iPhone Read Uiimage (Frames) from Video with Avfoundation

iPhone Read UIimage (frames) from video with AVFoundation

You're talking about using the calls for generating what Apple calls thumbnail images from videos at specific times.

For an MPMoviePlayerController (what iOS uses to hold a video from a file or other source), there are two commands to do this. The first one generates a single thumbnail (image) from a movie at a specific point in time, and the second one generates a set of thumbnails for a time range.

This example gets an image at 10 seconds into a movie clip, myMovie.mp4:

MPMoviePlayerController *movie = [[MPMoviePlayerController alloc]
        initWithContentURL:[NSURL URLWithString:@"myMovie.mp4"]];
UIImage *singleFrameImage = [movie thumbnailImageAtTime:10 
        timeOption:MPMovieTimeOptionExact];

Note that this performs synchronously - i.e. the user will be forced to wait while you get the screenshot.

The other option is to get a series of images from a movie, from an array of times:

MPMoviePlayerController *movie = [[MPMoviePlayerController alloc]
        initWithContentURL [NSURL URLWithString:@"myMovie.mp4"]];
NSNumber time1 = 10;
NSNumber time2 = 11;
NSNumber time3 = 12;
NSArray *times = [NSArray arrayWithObjects:time1,time2,time3,nil];
[movie requestThumbnailImagesAtTimes:times timeOption:MPMovieTimeOptionExact];

This second way will trigger a notification of type MPMoviePlayerThumbnailImageRequestDidFinishNotification each time a new image is generated. You can set up an observer to monitor this and process the image - I'll leave you to work that bit out on your own!

iOS extracting video frames as images

I think the answer in this question is what you are looking for.

iPhone Read UIimage (frames) from video with AVFoundation.

There are 2 methods specified by the accepted answer. You can use either one according to your requirement.

Reading video frame-by-frame under iOS

The two links above actually answer my question and the empty copyNextBufferSample is an issue with iOS SDK 5.0b3, it works on the device.

When reading frames from a video on an iPad with AVAssetReader, the images are not properly oriented

After some exploration, I came across the following that allowed me to obtain the video's orientation from the AVAssetTrack:

let transform = assetTrack.preferredTransform
radians = atan2(transform.b, transform.a)

Once I had that, I was able to convert it to degrees:

let degrees = (radians * 180.0) / .pi

Then, using a switch statement I could determine how to rotate the image:

Switch Int(degrees) {
   case -90, 90:
       // Rotate accordingly
   case 180:
       // Flip
   default:
       // Do nothing
}

Output from AVAssetWriter (UIImages written to video) distorted

Ok, this turned out to be an issue with the aspect ratio of the images I was reading in being different from the aspect ratio of the PixelBuffer I was creating. Made them equal and it works fine.

Grab frames from video using Swift

Thanks to @eric-d who found this post:
iOS Take Multiple Screen Shots

I manage to find out that adding:

    assetImgGenerate.requestedTimeToleranceAfter = kCMTimeZero;
    assetImgGenerate.requestedTimeToleranceBefore = kCMTimeZero;

...to my function will do the trick.

My updated function looks like this:

func generateThumnail(url : NSURL, fromTime:Float64) -> UIImage {
    var asset :AVAsset = AVAsset.assetWithURL(url) as! AVAsset
    var assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    assetImgGenerate.requestedTimeToleranceAfter = kCMTimeZero;
    assetImgGenerate.requestedTimeToleranceBefore = kCMTimeZero;
    var error       : NSError? = nil
    var time        : CMTime = CMTimeMakeWithSeconds(fromTime, 600)        
    var img         : CGImageRef = assetImgGenerate.copyCGImageAtTime(time, actualTime: nil, error: &error)
    var frameImg    : UIImage = UIImage(CGImage: img)!
    return frameImg
}

var grabTime = 1.22
img = generateThumnail(urlVideo, fromTime: Float64(grabTime))

How to extract images from a video?

Simple way to extract thumbnails from a movie is to use MPMoviePlayerController class and its - thumbnailImageAtTime:timeOption: method.

For example you've got a filepath url:

NSURL *tempFilePathURL = ...;
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL: tempFilePathURL];
UIImage *thumbnail = [player thumbnailImageAtTime:THUMBNAIL_TIME timeOption:MPMovieTimeOptionExact];
[player release];

I used it in my code and it worked.

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