Not able to Extract each and every frame from Video - objective-c

Question

I have a 7 second MOV video at 30fps, but when I try to loop the code for multiple values it doesn't work. It always give me 7-8 unique frames even if I am able to write all frames.
Requested times are always different but I always get actual time frames.
MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:#"video" ofType:#"MOV"]]];
moviePlayer.shouldAutoplay = NO;
NSMutableArray *timesm=[[NSMutableArray alloc]init];
for (int i=0; i<frames; i++) {
CMTime firstThird = CMTimeMakeWithSeconds(videoDurationSeconds *i/(float)frames, 600);
[timesm addObject:[NSValue valueWithCMTime:firstThird]];
double abc=firstThird.value/600;
UIImage *thumbnail = [moviePlayer thumbnailImageAtTime:abc timeOption:MPMovieTimeOptionExact];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:#"zshipra %i.jpg",i]];
NSData *imageData = UIImageJPEGRepresentation(thumbnail,0.7);
[imageData writeToFile:savedImagePath atomically:NO];
}
I also tried another way from the Apple developer site, but both are giving 7 frames from 7 seconds video.
AVAssetImageGenerator *generate1 = [[AVAssetImageGenerator alloc] initWithAsset:asset1];
generate1.appliesPreferredTrackTransform = YES;
NSError *err = NULL;
CMTime videoDuration = asset1.duration;
float videoDurationSeconds = CMTimeGetSeconds(videoDuration);
int frames=(int)videoDurationSeconds*30;
NSMutableArray *timesm=[[NSMutableArray alloc]init];
for (int i=0; i<frames; i++) {
CMTime firstThird = CMTimeMakeWithSeconds(videoDurationSeconds *i/(float)frames, 600);
[timesm addObject:[NSValue valueWithCMTime:firstThird]];
}
[generate1 generateCGImagesAsynchronouslyForTimes:timesm
completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error) {
UIImage* myImage = [[UIImage alloc] initWithCGImage:image];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:#"ankur-%# %i.jpg",image,(int)[[NSDate date] timeIntervalSince1970]]];
NSData *imageData = UIImageJPEGRepresentation(myImage,0.7);
[imageData writeToFile:savedImagePath atomically:NO];
NSString *requestedTimeString = (NSString *)
CFBridgingRelease(CMTimeCopyDescription(NULL, requestedTime));
NSString *actualTimeString = (NSString *)
CFBridgingRelease(CMTimeCopyDescription(NULL, actualTime));
NSLog(#"Requested: %#; actual %#", requestedTimeString, actualTimeString);
if (result == AVAssetImageGeneratorSucceeded) {
// Do something interesting with the image.
}
if (result == AVAssetImageGeneratorFailed) {
NSLog(#"Failed with error: %#", [error localizedDescription]);
}
if (result == AVAssetImageGeneratorCancelled) {
NSLog(#"Canceled");
}
}];

Answer 1

I've tested with your code. And with two changes, it seems all the frame images are successfully generated.
1) Specify the tolerance options
generate1.requestedTimeToleranceAfter = CMTimeMakeWithSeconds(1/30.0, videoDuration.timescale);
generate1.requestedTimeToleranceBefore = CMTimeMakeWithSeconds(1/30.0, videoDuration.timescale);
2) Use native CMTime unit, not second unit
NSMutableArray *timesm=[[NSMutableArray alloc]init];
for (int i=0; i<frames; i++) {
CMTime firstThird = CMTimeMake( i * (videoDuration.timescale / 30.0f), videoDuration.timescale);
[timesm addObject:[NSValue valueWithCMTime:firstThird]];
}