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IOS AVFoundation - Convert video to images at 60 frames per second

I am trying to convert an entire video into a sequence of images at 60 frames per second, which means 60 images generated per second video ...

For this, I use AVAssetImageGenerator and the generateCGImagesAsynchronouslyForTimes method ...

Everything is going well, except that I am having serious performance problems that regulate the execution time of batch processing (approximately 5 minutes per video in 13 seconds) ...

Also, above the next CGSizeMake size (512, 324), I am experiencing crashes ...

Does anyone already have experience with similar processing, and he knows how to reduce the execution time, as well as the ability to extract higher resolution images?

Below is the code I'm testing ...

NSURL *movieURL = [NSURL fileURLWithPath:getCaptureMoviePath()];

AVURLAsset *asset=[[AVURLAsset alloc] initWithURL:movieURL options:nil];
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc]  initWithAsset:asset];
generator.appliesPreferredTrackTransform=TRUE;
generator.requestedTimeToleranceAfter=kCMTimeZero;
generator.requestedTimeToleranceBefore=kCMTimeZero;
NSMutableArray *thumbTimes=[NSMutableArray arrayWithCapacity:asset.duration.value];

for(int t=0;t < asset.duration.value;t=t+2) {
    CMTime thumbTime = CMTimeMake(t, asset.duration.timescale);
    NSLog(@"Time Scale : %d ", asset.duration.timescale);
    NSValue *v=[NSValue valueWithCMTime:thumbTime];
        [thumbTimes addObject:v];
}
NSLog(@"thumbTimes array contains %d objects : ", [thumbTimes count]);
[asset release];
AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error) {
    if (result != AVAssetImageGeneratorSucceeded) {
        NSLog(@"couldn't generate thumbnail, error:%@", error);
    } else {
        NSLog(@"actual time: %lld/%d (requested: %lld/%d)",actualTime.value,actualTime.timescale,requestedTime.value,requestedTime.timescale);
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateFormat:@"yyyyMMdd-HHmmss"];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString *filename = [NSString stringWithFormat:@"%@.png", [formatter stringFromDate:[NSDate date]]];
        NSString *filepath = [documentsDirectory stringByAppendingPathComponent:filename];
        CFURLRef url = (CFURLRef)[NSURL fileURLWithPath:filepath];
        CGImageDestinationRef destination = CGImageDestinationCreateWithURL(url, kUTTypePNG, 1, NULL);
        CGImageDestinationAddImage(destination, im, nil);
        if (!CGImageDestinationFinalize(destination)) {     
            NSLog(@"Failed to write image to %@", filepath);
        }
        CFRelease(destination);
    }
    //[generator release];
};
CGSize maxSize = CGSizeMake(512, 324);
generator.maximumSize = maxSize;

[generator generateCGImagesAsynchronouslyForTimes:thumbTimes completionHandler:handler];

Thank you in advance

to.

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Hey @ Surya Joel will try to use the following code. It works great for me.

- (void)generateCMTimesArrayOfAllFramesUsingAsset:(AVURLAsset *)asset
{
    if (cmTimeArray.count>0) {
        [cmTimeArray removeAllObjects];
    }
    //Generate all frames present in video
    for(int t=0;t < asset.duration.value;t++) {
        CMTime thumbTime = CMTimeMake(t,asset.duration.timescale);
        NSValue *v=[NSValue valueWithCMTime:thumbTime];
        [cmTimeArray addObject:v];
    }
    NSLog(@"Array of time %@ count = %d",cmTimeArray, cmTimeArray.count);
    //NSLog(@"Array count = %d",cmTimeArray.count);
}


- (void)generateCMTimesArrayOfFrames:(int)framesInterval UsingAsset:(AVURLAsset *)asset
{
    int videoDuration = ceilf(((float)asset.duration.value/asset.duration.timescale));
    NSLog(@"Video duration %lld seconds timescale = %d",asset.duration.value,asset.duration.timescale);
    if (cmTimeArray.count>0) {
        [cmTimeArray removeAllObjects];
    }
    //Generate limited frames present in video
    for (int i = 0; i<videoDuration; i++)
   {
       int64_t tempInt = i;
       CMTime tempCMTime = CMTimeMake(tempInt,1);
       int32_t interval = framesInterval;
       for (int j = 1; j<framesInterval+1; j++)
       {
            CMTime newCMtime = CMTimeMake(j,interval);
            CMTime addition = CMTimeAdd(tempCMTime, newCMtime);
            [cmTimeArray addObject:[NSValue valueWithCMTime:addition]];
       }
   }
   NSLog(@"Array of time %@ count = %d",cmTimeArray, cmTimeArray.count);
   //NSLog(@"Array count = %d",cmTimeArray.count);
}


- (void)generateThumbnailsFromVideoURL:(AVURLAsset *)videoAsset
{
    //Generate CMTimes Array of required frames
    //1.Generate All Frames
    //[self generateCMTimesArrayOfAllFramesUsingAsset:asset];

    //2.Generate specific frames per second
    [self generateCMTimesArrayOfFrames:30 UsingAsset:videoAsset];

    __block int i = 0;
    AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error){
    if (result == AVAssetImageGeneratorSucceeded) {
        [framesArray addObject:[UIImage imageWithCGImage:im]];
    }
    if (result == AVAssetImageGeneratorFailed) {
        NSLog(@"Failed with error: %@ code %d", [error localizedDescription],error.code);
    }
    if (result == AVAssetImageGeneratorCancelled) {
        NSLog(@"Canceled");
    }

    i++;
    imageIndex = i;

    if(i == cmTimeArray.count) {
        //Thumbnail generation completed
    }
};

    // Launching the process...
    self.generator = [[AVAssetImageGenerator alloc] initWithAsset:videoAsset];
    self.generator.apertureMode = AVAssetImageGeneratorApertureModeCleanAperture;
    self.generator.appliesPreferredTrackTransform=TRUE;
    self.generator.requestedTimeToleranceBefore = kCMTimeZero;
    self.generator.requestedTimeToleranceAfter = kCMTimeZero;
    self.generator.maximumSize = CGSizeMake(40, 40);
    [self.generator generateCGImagesAsynchronouslyForTimes:cmTimeArray completionHandler:handler];
}
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