AVAssetExportSession fails to convert .mov from photo library. Why? - ios

Question

Scenario:
I wish to reduce the size of individual videos from my iTouch photo library.
1. Collect videoAssets from library.
2. Get a thumbnail of the PHAsset - works.
3. Get the actual video from the library.
4. Request the AVAssetForVideo from the library.
5. Convert the video via ExportSessions... loading assorted parameters.
6. Attempt to run the export into a tmp directory for use.
* FAILS *
Here's the debug output:
Here's the error message:
func getVideoFromPhotoLibrary() {
let videoAssets = PHAsset.fetchAssetsWithMediaType(.Video, options:nil)
videoAssets.enumerateObjectsUsingBlock {
(obj:AnyObject!, index:Int, stop:UnsafeMutablePointer<ObjCBool>) in
let mySize = CGSizeMake(120,120)
let myAsset = obj as! PHAsset
let imageManager = PHImageManager.defaultManager()
var myVideo:BlissMedium?
// Request the poster frame or the image of the video
imageManager.requestImageForAsset(myAsset, targetSize:mySize, contentMode: .AspectFit, options: nil) {
(imageResult, info) in
let thumbnail = UIImage(named:"videoRed")
myVideo = BlissMedium(blissImage: imageResult, creationDate:myAsset.creationDate)
myVideo!.mediumType = .video
}
// Actual Video:
imageManager.requestAVAssetForVideo(myAsset, options: nil, resultHandler: {result, audio, info in
let asset = result as! AVURLAsset
let mediaURL = asset.URL
let session = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)
let filename = "composition.mp4"
session.outputURL = NSURL(string: NSTemporaryDirectory());
session.outputFileType = AVFileTypeQuickTimeMovie;
session.exportAsynchronouslyWithCompletionHandler({ () -> Void in
dispatch_async(dispatch_get_main_queue(), {
if session.status == AVAssetExportSessionStatus.Completed {
println("Success")
}
else {
println(session.error?.localizedDescription)
//The requested URL was not found on this server.
}
})
})
})
if nil != myVideo {
self.gBlissVideoMedia.append(myVideo!)
}
}
}
I checked to be sure the target path/file exist; then I added the 'AVFileTypeMPEG4' output type to match the intended .mp4:
let targetDir = createTempDirectory("bliss/composition.mp4") as String?
if NSFileManager.defaultManager().fileExistsAtPath(targetDir!) {
println("*** file exists! ***")
} else {
return
}
session.outputURL = NSURL(string: targetDir!);
session.outputFileType = AVFileTypeMPEG4
I'm still having problems:
* file exists! *
Optional("The operation could not be completed")
What am I doing wrong; what's missing?
Update:
I'm able to successfully run the export to my NSHomeDirectory() vs NSTemporaryDictory() in Objective-C.
However... the same code written in Swift fails.
I notice a change in absolute path to the target output in Swift, not found in Objective-C:
Perhaps it's a Swift 1.2 bug???

Answer 1

I am not sure if you can save in the root of the temp directory, I normally use this function to create a new temp directory that I can use:
func createTempDirectory(myDir: String) -> String? {
let tempDirectoryTemplate = NSTemporaryDirectory().stringByAppendingPathComponent(myDir)
let fileManager = NSFileManager.defaultManager()
var err: NSErrorPointer = nil
if fileManager.createDirectoryAtPath(tempDirectoryTemplate, withIntermediateDirectories: true, attributes: nil, error: err) {
return tempDirectoryTemplate
} else {
return nil
}
}
Try to make your conversion in the directory returned by this function.
I hope that helps you!

Answer 2

I didn't quite understand what that last part of code did, where you find out if a file exists or not. Which file is it you are locating?
Since I didn't understand that then this might be irrelevant, but in your topmost code I notice that you set the filename to composition.mp4, but let the outputURL be NSURL(string: NSTemporaryDirectory()). With my lack of Swiftness I might be missing something, but it seems to me as if you're not using the filename at all, and are trying to write the file as a folder. I believe setting a proper URL might fix the problem but I'm not sure. An Objective-c-example of this could be:
NSURL * outputURL = [[NSURL alloc]
initFileURLWithPath:[NSString pathWithComponents:
#[NSTemporaryDirectory(), #"composition.mp4"]]];
The outputURL is supposed to point to the actual file, not the folder it lies in. I think..
Anyway, if that doesn't work I do have a few other thoughts as well.
Have you tried it on an actual device? There may be a problem with the simulator.
Also, sadly, I have gotten the error -12780 countless times with different root-problems, so that doesn't help very much.
And, I see you check if session.status == AVAssetExportSessionStatus.Completed, have you checked what the actual status is? Is it .Failed, or perhaps .Unknown? There are several statuses.
This might be a long shot, but in one of my apps I am using the camera to capture video/audio, then encode/convert it using AVAssetExportSession. There were strange errors when starting to record, as well as after recording(exporting). I found out that I could change the AVAudioSession, which apparently has something to do with how the device handles media.
I have no idea how to Swift, but here's my code (in viewDidAppear of the relevant view)
NSError *error;
AVAudioSession *aSession = [AVAudioSession sharedInstance];
[aSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error];
[aSession setMode:AVAudioSessionModeVideoRecording error:&error];
[aSession setActive: YES error: &error];
The category PlayAndRecord allowed me to start the camera much faster, as well as getting rid of the occasional hanging AVAssetExportSessionStatus.Unknown and the occasional crash .Failed (which also threw the -12780-error).