAssetImageGenerator, fromTime:Float64)
{
    let time:CMTime = CMTimeMakeWithSeconds(fromTime, 600)
    let cgImage:CGImage?

    do
    {
        cgImage = try assetImgGenerate.copyCGImageAtTime(time, actualTime: nil)
        let frameImg:UIImage = UIImage(CGImage:cgImage!)
        videoFrames.append(frameImg)
    }
    catch let error as NSError {

        print("Found error in saving entity changes \(error)")
    }

copyCGImageAtTime 总是返回 nil。该视频已添加到我的 bundle 中，并且还出现在构建阶段的捆绑资源中。

这是在 catch block 中收到的错误

Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSUnderlyingError=0x1700563e0 {Error Domain=NSOSStatusErrorDomain Code=-12430 "(null)"}, NSLocalizedFailureReason=An unknown error occurred (-12430), NSLocalizedDescription=The operation could not be completed}

请帮助我理解我在这里做错了什么

Answer 1

这是一个工作代码。试试这个，确保你有非零 Assets ，正确的时间。

- (UIImage *)getUIImageOfVideoAsset:(AVAsset *)asset atTime:(CMTime)time withSize:(CGSize)size {

NSError *error;
AVAssetImageGenerator *baseImageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
baseImageGenerator.appliesPreferredTrackTransform = YES;
baseImageGenerator.maximumSize = size;

CGImageRef cgImage = [baseImageGenerator copyCGImageAtTime:time actualTime:NULL error:&error];
UIImage *image = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);

return image;
}