ios - 即使在应用旋转后，AVMutableComposition 也无法旋转视频

Question

我正在尝试合并和裁剪一系列视频。一切正常，但生成的视频旋转了 90 度。我试图应用旋转变换，但没有任何 react 。我已经查看了至少 4 个其他线程，看看他们的解决方案是什么，而且他们几乎都在做和我一样的事情。我很茫然，知道出了什么问题吗？

- (void)merge {
    if([self.scrollView.buttonArray count] == 0) {
        __block UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Oops!"
                                                        message:@"No films available to fuze!"
                                                       delegate:self
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        dispatch_async(dispatch_get_main_queue(), ^(void){

            [alert show];

        });
    }
    else {
        __block UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Merging"
                                                    message:@"Films are currently fuzing!"
                                                   delegate:self
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles:nil];
        dispatch_async(dispatch_get_main_queue(), ^(void){

            [alert show];

        });
    }
    AVMutableComposition *composition = [AVMutableComposition composition];


    AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

    AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];

    videoComposition.frameDuration = CMTimeMake(1,30);

    videoComposition.renderScale = 1.0;

    AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

    AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];

    AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];


    float time = 0;


    for (VideoButtonView* button in self.scrollView.buttonArray) {


        AVAsset *sourceAsset = button.videoAsset;

        NSError *error = nil;

        id videoTrack = [sourceAsset tracksWithMediaType:AVMediaTypeVideo];
        id audioTrack = [sourceAsset tracksWithMediaType:AVMediaTypeAudio];

        AVAssetTrack *sourceVideoTrack;
        AVAssetTrack *sourceAudioTrack;

        CMTime current_time = [composition duration];

        if(videoTrack) {

            sourceVideoTrack = [videoTrack objectAtIndex:0];
        }
        if(audioTrack) {
            sourceAudioTrack = [audioTrack objectAtIndex:0];
        }

        //crop

        CGSize temp = CGSizeApplyAffineTransform(sourceVideoTrack.naturalSize, sourceVideoTrack.preferredTransform);
        CGSize size = CGSizeMake(fabsf(temp.width), fabsf(temp.height));
        CGAffineTransform transform = sourceVideoTrack.preferredTransform;
        transform = CGAffineTransformRotate(transform, M_PI_2);

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

            [layerInstruction setTransform:transform atTime:CMTimeMakeWithSeconds(time, 30)];
        } 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));

            [layerInstruction setTransform:newer atTime:CMTimeMakeWithSeconds(time, 30)];
        }

        if(videoTrack) {
            [compositionVideoTrack insertTimeRange:sourceVideoTrack.timeRange ofTrack:sourceVideoTrack atTime:current_time error:&error];
        }
        if(audioTrack) {
            [compositionAudioTrack insertTimeRange:sourceAudioTrack.timeRange ofTrack:sourceAudioTrack atTime:current_time error:&error];
        }

        time += CMTimeGetSeconds(sourceVideoTrack.timeRange.duration);

    }
    instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
    instruction.timeRange = compositionVideoTrack.timeRange;


    videoComposition.instructions = [NSArray arrayWithObject:instruction];

    NSString* documentsDirectory= [self applicationDocumentsDirectory];

    NSString* myDocumentPath= [documentsDirectory stringByAppendingPathComponent:@"merge_video.mp4"];

    NSURL *url = [[NSURL alloc] initFileURLWithPath: myDocumentPath];

    if([[NSFileManager defaultManager] fileExistsAtPath:myDocumentPath])

    {

        [[NSFileManager defaultManager] removeItemAtPath:myDocumentPath error:nil];

    }

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];

    exporter.outputURL=url;

    exporter.outputFileType = @"com.apple.quicktime-movie";

    [exporter exportAsynchronouslyWithCompletionHandler:^{
        BOOL success = false;
        switch ([exporter status]) {
            case AVAssetExportSessionStatusCompleted:
                success = true;
                NSLog(@"Export Completed");
                break;
            case AVAssetExportSessionStatusWaiting:
                NSLog(@"Export Waiting");
                break;
            case AVAssetExportSessionStatusExporting:
                NSLog(@"Export Exporting");
                break;
            case AVAssetExportSessionStatusFailed:
            {
                NSError *error = [exporter error];
                NSLog(@"Export failed: %@", [error localizedDescription]);

                break;
            }
            case AVAssetExportSessionStatusCancelled:
                NSLog(@"Export canceled");

                break;
            default:
                break;
        }
        if (success == true) {

            ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init];
            [assetLibrary writeVideoAtPathToSavedPhotosAlbum:url completionBlock:^(NSURL *assetURL, NSError *error){
                NSError *removeError = nil;
                [[NSFileManager defaultManager] removeItemAtURL:url error:&removeError];
            }];
            __block UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Done!"
                                                            message:@"Films have been fuzed!"
                                                           delegate:self
                                                  cancelButtonTitle:@"OK"
                                                  otherButtonTitles:nil];
            dispatch_async(dispatch_get_main_queue(), ^(void){

                [alert show];

            });
        }

    }];
}

Answer 1

AVAssetTrack *assetVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo].lastObject;

// Grab the composition video track from AVMutableComposition you already made.
AVMutableCompositionTrack *compositionVideoTrack = [composition tracksWithMediaType:AVMediaTypeVideo].lastObject;

// Apply the original transform.    
if (assetVideoTrack && compositionVideoTrack) {
   [compositionVideoTrack setPreferredTransform:assetVideoTrack.preferredTransform];
}