使用AVFoundation的视频的第一帧

Question

I'm trying to get the first frame of a video using the classes in AVFoundation. But it appears to not be getting an image at all.

My code currently looks like this

AVURLAsset* asset = [AVURLAsset URLAssetWithURL:[NSURL URLWithString:videoPath] options:nil];
AVAssetImageGenerator* imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
UIImage* image = [UIImage imageWithCGImage:[imageGenerator copyCGImageAtTime:CMTimeMake(0, 1) actualTime:nil error:nil]];
[videoFrame setImage:image];

The value of video path is /var/mobile/Applications/02F42CBF-D8BD-4155-85F2-8CF1E55B5023/Documents/videos/1334300431637030.mp4 which is definitely a video, since I can play it with MPMoviePlayerViewController . I'm not sure what I'm doing wrong but any suggestions would be helpful.

Thanks.

Answer 1

I solved it. Apparently using [NSURL fileURLWithPath:videoPath] instead of [NSURL URLWithString:videoPath] makes all the difference.

Answer 2

I used null0pointer solution but in some videos I recieved the first frame rotated. To resolve this issue I set to TRUE the appliesPreferredTrackTransform property of AVAssetImageGenerator. And this code looks like this:

AVURLAsset* asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
AVAssetImageGenerator* imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
[imageGenerator setAppliesPreferredTrackTransform:TRUE];
UIImage* image = [UIImage imageWithCGImage:[imageGenerator copyCGImageAtTime:CMTimeMake(0, 1) actualTime:nil error:nil]];
[self.imageView setImage:image];

Answer 3

Doing this in Swift 4.0 :

            // Assumes you have a local `fileURL`

            var avAsset = AVURLAsset(url: fileURL, options: nil)
            var imageGenerator = AVAssetImageGenerator(asset: avAsset)
            imageGenerator.appliesPreferredTrackTransform = true
            var thumbnail: UIImage?

            do {
                thumbnail = try UIImage(cgImage: imageGenerator.copyCGImage(at: CMTime(seconds: 0, preferredTimescale: 1), actualTime: nil))
            } catch let e as NSError {
                print("Error: \(e.localizedDescription)")
            }