В настоящее время я работаю над приложением для iOS, которое объединяет желаемое количество видео. Когда пользователь нажимает кнопку, чтобы объединить видео, видео объединяются и затем воспроизводятся с использованием AVPlayer как:

CMTime nextClipStartTime = kCMTimeZero;
NSInteger i;
CMTime transitionDuration = CMTimeMake(1, 1); // Default transition duration is one second.

// Add two video tracks and two audio tracks.
AVMutableCompositionTrack *compositionVideoTracks[2];
AVMutableCompositionTrack *compositionAudioTracks[2];
compositionVideoTracks[0] = [self.mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
compositionVideoTracks[1] = [self.mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
compositionAudioTracks[0] = [self.mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
compositionAudioTracks[1] = [self.mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

CMTimeRange *passThroughTimeRanges = alloca(sizeof(CMTimeRange) * [self.selectedAssets count]);
CMTimeRange *transitionTimeRanges = alloca(sizeof(CMTimeRange) * [self.selectedAssets count]);

// Place clips into alternating video & audio tracks in composition, overlapped by transitionDuration.
for (i = 0; i < [self.selectedAssets count]; i++ )
{
    NSInteger alternatingIndex = i % 2; // alternating targets: 0, 1, 0, 1, ...
    AVURLAsset *asset = [self.selectedAssets objectAtIndex:i];

    NSLog(@"number of tracks %d",asset.tracks.count);

    CMTimeRange assetTimeRange;
    assetTimeRange.start = kCMTimeZero;
    assetTimeRange.duration = asset.duration;
    NSValue *clipTimeRange = [NSValue valueWithCMTimeRange:assetTimeRange];
    CMTimeRange timeRangeInAsset;
    if (clipTimeRange)
        timeRangeInAsset = [clipTimeRange CMTimeRangeValue];
    else
        timeRangeInAsset = CMTimeRangeMake(kCMTimeZero, [asset duration]);

    AVAssetTrack *clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    [compositionVideoTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipVideoTrack atTime:nextClipStartTime error:nil];

    AVAssetTrack *clipAudioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    [compositionAudioTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipAudioTrack atTime:nextClipStartTime error:nil];

    // Remember the time range in which this clip should pass through.
    // Every clip after the first begins with a transition.
    // Every clip before the last ends with a transition.
    // Exclude those transitions from the pass through time ranges.
    passThroughTimeRanges[i] = CMTimeRangeMake(nextClipStartTime, timeRangeInAsset.duration);
    if (i > 0) {
        passThroughTimeRanges[i].start = CMTimeAdd(passThroughTimeRanges[i].start, transitionDuration);
        passThroughTimeRanges[i].duration = CMTimeSubtract(passThroughTimeRanges[i].duration, transitionDuration);
    }
    if (i+1 < [self.selectedAssets count]) {
        passThroughTimeRanges[i].duration = CMTimeSubtract(passThroughTimeRanges[i].duration, transitionDuration);
    }

    // The end of this clip will overlap the start of the next by transitionDuration.
    // (Note: this arithmetic falls apart if timeRangeInAsset.duration < 2 * transitionDuration.)
    nextClipStartTime = CMTimeAdd(nextClipStartTime, timeRangeInAsset.duration);
    nextClipStartTime = CMTimeSubtract(nextClipStartTime, transitionDuration);

    // Remember the time range for the transition to the next item.
    transitionTimeRanges[i] = CMTimeRangeMake(nextClipStartTime, transitionDuration);
}

// Set up the video composition if we are to perform crossfade or push transitions between clips.
NSMutableArray *instructions = [NSMutableArray array];

// Cycle between "pass through A", "transition from A to B", "pass through B", "transition from B to A".
for (i = 0; i < [self.selectedAssets count]; i++ )
{
    NSInteger alternatingIndex = i % 2; // alternating targets

    // Pass through clip i.
    AVMutableVideoCompositionInstruction *passThroughInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    passThroughInstruction.timeRange = passThroughTimeRanges[i];
    AVMutableVideoCompositionLayerInstruction *passThroughLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[alternatingIndex]];

    passThroughInstruction.layerInstructions = [NSArray arrayWithObject:passThroughLayer];
    [instructions addObject:passThroughInstruction];

    AVMutableVideoCompositionLayerInstruction *fromLayer;

    AVMutableVideoCompositionLayerInstruction *toLayer;

    if (i+1 < [self.selectedAssets count])
    {
        // Add transition from clip i to clip i+1.

        AVMutableVideoCompositionInstruction *transitionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
        transitionInstruction.timeRange = transitionTimeRanges[i];
        fromLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[alternatingIndex]];
        toLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[1-alternatingIndex]];


        // Fade out the fromLayer by setting a ramp from 1.0 to 0.0.
        [fromLayer setOpacityRampFromStartOpacity:1.0 toEndOpacity:0.0 timeRange:transitionTimeRanges[i]];

        transitionInstruction.layerInstructions = [NSArray arrayWithObjects:fromLayer, toLayer, nil];
        [instructions addObject:transitionInstruction];



    }

    AVURLAsset *sourceAsset = [AVURLAsset URLAssetWithURL:[self.selectedItemsURL objectAtIndex:i] options:[NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:AVURLAssetPreferPreciseDurationAndTimingKey]];

    AVAssetTrack *sourceVideoTrack = [[sourceAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];



    CGSize temp = CGSizeApplyAffineTransform(sourceVideoTrack.naturalSize, sourceVideoTrack.preferredTransform);
    CGSize size = CGSizeMake(fabsf(temp.width), fabsf(temp.height));
    CGAffineTransform transform = sourceVideoTrack.preferredTransform;

    self.videoComposition.renderSize = sourceVideoTrack.naturalSize;
    if (size.width > size.height) {

        [fromLayer setTransform:transform atTime:sourceAsset.duration];
    } else {


        float s = size.width/size.height;


        CGAffineTransform new = CGAffineTransformConcat(transform, CGAffineTransformMakeScale(s,s));

        float x = (size.height - size.width*s)/2;

        CGAffineTransform newer = CGAffineTransformConcat(new, CGAffineTransformMakeTranslation(x, 0));

        [fromLayer setTransform:newer atTime:sourceAsset.duration];
    }



}

self.videoComposition.instructions = instructions;

self.videoComposition.frameDuration = CMTimeMake(1, 30);



NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"mergeVideo-%d.mov",arc4random() % 1000]];

NSURL *url = [NSURL fileURLWithPath:myPathDocs];

self.exporter = [[AVAssetExportSession alloc] initWithAsset:self.mixComposition presetName:AVAssetExportPresetMediumQuality];
self.exporter.outputURL=url;
self.exporter.outputFileType = AVFileTypeQuickTimeMovie;
self.exporter.videoComposition = self.videoComposition;
self.exporter.shouldOptimizeForNetworkUse = YES;

self.playerItem = [AVPlayerItem playerItemWithAsset:self.mixComposition];
self.playerItem.videoComposition = self.videoComposition;
AVPlayer *player = [AVPlayer playerWithPlayerItem:self.playerItem];
AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
[playerLayer setFrame:CGRectMake(0, 0, self.imageView.frame.size.width, self.imageView.frame.size.height)];
[[[self imageView] layer] addSublayer:playerLayer];
playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[player play];

[[NSNotificationCenter defaultCenter]
 addObserver:self selector:@selector(checkPlayEnded) name:AVPlayerItemDidPlayToEndTimeNotification object:self.playerItem];

В настоящее время я сталкиваюсь со следующими проблемами:

Если одно видео находится в портретной ориентации, а другое - в альбомной, как я смогу повернуть портретное видео в альбомной ориентации, поскольку мой вид находится в альбомной ориентации, но портретное видео сохраняет свой исходный вид? (Я загружаю видео, хранящиеся в рулоне камеры, а не записываю их в моем приложении)

Пренебрегая вышеупомянутой проблемой, если я объединяю любое количество видео, они работают хорошо. Как только я сохраняю это новое видео в своей библиотеке, а затем снова загружаю его в свое приложение и пытаюсь соединить это видео с каким-то другим новым видео, разрешение становится нарушенным, хотя оба видео, если они воспроизводятся отдельно в приложении, работают действительно хорошо. Как я могу решить это?

(Я пытался следовать учебному пособию по редактированию видео WWDC 2010, поэтому этот код извлечен оттуда.)