How to Animate Images while converting to Video

Question

I want to animate images smoothly while converting them to video. Dispite of searching SO, I am unable to understand how to achive it. I tried changing the Rotation angle(CGAffineTransformRotation), Translations and Scaling but didn't found a way to for the smooth animations. Heres how I am converting array of photos to video :

- (void)createVideoWithArrayImages:(NSMutableArray*)images size:(CGSize)size time:(float)time output:(NSURL*)output {
    //getting a random path
    NSError *error;

    AVAssetWriter *videoWriter  = [[AVAssetWriter alloc] initWithURL:output fileType:AVFileTypeMPEG4 error: &error];
    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];

    videoWriterInput.expectsMediaDataInRealTime = YES;
    [videoWriter addInput: videoWriterInput];
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];


    CVPixelBufferRef buffer = NULL;
    //convert uiimage to CGImage.

    //convert uiimage to CGImage.
    NSInteger fps   = 30;
    int frameCount  = 0;

    for(UIImage *img  in images) {
        //for(VideoFrame * frm in imageArray)
        NSLog(@"**************************************************");
        //UIImage * img = frm._imageFrame;
        buffer                          = [self videoPixelBufferFromCGImage:[img CGImage] andSize:size andAngle:(int)[images indexOfObject:img]];
        double numberOfSecondsPerFrame  = time / images.count;
        double frameDuration            = fps * numberOfSecondsPerFrame;

        BOOL append_ok  = NO;
        int j           = 0;

        while (!append_ok && j < fps) {
            if (adaptor.assetWriterInput.readyForMoreMediaData) {
                //print out status:
                NSLog(@"Processing video frame (%d,%d)",frameCount,(int)[images count]);

                CMTime frameTime    = CMTimeMake(frameCount * frameDuration,(int32_t) fps);
                NSLog(@"Frame Time  : %f", CMTimeGetSeconds(frameTime));
                append_ok           = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
                if(!append_ok) {
                    NSError *error = videoWriter.error;
                    if(error!=nil) {
                        NSLog(@"Unresolved error %@,%@.", error, [error userInfo]);
                    }
                }
            }
            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, with error.", frameCount, j);
        }
        frameCount++;
        NSLog(@"**************************************************");
    }

    [videoWriterInput markAsFinished];
    [videoWriter finishWriting];

    videoWriter = nil;
    if(buffer != NULL)
        CVPixelBufferRelease(buffer);
    NSLog(@"************ write standard video successful ************");
}

Here CVPixelBufferRef is returned as follows :

- (CVPixelBufferRef)videoPixelBufferFromCGImage: (CGImageRef) image andSize:(CGSize) size andAngle:(int)angle {
    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);

    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, kCGImageAlphaPremultipliedFirst);
    NSParameterAssert(context);
    CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
    CGContextDrawImage(context, CGRectMake(0, 0, size.width, size.height), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}

I tried adding Translations to the CVPixelBufferRef but thing didn't worked out for me. Any guide, any help would be very useful.

Answer 1

YOu don't specify what you want to achieve, but I've used AVVideoCompositionCoreAnimationTool to include animated CALayers in a AVMutableVideoComposition.

Here is the reference to that class

Hope that helps!