AVAssetExportSession rotation error's when video is from camera roll

Question

I am trying to convert .mov video to .mp4 and at the same time correcting the orientation. The code I use below works great when recording a video using `UIImagePickerController` however if the video is selected from the camera roll I get this error and I don't see why: Export failed: Operation Stopped : Error Domain=AVFoundationErrorDomain Code=-11841 "Operation Stopped" UserInfo=0x1815ca50 {NSLocalizedDescription=Operation Stopped, NSLocalizedFailureReason=The video could not be composed.} I have tried first saving the video to another file, but it made no difference. Here is the code I am using to convert the video: ``` - (void)convertVideoToLowQuailtyAndFixRotationWithInputURL:(NSURL*)inputURL handler:(void (^)(NSURL *outURL))handler { if ([[inputURL pathExtension] isEqualToString:@"MOV"]) { NSURL *outputURL = [inputURL URLByDeletingPathExtension]; outputURL = [outputURL URLByAppendingPathExtension:@"mp4"]; AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:inputURL options:nil]; A…

Accepted Answer

AVFoundation Error Constant -11841 means that you have an invalid video composition. See this link if you'd like more info on the error constants: https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVFoundation_ErrorConstants/Reference/reference.html

While no major errors pop out at me immediately, I can suggest the following ways to narrow down the source of your problem.

First, instead of passing `nil` for the `error` parameter in these calls:

```
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, avAsset.duration)
                                       ofTrack:sourceVideoTrack
                                        atTime:kCMTimeZero error:nil];
```

create an `NSError` object and pass the reference to it like so:

```
NSError *error = nil;
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, avAsset.duration)
                                       ofTrack:sourceVideoTrack
                                        atTime:kCMTimeZero error:&error];
```

Examine the error to make sure your video and audio tracks get inserted in the composition track correctly. The error should be `nil` if all goes well.

```
if(error)
    NSLog(@"Insertion error: %@", error);
```

You may also want to check your AVAsset's `composable` and `exportable`, and `hasProtectedContent` properties. If these are not YES, YES, and NO, respectively, you may have a problem creating your new video file.

Occasionally I've seen an issue where creating a time range for an audio track does not like the 600 timescale when used in a composition with a video track. You may want to create a new CMTime for the duration (avAsset.duration) in

```
CMTimeRangeMake(kCMTimeZero, avAsset.duration) 
```

only for inserting the audio track. In the new CMTime,use a timescale of 44100 (or whatever the sample rate of the audio track is.) The same goes for your `videoComposition.frameDuration`. Depending on the `nominalFrameRate` of your video track, your time may not be represented correctly with 600 timescale.

Finally, there's a helpful tool provided by Apple to debug video compositions:

https://developer.apple.com/library/mac/samplecode/AVCompositionDebugViewer/Introduction/Intro.html

It gives a visual representation of your composition and you can see where things don't look like they should.

AVAssetExportSession rotation error's when video is from camera roll

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