CGContextDrawImage huge memory peak - ios

Question

I'm developing a movie maker application which make some effects on imported videos.
I'm using AVAssetWriter to code my application.
Everything works very good but I have a big problem in memory.
My app takes over 500 MB of the RAM in buffering process.
Simply the algorithm for making a filtered video is going like this:
1- import video.
2- extract all the frames for the video as CMSampleBuffer objects.
3- convert CMSampleBuffer object to uiimage.
4- implement the filter on the uiimage.
5- convert the uiimage back to a new CMSAmpleBuffer object.
6- Append the new buffer to a writer output.
7- Finally save the new movie to PhotoGallery.
The problem is in step5 I have a function which converts a UIImage to cvpixelBuffer object and return it.
Then I convert the CVPixelBuffer object to CMSampleBuffer.
The function increases the memory a lot and the application crashes at the end.
This is my code:
-(CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image andSize:(CGSize)size
{
double height = CGImageGetHeight(image);
double width = CGImageGetWidth(image);
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
[NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
nil];
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width,
size.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
&pxbuffer);
if (status != kCVReturnSuccess) {
return NULL;
}
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata,size.width ,
size.height, 8, 4*size.width, rgbColorSpace,
kCGImageAlphaNoneSkipFirst);
CGFloat Y ;
if (height == size.height)
Y = 0;
else
Y = (size.height /2) - (height/2) ;
CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
CGContextDrawImage(context, CGRectMake(0, Y,width,height), image);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
return pxbuffer;
}
CGContextDrawImage increases the memory by 2~5 MB per frame conversion.
I tried the following solutions:
1- releasing pxbuffer using CFRelease.
2- I used CGImageRelease to release the image ref.
3- I surrounded the code with #autoreleasepool block.
4- I used CGContextRelease.
5- UIGraphicsEndImageContext.
6- Used Analyze too in Xcode and fixed all the points.
Here is the full code for Video filtering:
- (void)assetFilteringMethod:(FilterType)filterType AndAssetURL:(NSURL *)assetURL{
CMSampleBufferRef sbuff ;
[areader addOutput:rout];
[areader startReading];
UIImage* bufferedImage;
while ([areader status] != AVAssetReaderStatusCompleted) {
sbuff = [rout copyNextSampleBuffer];
if (sbuff == nil)
[areader cancelReading];
else{
if (writerInput.readyForMoreMediaData) {
#autoreleasepool {
bufferedImage = [self imageFromSampleBuffer:sbuff];
bufferedImage = [FrameFilterClass convertImageToFilterWithFilterType:filterType andImage: bufferedImage];
CVPixelBufferRef buffer = NULL;
buffer = [self pixelBufferFromCGImage:[bufferedImage CGImage] andSize:CGSizeMake(320,240)];
[adaptor appendPixelBuffer:buffer withPresentationTime:CMSampleBufferGetPresentationTimeStamp(sbuff)];
CFRelease(buffer);
CFRelease(sbuff);
}
}
}
}
//Finished buffering
[videoWriter finishWritingWithCompletionHandler:^{
if (videoWriter.status != AVAssetWriterStatusFailed && videoWriter.status == AVAssetWriterStatusCompleted){
dispatch_async(dispatch_get_main_queue(), ^{
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
if ([library
videoAtPathIsCompatibleWithSavedPhotosAlbum:[NSURL fileURLWithPath:moviePath]]) {
[library writeVideoAtPathToSavedPhotosAlbum:[NSURL fileURLWithPath:moviePath]
completionBlock:^(NSURL *assetURL, NSError *error){
}];
}
});
}
else
NSLog(#"Video writing failed: %#", videoWriter.error);
}];
}
I spent around 3 to 4 days trying to solve this problem...
Any help would be appreciated.

Answer 1

You have to release the image using this line:
cgimagerelease(image.cgimage)