AVMovieExporter/AssetItem.m

/*
     File: AssetItem.m
 Abstract: Model object that stores information about an asset such as its metadata, track information, and allows it to be exported.
  Version: 1.0
 
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 */
 
 
#import "AssetItem.h"
#import "VideoLibrary.h"
 
#import <MobileCoreServices/MobileCoreServices.h>
 
@interface AssetItem ()
 
@property(readonly, strong) AVAssetImageGenerator *imageGenerator;
 
@property(readonly, strong) AVAsset *videoAsset;
@property(readonly, unsafe_unretained) dispatch_once_t titleToken;
@property(readonly, unsafe_unretained) dispatch_once_t thumbnailToken;
@property(readonly, unsafe_unretained) dispatch_once_t metadataToken;
@property(readonly, unsafe_unretained) dispatch_once_t tracksToken;
 
@property(readwrite, unsafe_unretained) BOOL writingFile;
 
@end
 
@implementation AssetItem
 
@synthesize imageGenerator = _imageGenerator;
@synthesize exportSession = _exportSession;
@synthesize progressLabel = _progressLabel;
@synthesize finishedExport = _finishedExport;
@synthesize assetURL = _assetURL;
@synthesize title = _title;
@synthesize videoAsset = _videoAsset;
@synthesize metadata = _metadata;
@synthesize tracks = _tracks;
@synthesize thumbnail = _thumbnail;
 
@synthesize titleToken = _titleToken;
@synthesize thumbnailToken = _thumbnailToken;
@synthesize metadataToken = _metadataToken;
@synthesize tracksToken = _tracksToken;
 
@synthesize writingFile = _writingFile;
 
- (id)initWithURL:(NSURL *)url
{
    self = [super init];
    if (self) 
    {
        _assetURL = url;
        _videoAsset = [[AVURLAsset alloc] initWithURL:self.assetURL options:nil];
        _imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:_videoAsset];
        
        _title = [[_assetURL lastPathComponent] copy];
        _metadata = [NSMutableArray array];
        _thumbnail = [UIImage imageNamed:@"Browser-ErrorLoading"];
        _writingFile = NO;
    }
    
    return self;
}
 
- (BOOL)isEqual:(id)anObject
{
    if ([anObject isKindOfClass:[AssetItem class]])
    {
        AssetItem *assetObject = (AssetItem *)anObject;
        return [self.assetURL isEqual:assetObject.assetURL];
    }
    else
    {
        return NO;
    }
}
 
- (NSUInteger)hash
{
    return [self.assetURL hash];
}
 
#pragma mark - Load Asset Information
 
- (void)loadMetadataWithCompletionHandler:(void (^)(void))completionHandler
{
    __unsafe_unretained __block AssetItem *weakSelf = (AssetItem *)self;
    dispatch_once(&_metadataToken, ^{
        // Add metadata from all metadata formats
        NSLog(@"Loading metadata...");
        NSArray *keys = [[NSArray alloc] initWithObjects:@"commonMetadata", nil];
        [weakSelf.videoAsset loadValuesAsynchronouslyForKeys:keys completionHandler:^{
            
            [weakSelf.metadata removeAllObjects];
            for (NSString *format in [weakSelf.videoAsset availableMetadataFormats])
                [weakSelf.metadata addObjectsFromArray:[weakSelf.videoAsset metadataForFormat:format]];
            
            dispatch_async(dispatch_get_main_queue(), ^{
                completionHandler();
            });
        }];
    });
}
 
- (void)loadTracksWithCompletionHandler:(void (^)(void))completionHandler
{
    __unsafe_unretained __block AssetItem *weakSelf = (AssetItem *)self;
    dispatch_once(&_tracksToken, ^{
        NSLog(@"Loading tracks for %@...", weakSelf.title);
        NSArray *keys = [[NSArray alloc] initWithObjects:@"tracks", nil];
        [weakSelf.videoAsset loadValuesAsynchronouslyForKeys:keys completionHandler:^{
            
            [weakSelf resetExport];
            
            dispatch_async(dispatch_get_main_queue(), ^{
                completionHandler();
            });
        }];
    });
}
 
// Load the first frame of the video for a thumbnail
- (UIImage *)loadThumbnailWithCompletionHandler:(void (^)(void))completionHandler
{
    __unsafe_unretained __block AssetItem *weakSelf = (AssetItem *)self;
    dispatch_once(&_thumbnailToken, ^{
        [weakSelf.imageGenerator generateCGImagesAsynchronouslyForTimes:[NSArray arrayWithObject:[NSValue valueWithCMTime:kCMTimeZero]] 
                                                      completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error) {
            if (result == AVAssetImageGeneratorSucceeded)
            {
                weakSelf.thumbnail = [UIImage imageWithCGImage:image];
                dispatch_async(dispatch_get_main_queue(), ^{
                    NSLog(@"Loaded thumbnail for %@", weakSelf.title);
                    completionHandler();
                });
            }
            else if (result == AVAssetImageGeneratorFailed)
            {
                NSLog(@"couldn't generate thumbnail, error:%@", error);
            }
        }];
    });
    
    return self.thumbnail;
}
 
- (NSString *)loadTitleWithCompletionHandler:(void (^)(void))completionHandler
{
    __unsafe_unretained __block AssetItem *weakSelf = (AssetItem *)self;
    dispatch_once(&_titleToken, ^{
        // Load the title from AVMetadataCommonKeyTitle
        NSLog(@"Loading title...");
        NSArray *key = [[NSArray alloc] initWithObjects:@"commonMetadata", nil];
        [weakSelf.videoAsset loadValuesAsynchronouslyForKeys:key 
                                       completionHandler:^{
            NSArray *titles = [AVMetadataItem metadataItemsFromArray:weakSelf.videoAsset.commonMetadata withKey:AVMetadataCommonKeyTitle keySpace:AVMetadataKeySpaceCommon];
            if ([titles count] > 0)
            {
                // If there is only one title, then use it
                if ([titles count] == 1)
                {
                    AVMetadataItem *titleItem = [titles objectAtIndex:0];
                    weakSelf.title = [titleItem stringValue];
                    dispatch_async(dispatch_get_main_queue(), ^{
                        NSLog(@"Loaded title for %@", weakSelf.title);
                        completionHandler();
                    });
                }
                else
                {
                    // If there are more than one, search for the proper locale
                    NSArray *preferredLanguages = [NSLocale preferredLanguages];
                    for (NSString *currentLanguage in preferredLanguages)
                    {
                        NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:currentLanguage];
                        NSArray *titlesForLocale = [AVMetadataItem metadataItemsFromArray:titles withLocale:locale];
                        if ([titlesForLocale count] > 0)
                        {
                            weakSelf.title = [[titlesForLocale objectAtIndex:0] stringValue];
                            dispatch_async(dispatch_get_main_queue(), ^{
                                NSLog(@"Loaded title for %@", weakSelf.title);
                                completionHandler();
                            });
                            break;
                        }
                    }
                }
            }
        }];
    });
 
    return self.title;
}
 
#pragma mark - Metadata
 
// Report the metadata status while it is loading
- (NSString *)metadataLabelAtIndex:(NSUInteger)index
{
    NSString *metadataLabel = nil;
    
    // Get the status of the commonMetadata key
    NSError *error = nil;
    AVKeyValueStatus metadataLoadingStatus = [self.videoAsset statusOfValueForKey:@"commonMetadata" error:&error];
    if (metadataLoadingStatus == AVKeyValueStatusLoading)
    {
        metadataLabel = @"Loading metadata...";
    }
    else if (metadataLoadingStatus == AVKeyValueStatusFailed)
    {
        metadataLabel = @"Loading metadata failed!";
        NSLog(@"%@", error);
    }
    else if (metadataLoadingStatus == AVKeyValueStatusLoaded)
    {
        // When the metadata is loaded
        if (self.metadata.count > 0)
        {
            AVMetadataItem *metadataItem = [self.metadata objectAtIndex:index];
            
            if (metadataItem.commonKey != nil)
                metadataLabel = metadataItem.commonKey;
            else
                metadataLabel = [AssetItem stringFromKeyOfMetadataItem:metadataItem];
        }
    }
    
    return metadataLabel;
}
 
// Convert a four character code to an NSString
+ (NSString *)stringFromKeyOfMetadataItem:(AVMetadataItem *)metadataItem
{
    NSString *key = nil;
    if ([metadataItem.key isKindOfClass:[NSNumber class]])
    {
        NSInteger longValue = [(NSNumber *)metadataItem.key longValue];
        char *charSource = (char *)&longValue;
        char charValue[4] = {0};
        charValue[0] = charSource[3];
        charValue[1] = charSource[2];
        charValue[2] = charSource[1];
        charValue[3] = charSource[0];
        key = [[NSString alloc] initWithBytes:charValue length:4 encoding:NSASCIIStringEncoding];
    }
    else
    {
        key = [metadataItem.key description];
    }
    
    return key;
}
 
#pragma mark - Tracks
 
- (NSArray *)tracks
{
    return self.videoAsset.tracks;
}
 
// Report the track status while it is loading
- (NSString *)trackLabelAtIndex:(NSUInteger)index
{
    NSString *trackLabel = nil;
    
    // Get the status of the tracks key
    NSError *error = nil;
    AVKeyValueStatus trackLoadingStatus = [self.videoAsset statusOfValueForKey:@"tracks" error:&error];
    if (trackLoadingStatus == AVKeyValueStatusLoading)
    {
        trackLabel = @"Loading track...";
    }
    else if (trackLoadingStatus == AVKeyValueStatusFailed)
    {
        trackLabel = @"Loading track failed!";
        NSLog(@"%@", error);
    }
    else if (trackLoadingStatus == AVKeyValueStatusLoaded)
    {
        // When the tracks are loaded
        if (self.tracks.count > 0)
        {
            AVAssetTrack *track = [self.tracks objectAtIndex:index];
            trackLabel = NSLocalizedString(track.mediaType , nil);
        }
    }
    
    return trackLabel;
}
 
#pragma mark - Export Information
 
// Get the presets that are compatible with the AVAsset
- (NSArray *)supportedPresets
{
    NSMutableArray *presets = [NSMutableArray arrayWithArray:[AVAssetExportSession exportPresetsCompatibleWithAsset:self.videoAsset]];
    [presets removeObject:AVAssetExportPresetAppleM4A]; // Remove M4A because we are writing to the AssetLibrary.
    return [presets sortedArrayUsingComparator:^(id obj1, id obj2) {
        NSString *string1 = (NSString *)obj1;
        NSString *string2 = (NSString *)obj2;
        return [string1 compare:string2];
    }];
}
 
// Get the file types that are compatible with the preset and AVAsset combination
- (NSArray *)supportedFileTypes
{
    return [[self.exportSession supportedFileTypes] sortedArrayUsingComparator:^(id obj1, id obj2) {
        NSString *string1 = (NSString *)obj1;
        NSString *string2 = (NSString *)obj2;
        return [string1 compare:string2];
    }];
}
 
- (NSString *)preset
{
    return self.exportSession.presetName;
}
 
// When we change the preset we have to re-create the AVAssetExportSession
- (void)setPreset:(NSString *)preset
{
    if (self.exportSession == nil || ![self.exportSession.presetName isEqualToString:preset])
    {
        AVAssetExportSession *oldExportSession = self.exportSession;
        [oldExportSession cancelExport];
        
        // Create the new AVAssetExportSession and copy over the old properties
        AVAssetExportSession *temp = [[AVAssetExportSession alloc] initWithAsset:self.videoAsset presetName:preset];
        self.exportSession = temp;
        if (oldExportSession != nil)
        {
            NSArray *supportedFileTypes = self.supportedFileTypes;
            if ([supportedFileTypes containsObject:oldExportSession.outputFileType])
                self.exportSession.outputFileType = oldExportSession.outputFileType;
            else
                self.exportSession.outputFileType = [supportedFileTypes objectAtIndex:0];
                
            self.exportSession.shouldOptimizeForNetworkUse = oldExportSession.shouldOptimizeForNetworkUse;
        }
    }
}
 
#pragma mark - Performing Exports
 
- (void)exportAssetWithCompletionHandler:(void (^)(NSError *error))completionHandler
{
    // Choose a unique file name
    NSUInteger count = 0;
    NSString *filePath = nil;
    do {
        NSString *extension = (__bridge_transfer NSString *)UTTypeCopyPreferredTagWithClass((__bridge CFStringRef)self.exportSession.outputFileType, kUTTagClassFilenameExtension);
        NSString *fileNameNoExtension = [[self.assetURL URLByDeletingPathExtension] lastPathComponent];
        NSString *fileName = [NSString stringWithFormat:@"%@-%@-%lu",fileNameNoExtension , [self preset], count];
        filePath = NSTemporaryDirectory();
        filePath = [filePath stringByAppendingPathComponent:fileName];
        filePath = [filePath stringByAppendingPathExtension:extension];
        count++;
        
    } while ([[NSFileManager defaultManager] fileExistsAtPath:filePath]);
    
    NSURL *outputURL = [NSURL fileURLWithPath:filePath];
    
    // Set up the AVAssetExportSession
    self.exportSession.metadata = [self.metadata copy];
    self.exportSession.outputURL = outputURL;
    
    __unsafe_unretained __block AssetItem *weakSelf = (AssetItem *)self;
    [self.exportSession exportAsynchronouslyWithCompletionHandler:^{
        if (weakSelf.exportSession.status == AVAssetExportSessionStatusFailed)
        {
            completionHandler(weakSelf.exportSession.error);
        }
        else if (weakSelf.exportSession.status == AVAssetExportSessionStatusCompleted)
        {
            weakSelf.writingFile = YES;
            [VideoLibrary saveMovieAtPathToAssetLibrary:outputURL withCompletionHandler:^(NSError *error){
                dispatch_async(dispatch_get_main_queue(), ^{
                    weakSelf.writingFile = NO;
                    completionHandler(error);
                });
            }];
        }
    }];
}
 
- (void)resetExport
{
    [self.exportSession cancelExport];
    self.exportSession = nil;
    self.preset = AVAssetExportPresetMediumQuality;
    self.exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    self.exportSession.shouldOptimizeForNetworkUse = NO;
}
 
- (NSString *)progressLabel
{
    NSString *label = nil;
    
    if (self.writingFile)
    {
        label = @"Writing file to Asset Library";
    }
    else
    {
        switch (self.exportSession.status) {
            case AVAssetExportSessionStatusCancelled:
                label = @"Export Cancelled";
                break;
            case AVAssetExportSessionStatusExporting:
                label = @"Exporting...";
                break;
            case AVAssetExportSessionStatusCompleted:
                label = @"Export Completed!";
                break;
            case AVAssetExportSessionStatusFailed:
                label = @"Export Failed!";
                break;
            case AVAssetExportSessionStatusWaiting:
                label = @"Waiting to export...";
                break;
            case AVAssetExportSessionStatusUnknown:
                label = @"Export has not started";
                break;
                
            default:
                break;
        }
    }
    
    return label;
}
 
- (BOOL)finishedExport
{
    BOOL finishedExport = NO;
    AVAssetExportSessionStatus status = self.exportSession.status;
    
    if (!self.writingFile && 
        (status == AVAssetExportSessionStatusCancelled || 
        status == AVAssetExportSessionStatusCompleted || 
        status == AVAssetExportSessionStatusFailed))
        finishedExport = YES;
    
    return finishedExport;
}
 
@end


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