使用AVAssetExportSession时崩溃

Question

我使用AVAssetExportSession保存带有水印的视频link

但我的应用程序崩溃了： [exporter exportAsynchronouslyWithCompletionHandler：^ {}];

我的代码：

- (void)mixVideoAsset{
    AVAsset *videoAsset = [AVAsset assetWithURL:_urlVideo];

    // 2 - Create AVMutableComposition object. This object will hold your AVMutableCompositionTrack instances.
    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];

    // 3 - Video track
    AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                        preferredTrackID:kCMPersistentTrackID_Invalid];
    [videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                        ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
                         atTime:kCMTimeZero error:nil];

    // - Audio
    AVMutableCompositionTrack *audioCompositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    AVAssetTrack *audioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    [audioCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioTrack.timeRange.duration) ofTrack:audioTrack atTime:kCMTimeZero error:nil];

    // 3.1 - Create AVMutableVideoCompositionInstruction
    AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);

    // 3.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
    AVAssetTrack *videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    BOOL isVideoAssetPortrait_  = NO;
    CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
    if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
        isVideoAssetPortrait_ = YES;
    }
    if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
        isVideoAssetPortrait_ = YES;
    }

    [videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
    [videolayerInstruction setOpacity:0.0 atTime:videoAsset.duration];

    // 3.3 - Add instructions
    mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

    AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

    CGSize naturalSize;
    if(isVideoAssetPortrait_){
        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
    } else {
        naturalSize = videoAssetTrack.naturalSize;
    }

    float renderWidth, renderHeight;
    renderWidth = naturalSize.width;
    renderHeight = naturalSize.height;
    mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
    mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
    mainCompositionInst.frameDuration = CMTimeMake(1, 30);


    [self applyVideoEffectsToComposition:mainCompositionInst size:naturalSize];


    // 5 - Create exporter
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                      presetName:AVAssetExportPresetHighestQuality];
    NSString *exportPath = [PATH_VIDEO_FOLDER stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.mov",[VideoHelper getVideoDateByDate:[NSDate date]]]];
    CMTime start = CMTimeMakeWithSeconds(mySAVideoRangeSlider.leftPosition, videoAsset.duration.timescale);
    CMTime duration = CMTimeMakeWithSeconds(VIDEO_TIME_TRIM_SECONDS, videoAsset.duration.timescale);
    CMTimeRange range = CMTimeRangeMake(start, duration);
    exporter.timeRange = range;

    exporter.outputURL = [NSURL fileURLWithPath:exportPath];
    exporter.outputFileType = AVFileTypeQuickTimeMovie;
//    exporter.shouldOptimizeForNetworkUse = YES;
    exporter.videoComposition = mainCompositionInst;

    [exporter exportAsynchronouslyWithCompletionHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Export Complete %ld %@", (long)exporter.status, exporter.error);
            [VideoHelper saveThumbnailByVideoURL:[NSURL fileURLWithPath:exportPath]];
        });
    }];
}

applyVideoEffectsToComposition

- (void)applyVideoEffectsToComposition:(AVMutableVideoComposition *)composition size:(CGSize)size
{

    // - set up the parent layer
    CALayer *parentLayer = [CALayer layer];
    CALayer *videoLayer = [CALayer layer];
    parentLayer.frame = CGRectMake(0, 0, size.width, size.height);
    videoLayer.frame = CGRectMake(0, 0, size.width, size.height);
    [parentLayer addSublayer:videoLayer];

    // - set up the overlay
    CALayer *overlayLayer = [CALayer layer];
    overlayLayer.frame = CGRectMake(0, 0, size.width, size.height);

    CAKeyframeAnimation *animation = [self animationForGifWithURL:urlEffect];
    [overlayLayer addAnimation:animation forKey:@"contents"];

    [parentLayer addSublayer:overlayLayer];

    // - apply magic
    composition.animationTool = [AVVideoCompositionCoreAnimationTool
                                 videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

}

animationForGifWithURL

- (CAKeyframeAnimation *)animationForGifWithURL:(NSURL *)url {

    CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];

    NSMutableArray * frames = [NSMutableArray new];
    NSMutableArray *delayTimes = [NSMutableArray new];

    CGFloat totalTime = 0.0;

    CGImageSourceRef gifSource = CGImageSourceCreateWithURL((CFURLRef)url, NULL);

    // get frame count
    size_t frameCount = CGImageSourceGetCount(gifSource);
    for (size_t i = 0; i < frameCount; ++i) {
        // get each frame
        CGImageRef frame = CGImageSourceCreateImageAtIndex(gifSource, i, NULL);
        [frames addObject:(__bridge id)frame];
        CGImageRelease(frame);

        // get gif info with each frame
        NSDictionary *dict = (NSDictionary*)CFBridgingRelease(CGImageSourceCopyPropertiesAtIndex(gifSource, i, NULL));

        // kCGImagePropertyGIFDictionary中kCGImagePropertyGIFDelayTime，kCGImagePropertyGIFUnclampedDelayTime值是一样的
        NSDictionary *gifDict = [dict valueForKey:(NSString*)kCGImagePropertyGIFDictionary];
        [delayTimes addObject:[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime]];

        totalTime = totalTime + [[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime] floatValue];

        CFRelease((__bridge CFTypeRef)(dict));
    }

    if (gifSource) {
        CFRelease(gifSource);
    }

    NSMutableArray *times = [NSMutableArray arrayWithCapacity:3];
    CGFloat currentTime = 0;
    NSInteger count = delayTimes.count;
    for (int i = 0; i < count; ++i) {
        [times addObject:[NSNumber numberWithFloat:(currentTime / totalTime)]];
        currentTime += [[delayTimes objectAtIndex:i] floatValue];
    }

    NSMutableArray *images = [NSMutableArray arrayWithCapacity:3];
    for (int i = 0; i < count; ++i) {
        [images addObject:[frames objectAtIndex:i]];
    }

    animation.keyTimes = times;
    animation.values = images;
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    animation.duration = totalTime;
    animation.repeatCount = HUGE_VALF;

    animation.beginTime = AVCoreAnimationBeginTimeAtZero;
    animation.removedOnCompletion = NO;

    return animation;
}