Received memory warning when capturing screen and save to video ios

Question

I am now writing a program to capture screen and convert to video. I can successfully save the video if it is less than 10 seconds. But, if more than that, I received memory warning and application crash. I wrote this code as follow. Where am I missing to release data ? I would like to know how to do.

-(void)captureAndSaveImage
{

if(!stopCapturing){

if (assetWriterInput.readyForMoreMediaData)
{
    keepTrackOfBackGroundMood++;
    NSLog(@"keepTrackOfBackGroundMood is %d",keepTrackOfBackGroundMood);

    CVReturn cvErr = kCVReturnSuccess;

    CGSize imageSize = screenCaptureAndDraw.bounds.size;


    CGFloat imageScale = 0; //if zero, it reduce processing time

    if (NULL != UIGraphicsBeginImageContextWithOptions)
    {
        UIGraphicsBeginImageContextWithOptions(imageSize, NO, imageScale);
    }
    else
    {
        UIGraphicsBeginImageContext(imageSize);
    }

    [self.hiddenView.layer renderInContext:UIGraphicsGetCurrentContext()];

    [self.screenCaptureAndDraw.layer renderInContext:UIGraphicsGetCurrentContext()];


    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();



     image = (CGImageRef) [img CGImage];

    CVPixelBufferRef pixelBuffer = NULL;
    CFDataRef imageData= CGDataProviderCopyData(CGImageGetDataProvider(image));
    cvErr = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
                                         FRAME_WIDTH2,
                                         FRAME_HEIGHT2,
                                         kCVPixelFormatType_32BGRA,
                                         (void*)CFDataGetBytePtr(imageData),
                                         CGImageGetBytesPerRow(image),
                                         NULL,
                                         NULL,
                                         NULL,
                                         &pixelBuffer);


    //CFRelease(imageData);
    //CGImageRelease(image);  //I can't write this code because I am not creating it and when I check online, it say it is not my responsibility to release. If I write, the application crash immediately


    // calculate the time
    CFAbsoluteTime thisFrameWallClockTime = CFAbsoluteTimeGetCurrent();
    CFTimeInterval elapsedTime = thisFrameWallClockTime - firstFrameWallClockTime;


    // write the sample

    BOOL appended = [assetWriterPixelBufferAdaptor appendPixelBuffer:pixelBuffer withPresentationTime:presentationTime];

    if (appended) {
        NSLog (@"appended sample at time %lf and keepTrackofappended is %d", CMTimeGetSeconds(presentationTime),keepTrackofappended);
        keepTrackofappended++;
    } else {
        NSLog (@"failed to append");
        [self stopRecording];
        //self.startStopButton.selected = NO;
        screenRecord=false;
    }



}

}//stop capturing
// });


}

Answer 1

I agree that you don't want to do the CGImageRelease(image). This object was created by calling CGImage method of a UIImage object. Thus ownership was not transferred and ARC still does the memory management for your img object and no releasing of the image object is needed.

But I think you do want to restore your CFRelease(imageData). This is an object created by CGDataProviderCopyData, so you own it and must clean up.

I also think you have to release the pixelBuffer that you created with CVPixelBufferCreateWithBytes after you appendPixelBuffer. You can use the CVPixelBufferRelease function for that.

The Core Foundation memory rule is that if the function has Copy or Create in the name, you own that object and are responsible for releasing it. See the Create Rule in the Memory Management Programming Guide for Core Foundation.

I would have thought that the static analyzer (shift+command+B or "Analyze" from the Xcode "Product" menu) would have identified this issue, as it has gotten much better at finding Core Foundation memory issues (albeit, not perfect).

Alternatively, if you run your app through the Leaks tool in Instruments (which will also show you the Allocations tool at the same time), you can take a look at your memory usage. While the video capture requires a lot of Live Bytes, in my experience it stays pretty darn flat. If it's growing, you have a leak somewhere.