gif-encoder.m

#import "ObjCRootViewController.h"
@import AVFoundation;
@import MobileCoreServices;
@import Photos;

@interface ObjCRootViewController ()

@end

@implementation ObjCRootViewController

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    
    [self startVideoToGIFProgess];
}

- (void)startVideoToGIFProgess {
    NSLog(@"Downloading!");
    
    NSString *urlString = @"https://v.redd.it/naxqsasl2nn41/DASH_720?source=fallback";
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]];
    NSString *fileName = [NSString stringWithFormat:@"%@_%@", [[NSProcessInfo processInfo] globallyUniqueString], @"html5gif.mp4"];
    NSURL *fileURL = [[NSURL fileURLWithPath:NSTemporaryDirectory()] URLByAppendingPathComponent:fileName];
    [data writeToURL:fileURL atomically:YES];
    
    NSLog(@"Downloaded!");
    
    [self createGIFFromVideoAtURL:fileURL];
}

- (void)createGIFFromVideoAtURL:(NSURL *)URL {
    CFTimeInterval startTime = CACurrentMediaTime();
    
    AVURLAsset *asset = [AVURLAsset assetWithURL:URL];
    AVAssetReader *reader = [AVAssetReader assetReaderWithAsset:asset error:nil];
    AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] firstObject];
    
    NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                            [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey,
                                          [NSNumber numberWithInt:328], kCVPixelBufferWidthKey,
                                          [NSNumber numberWithInt:480], kCVPixelBufferHeightKey,
                                            nil];
    
    AVAssetReaderTrackOutput* readerOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:videoTrack outputSettings:outputSettings];

    [reader addOutput:readerOutput];
    [reader startReading];
    
    CMSampleBufferRef sample = [readerOutput copyNextSampleBuffer];
    CGFloat delayBetweenFrames = 0.033333;
    
    NSDictionary *fileProperties = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount] forKey:(NSString *)kCGImagePropertyGIFDictionary];
    
    NSDictionary *frameProperties = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:delayBetweenFrames] forKey:(NSString *)kCGImagePropertyGIFDelayTime] forKey:(NSString *)kCGImagePropertyGIFDictionary];
    
    NSString *resultingFilename = [NSString stringWithFormat:@"%@_%@", [[NSProcessInfo processInfo] globallyUniqueString], @"html5gif.gif"];
    NSURL *resultingFileURL = [[NSURL fileURLWithPath:NSTemporaryDirectory()] URLByAppendingPathComponent:resultingFilename];
    
    NSInteger totalFrames = 1086;
    
    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((CFURLRef)resultingFileURL, (CFStringRef)kUTTypeGIF, totalFrames, nil);
    CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)fileProperties);
    
    NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
    operationQueue.maxConcurrentOperationCount = 1;
    
    while (sample) {
        if (sample) {
            CGImageRef cgImage = [self cgImageFromSampleBuffer:sample];
            
            [operationQueue addOperationWithBlock:^{
                CGImageDestinationAddImage(destination, cgImage, (__bridge CFDictionaryRef)frameProperties);
                CGImageRelease(cgImage); // Memory never gets out of control
            }];
        }
        
        CFRelease(sample);
        sample = [readerOutput copyNextSampleBuffer];
    }
    
    [operationQueue waitUntilAllOperationsAreFinished];
    
    CFTimeInterval endTime = CACurrentMediaTime();
    NSLog(@"Total Runtime: %g s", endTime - startTime);
    
    BOOL result = CGImageDestinationFinalize(destination);
    
    NSLog(@"%d did complete", result);
    
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        [PHAssetCreationRequest creationRequestForAssetFromImageAtFileURL:resultingFileURL];
    } completionHandler:^(BOOL success, NSError * _Nullable error) {
        NSLog(@"Saved successfully? %d", success);
    }];
}

- (CGImageRef)cgImageFromSampleBuffer:(CMSampleBufferRef)buffer {
    CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(buffer);
    
    CVPixelBufferLockBaseAddress(pixelBuffer, kCVPixelBufferLock_ReadOnly);
    
    void* baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer);
    
    size_t width = CVPixelBufferGetWidth(pixelBuffer);
    size_t height = CVPixelBufferGetHeight(pixelBuffer);
    
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedFirst);
    
    CGImageRef image = CGBitmapContextCreateImage(context);
    
    CVPixelBufferUnlockBaseAddress(pixelBuffer, kCVPixelBufferLock_ReadOnly);
    CGContextRelease(context);
    
    return image;
}

@end