Question

I am using AVFoundation framework in my iPad app to record videos.When recording of a video is completed, I create a thumbnail image for same video using AVFoundation.But if I record two videos without much time delay in between then thumbnail is not created properly.Clearly it’s taking some delay.How to avoid that or at least how can I know when the thumbnail of previous video has got created completely so that I can show some ‘Wait’ symbol to the user for that time period?

Please help as I am having no clue to resolve the issue.

//delegate method which gets called when recording ends.
//Here I create the thumb and store it in self.thumb
-(void)recorder:(AVCamRecorder *)recorder recordingDidFinishToOutputFileURL:(NSURL *)outputFileURL error:(NSError *)error
{
    self.thumb=nil;
    AVURLAsset *asset=[[AVURLAsset alloc] initWithURL:outputFileURL options:nil];
    AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
    generator.appliesPreferredTrackTransform=TRUE;
    [asset release];
    CMTime thumbTime = CMTimeMakeWithSeconds(0,1);

    AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error){
        if (result != AVAssetImageGeneratorSucceeded) {
            NSLog(@"couldn't generate thumbnail, error:%@", error);
        }

         self.thumb=[UIImage imageWithCGImage:im];

        [generator release];
    };

    CGSize maxSize = CGSizeMake(320, 180);
    generator.maximumSize = maxSize;
    [generator generateCGImagesAsynchronouslyForTimes:[NSArray arrayWithObject:[NSValue valueWithCMTime:thumbTime]] completionHandler:handler];

    if ([[UIDevice currentDevice] isMultitaskingSupported]) {
        [[UIApplication sharedApplication] endBackgroundTask:[self backgroundRecordingID]];
    }       

    if ([[self delegate] respondsToSelector:@selector(captureManagerRecordingFinished:)]) {
        [[self delegate] captureManagerRecordingFinished:self];
    }
}


[self copyFileToDocuments:outputFileURL];
}


//Save video and thumbnail to documents
- (void) copyFileToDocuments:(NSURL *)fileURL
{
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd_HH-mm-ss"];
NSString *destinationPath = [documentsDirectory stringByAppendingFormat:@"/output_%@.mov", [dateFormatter stringFromDate:[NSDate date]]];
[dateFormatter release];
NSError *error;
if (![[NSFileManager defaultManager] copyItemAtURL:fileURL toURL:[NSURL fileURLWithPath:destinationPath] error:&error]) {
    if ([[self delegate] respondsToSelector:@selector(captureManager:didFailWithError:)]) {
        [[self delegate] captureManager:self didFailWithError:error];
    }
}
else
{
    destinationPath=[[destinationPath lastPathComponent]stringByDeletingPathExtension];
    [self saveImage:self.thumb withName:destinationPath];
}

}

    //Method Where I save  self.thumb in app documents
-(void) saveImage:(UIImage*)image withName:(NSString*)fileName
{
NSFileManager *fileManager = [NSFileManager defaultManager];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];
   //Save Image
NSData *imageData = UIImagePNGRepresentation(image); //convert image into .png format.

NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",fileName]];

[fileManager createFileAtPath:fullPath contents:imageData attributes:nil];

}

Above is my code.
But self.thumb is not getting properly saved if I don’t give delay in two recordings.

Answer 1

I used a different method.When user clicks ‘Record’ I first click a photo from camera and then start recording the video.Later I use the same photo as a thumbnail.

I know this is not the best approach but the best thing is its working 😉

Hope this helps someone with the same problem.