Create video from images with same size (height and width of all images in given cgsize) in iphone

Question

I want to create video from images taken from gallery. I have stored images into an array. Now I want to create video from it with size user gives. I have written code but it displays black area if image is small then given size. Can anyone kindly help me to solve this?

Any needful help will be appreciated.

Code I'm using to generate video :

-(void) writeImagesToMovieAtPath:(NSString *)path withSize:(CGSize) size
{    
    NSLog(@"Write Started");

    NSError *error = nil;

    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                                  [NSURL fileURLWithPath:path] fileType:AVFileTypeMPEG4
                                                              error:&error];
    NSParameterAssert(videoWriter);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt:size.height], AVVideoHeightKey,
                                   nil];


    AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
                                             assetWriterInputWithMediaType:AVMediaTypeVideo
                                             outputSettings:videoSettings];




    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                     assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput
                                                     sourcePixelBufferAttributes:nil];

    NSParameterAssert(videoWriterInput);

    NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
    videoWriterInput.expectsMediaDataInRealTime = YES;
    [videoWriter addInput:videoWriterInput];
    //Start a session:
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];


    //Video encoding

    CVPixelBufferRef buffer = NULL;

    //convert uiimage to CGImage.

    int frameCount = 0;

    for(int i = 0; i<[arrSelectedImgs count]; i++)
    {
       // UIImage *img = [self scaleImage:[arrSelectedImgs objectAtIndex:i] toSize:size];

        buffer = [self pixelBufferFromCGImage:[[arrSelectedImgs objectAtIndex:i] CGImage] size:size];

        BOOL append_ok = NO;
        int j = 0;
        while (!append_ok && j < 30)
        {
            if (adaptor.assetWriterInput.readyForMoreMediaData)
            {
                printf("appending %d attemp %d\n", frameCount, j);

                CMTime frameTime = CMTimeMake(frameCount,(int32_t) 5);

                append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
                CVPixelBufferPoolRef bufferPool = adaptor.pixelBufferPool;
                NSParameterAssert(bufferPool != NULL);

                [NSThread sleepForTimeInterval:0.05];
            }
            else
            {
                printf("adaptor not ready %d, %d\n", frameCount, j);
                [NSThread sleepForTimeInterval:0.1];
            }
            j++;
        }
        if (!append_ok)
        {
            printf("error appending image %d times %d\n", frameCount, j);
        }
        frameCount++;
        CVBufferRelease(buffer);
    }

    [videoWriterInput markAsFinished];
    [videoWriter finishWriting];

    [arrSelectedImgs removeAllObjects];

    NSLog(@"Write Ended at path == %@",path);

    [self createGIFFromVideoURL:[NSURL URLWithString:path]];

    [self viewMovieAtUrl:[NSURL URLWithString:path]];
}

- (CVPixelBufferRef) pixelBufferFromCGImage:(CGImageRef)image size:(CGSize)size
{
    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);
    status=status;//Added to make the stupid compiler not show a stupid warning.
    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

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

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pxdata, size.width,
                                                 size.height, 8, 4*size.width, rgbColorSpace,
                                                 kCGImageAlphaNoneSkipFirst);
    NSParameterAssert(context);

    //CGContextTranslateCTM(context, 0, CGImageGetHeight(image));
    //CGContextScaleCTM(context, 1.0, -1.0);//Flip vertically to account for different origin

    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
                                           CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}

Thanks in advance.