Create CVPixelBufferRef from CIImage for Writing to File

Question

I'm writing a custom Movie Recording app and have implemented AVAssetWriter and AVAssetWriterInputPixelBufferAdaptor for writing frames to a file. In the DataOutputDelegate callback I am trying to apply a CIFilter to the sampleBuffer. First I get a CVPixelBufferRef and then create a CIImage. I then apply the CIIFilter and grab the resulting CIImage:

    CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);

    CIImage *image = [CIImage imageWithCVPixelBuffer:pixelBuffer];
    CIFilter *hueAdjust = [CIFilter filterWithName:@"CIHueAdjust"];
    [hueAdjust setDefaults];
    [hueAdjust setValue: image forKey: @"inputImage"];
    [hueAdjust setValue: [NSNumber numberWithFloat: 2.094]
                 forKey: @"inputAngle"];

    CIImage *result = [hueAdjust valueForKey: @"outputImage"];

    CVPixelBufferRef newBuffer = //Convert CIImage...

How would I go about converting that CIImage so I can:

    [self.filteredImageWriter appendPixelBuffer:newBuffer withPresentationTime:lastSampleTime];

Answer 1

UPDATED ANSWER

While my previous method works, I was able to tweak it to simplify the code. It also seems to runs slightly faster.

samplePixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(samplePixelBuffer, 0); // NOT SURE IF NEEDED // NO PERFORMANCE IMPROVEMENTS IF REMOVED

NSDictionary *options = [NSDictionary dictionaryWithObject:(__bridge id)rgbColorSpace forKey:kCIImageColorSpace];                
outputImage = [CIImage imageWithCVPixelBuffer:samplePixelBuffer options:options];

//-----------------
// FILTER OUTPUT IMAGE

@autoreleasepool {

    outputImage = [self applyEffectToCIImage:outputImage dict:dict];

}
CVPixelBufferUnlockBaseAddress(samplePixelBuffer, 0); // NOT SURE IF NEEDED // NO PERFORMANCE IMPROVEMENTS IF REMOVED

//-----------------
// RENDER OUTPUT IMAGE BACK TO PIXEL BUFFER

[self.filterContext render:outputImage toCVPixelBuffer:samplePixelBuffer bounds:[outputImage extent] colorSpace:CGColorSpaceCreateDeviceRGB()]; // DOES NOT SEEM TO WORK USING rgbColorSpace

PREVIOUS ANSWER

I just implemented the following to get the pixel buffer from a CIImage. Make sure your pixel formats are consistent otherwise you will have color issues. Also the CFDictionaries are very important. http://allmybrain.com/2011/12/08/rendering-to-a-texture-with-ios-5-texture-cache-api/

CFDictionaryRef empty = CFDictionaryCreate(kCFAllocatorDefault, // EMPTY IOSURFACE DICT
                                           NULL,
                                           NULL,
                                           0,
                                           &kCFTypeDictionaryKeyCallBacks,
                                           &kCFTypeDictionaryValueCallBacks);
CFMutableDictionaryRef attributes = CFDictionaryCreateMutable(kCFAllocatorDefault,
                                                         1,
                                                         &kCFTypeDictionaryKeyCallBacks,
                                                         &kCFTypeDictionaryValueCallBacks);

CFDictionarySetValue(attributes,kCVPixelBufferIOSurfacePropertiesKey,empty);

CVPixelBufferRef pixelBuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, 
                                      outputImage.extent.size.width, 
                                      outputImage.extent.size.height, 
                                      kCVPixelFormatType_32BGRA, 
                                      attributes, 
                                      &pixelBuffer);

if (status == kCVReturnSuccess && pixelBuffer != NULL) {

    CVPixelBufferLockBaseAddress(pixelBuffer, 0); // NOT SURE IF NEEDED // KEPT JUST IN CASE
    [self.filterContext render:outputImage toCVPixelBuffer:pixelBuffer bounds:[outputImage extent] colorSpace:CGColorSpaceCreateDeviceRGB()];
    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0); // NOT SURE IF NEEDED // KEPT JUST IN CASE

}