AVMutableVideoComposition rotated video captured in portrait mode

Question

I have used below code to add image overlay over video and then export the new generated video to document directory. But strangely,video gets rotated by 90 degrees.

- (void)buildTransitionComposition:(AVMutableComposition *)composition andVideoComposition:(AVMutableVideoComposition *)videoComposition
{
    CMTime nextClipStartTime = kCMTimeZero;
    NSInteger i;

    // Make transitionDuration no greater than half the shortest clip duration.
    CMTime transitionDuration = self.transitionDuration;
    for (i = 0; i < [_clips count]; i++ ) {
        NSValue *clipTimeRange = [_clipTimeRanges objectAtIndex:i];
        if (clipTimeRange) {
            CMTime halfClipDuration = [clipTimeRange CMTimeRangeValue].duration;
            halfClipDuration.timescale *= 2; // You can halve a rational by doubling its denominator.
            transitionDuration = CMTimeMinimum(transitionDuration, halfClipDuration);
        }
    }

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

    CMTimeRange *passThroughTimeRanges = alloca(sizeof(CMTimeRange) * [_clips count]);
    CMTimeRange *transitionTimeRanges = alloca(sizeof(CMTimeRange) * [_clips count]);

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

        /*
        CGAffineTransform t = clipVideoTrack.preferredTransform;
        NSLog(@"Transform1 : %@",t);
        */
        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 < [_clips 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 < [_clips 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]];
        /*
        CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(M_PI_2);
        CGAffineTransform rotateTranslate = CGAffineTransformTranslate(rotationTransform,320,0);
        [passThroughLayer setTransform:rotateTranslate atTime:kCMTimeZero];
         */
        passThroughInstruction.layerInstructions = [NSArray arrayWithObject:passThroughLayer];
        [instructions addObject:passThroughInstruction];

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

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

            if (self.transitionType == SimpleEditorTransitionTypeCrossFade) {
                // Fade out the fromLayer by setting a ramp from 1.0 to 0.0.
                [fromLayer setOpacityRampFromStartOpacity:1.0 toEndOpacity:0.0 timeRange:transitionTimeRanges[i]];
            }
            else if (self.transitionType == SimpleEditorTransitionTypePush) {
                // Set a transform ramp on fromLayer from identity to all the way left of the screen.
                [fromLayer setTransformRampFromStartTransform:CGAffineTransformIdentity toEndTransform:CGAffineTransformMakeTranslation(-composition.naturalSize.width, 0.0) timeRange:transitionTimeRanges[i]];
                // Set a transform ramp on toLayer from all the way right of the screen to identity.
                [toLayer setTransformRampFromStartTransform:CGAffineTransformMakeTranslation(+composition.naturalSize.width, 0.0) toEndTransform:CGAffineTransformIdentity timeRange:transitionTimeRanges[i]];
            }

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

    videoComposition.instructions = instructions;


}

Please help,as I am not able to export portrait video in proper mode.Any help appreciated. Thank you.

Answer 1

By default, when you export video using AVAssetExportSession then video will be rotated from its original orientation. You have to apply its transform to set it exact orientation.You please try below code to do the same.

- (AVMutableVideoCompositionLayerInstruction *)layerInstructionAfterFixingOrientationForAsset:(AVAsset *)inAsset 
                                                                                     forTrack:(AVMutableCompositionTrack *)inTrack
                                                                                       atTime:(CMTime)inTime
{
    //FIXING ORIENTATION//
    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:inTrack];
    AVAssetTrack *videoAssetTrack = [[inAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;
    BOOL  isVideoAssetPortrait_  = NO;
    CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;

    if(videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0)  {videoAssetOrientation_= UIImageOrientationRight; isVideoAssetPortrait_ = YES;}
    if(videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0)  {videoAssetOrientation_ =  UIImageOrientationLeft; isVideoAssetPortrait_ = YES;}
    if(videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0)   {videoAssetOrientation_ =  UIImageOrientationUp;}
    if(videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {videoAssetOrientation_ = UIImageOrientationDown;}

    CGFloat FirstAssetScaleToFitRatio = 320.0 / videoAssetTrack.naturalSize.width;

    if(isVideoAssetPortrait_) {
        FirstAssetScaleToFitRatio = 320.0/videoAssetTrack.naturalSize.height;
        CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
        [videolayerInstruction setTransform:CGAffineTransformConcat(videoAssetTrack.preferredTransform, FirstAssetScaleFactor) atTime:kCMTimeZero];
    }else{
        CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
        [videolayerInstruction setTransform:CGAffineTransformConcat(CGAffineTransformConcat(videoAssetTrack.preferredTransform, FirstAssetScaleFactor),CGAffineTransformMakeTranslation(0, 160)) atTime:kCMTimeZero];
    }
    [videolayerInstruction setOpacity:0.0 atTime:inTime];
    return videolayerInstruction;
}

I hope this will help you.

AVAssetTrack *assetTrack = [[inAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

AVMutableCompositionTrack *mutableTrack = [mergeComposition mutableTrackCompatibleWithTrack:assetTrack];

AVMutableVideoCompositionLayerInstruction *assetInstruction = [self layerInstructionAfterFixingOrientationForAsset:inAsset forTrack:myLocalVideoTrack atTime:videoTotalDuration];

Above is the code to call mentioned method where inAsset is your video asset and videoTotalDuration is your video total duration in CMTime.mergeComposition is object of AVMutableComposition class.

Hope this will help.

EDIT: This is not any callback method or event, you have to call it expectedly with required parameters as mentioned above.