Receive memory warning when I create video from images

Question

I was working with create video from images and its working very well but undortunatelly application getting crash in iPhone 4s. see my code and provide your suggestion please.

- (void)createMovieFromImages:(NSArray *)images withCompletion:(CEMovieMakerCompletion)completion;
{
    self.completionBlock = completion;

    [self.assetWriter startWriting];
    [self.assetWriter startSessionAtSourceTime:kCMTimeZero];

    dispatch_queue_t mediaInputQueue = dispatch_queue_create("mediaInputQueue", NULL);

    __block NSInteger i = 0;

    NSInteger frameNumber = [images count];

    [self.writerInput requestMediaDataWhenReadyOnQueue:mediaInputQueue usingBlock:^{
        while (YES){
            if (i >= frameNumber) {
                break;
            }
            if ([self.writerInput isReadyForMoreMediaData]) {

                CVPixelBufferRef sampleBuffer = [self newPixelBufferFromCGImage:[[images objectAtIndex:i] CGImage]];

                if (sampleBuffer) {
                    if (i == 0) {
                        [self.bufferAdapter appendPixelBuffer:sampleBuffer withPresentationTime:kCMTimeZero];
                    }else{
                        CMTime lastTime = CMTimeMake(i-1, self.frameTime.timescale);
                        CMTime presentTime = CMTimeAdd(lastTime, self.frameTime);
                        [self.bufferAdapter appendPixelBuffer:sampleBuffer withPresentationTime:presentTime];
                    }
                    CFRelease(sampleBuffer);
                    i++;
                }
            }
        }

        [self.writerInput markAsFinished];
        [self.assetWriter finishWritingWithCompletionHandler:^{
            dispatch_async(dispatch_get_main_queue(), ^{
                self.completionBlock(self.fileURL);
            });
        }];

        CVPixelBufferPoolRelease(self.bufferAdapter.pixelBufferPool);
    }];
}


- (CVPixelBufferRef)newPixelBufferFromCGImage:(CGImageRef)image
{
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
                             nil];

    CVPixelBufferRef pxbuffer = NULL;

    CGFloat frameWidth = [[self.videoSettings objectForKey:AVVideoWidthKey] floatValue];
    CGFloat frameHeight = [[self.videoSettings objectForKey:AVVideoHeightKey] floatValue];


    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault,
                                          frameWidth,
                                          frameHeight,
                                          kCVPixelFormatType_32ARGB,
                                          (__bridge CFDictionaryRef) options,
                                          &pxbuffer);

    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
    NSParameterAssert(pxdata != NULL);

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context = CGBitmapContextCreate(pxdata,
                                                 frameWidth,
                                                 frameHeight,
                                                 8,
                                                 4 * frameWidth,
                                                 rgbColorSpace,
                                                 (CGBitmapInfo)kCGImageAlphaNoneSkipFirst);
    NSParameterAssert(context);
    CGContextConcatCTM(context, CGAffineTransformIdentity);
    CGContextDrawImage(context, CGRectMake(0,
                                           0,
                                           CGImageGetWidth(image),
                                           CGImageGetHeight(image)),
                       image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}

I have pass image array and get video but it was crash in iPhone 4s please help me.

Answer 1

This issue is becoming more common because of some of the following:

1. "iPhone 4S has 512 MB of DDR2 RAM" (wiki) , and with the numerous processes of the OS and their own demands of the hardware, and the addition of age of the device (wear and tear), an iPhone 4s is unlikely to be capable of something as demanding as this.
2. This question (ios app maximum memory budget) assumes that no more than 200MB (to be safe keep around 120MB) of memory should be consumed by the app at any given time.

To try and make this work, place as many functions not relevant to User Interface on background threads. Your entire - (CVPixelBufferRef)newPixelBufferFromCGImage:(CGImageRef)image is handled on the main thread, as your method - (void)createMovieFromImages:(NSArray *)images...

There is no guarantee placing these methods on a background thread will work, but it is worth trying. The following questions/answer/links have some relevant points of interest regarding threading, if you are not aware of them, and even if you are some of the points are interesting to read as a developer:

1. GCD - main vs background thread for updating a UIImageView
2. NSOperation and NSOperationQueue working thread vs main thread
3. http://pinkstone.co.uk/how-to-execute-a-method-on-a-background-thread-in-ios/