AVAssetExport fails for some files - ios

Question

I have tried to export audio file from the iPod-Library. My objective is to create new file in app Document folder with this iPod-Library file .Its fails to create files for some items only . Below is my code snippet.
AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL: url options:nil];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
AVAssetExportSession *exporter = [[AVAssetExportSession alloc]
initWithAsset: songAsset
presetName: AVAssetExportPresetAppleM4A];
exporter.outputFileType = #"com.apple.m4a-audio";
NSString *songName = [filename stringByAppendingString:#".m4a"];
NSString *musicfilepath = [documentsDirectory stringByAppendingPathComponent:#"musics/"];
[[NSFileManager defaultManager] createDirectoryAtPath:musicfilepath withIntermediateDirectories:YES attributes:nil error:nil];
NSString *exportFile = [musicfilepath stringByAppendingPathComponent:songName];
NSError *error1;
if([[NSFileManager defaultManager] fileExistsAtPath:exportFile])
{
[[NSFileManager defaultManager] removeItemAtPath:exportFile error:&error1];
}
NSURL* exportURL = [[NSURL fileURLWithPath:exportFile] retain];
exporter.outputURL = exportURL;
Am getting Error as shown below when tried with the error handler block :
[exporter exportAsynchronouslyWithCompletionHandler:^{
int exportStatus = exporter.status;
switch (exportStatus) {
case AVAssetExportSessionStatusFailed: {
NSError *exportError = exporter.error;
NSLog (#"AVAssetExportSessionStatusFailed: %#", exportError);
break;
}
}
}];
AVAssetExportSessionStatusFailed: Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo=0x214f20 {NSLocalizedFailureReason=An unknown error occurred (-12124), NSUnderlyingError=0x218270 "The operation couldn’t be completed. (OSStatus error -12124.)", NSLocalizedDescription=The operation could not be completed}

Answer 1

Having played a lot with this myself, some of the answers may be relevant and correct. One other thing to watch out for is that I often used to get similar AVFoundation errors if trying to combine videos that had different frame-rates. Check the source files frame rate and check your CMTime's too. You may have to pre-process some files before adding them into a AVMutableComposition.

Answer 2

If you have iTunes match on and the file is not downloaded to the device, this can happen. Can you check to see if that is the case for you? If so I can give code to detect it.
+ (BOOL)isDownloadedFromiCloud:(MPMediaItem *)item {
if ([item valueForProperty:MPMediaItemPropertyAssetURL] != nil) {
AVURLAsset *asset = [AVURLAsset assetWithURL:[item valueForProperty:MPMediaItemPropertyAssetURL]];
if (asset.exportable)
return YES;
}
return NO;
}

Answer 3

I've experienced this too. Are you using iTunes match? It may be that the file is not on the actual device. You can check this on the AVAsset by checking the properties such as hasProtectedContent or ensuring exportable is YES.
Also, I notice you are using the AVExportSession preset AVAssetExportPresetAppleM4A'. This will re-encode the file you are exporting. It may be easier (and much faster) to just pass-though instead usingAVAssetExportPresetPassthrough`. This assumes you are happy with the existing file format, which maybe .m4a, .mp3, .wav etc...

Answer 4

The the music file path your are using might be wrong. Try this
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
documentsDirectory = [documentsDirectory stringByAppendingPathComponent:#"Music"];
NSError* error;
if (![[NSFileManager defaultManager] fileExistsAtPath:documentsDirectory])
[[NSFileManager defaultManager] createDirectoryAtPath:documentsDirectory withIntermediateDirectories:NO attributes:nil error:&error];
NSString *exportFile = [documentsDirectory stringByAppendingPathComponent:songName];
if([[NSFileManager defaultManager] fileExistsAtPath:exportFile])
{
[[NSFileManager defaultManager] removeItemAtPath:exportFile error:&error1];
}
if (error != nil) {
NSURL* exportURL = [[NSURL fileURLWithPath:exportFile] retain];
exporter.outputURL = exportURL;
[exporter exportAsynchronouslyWithCompletionHandler:^{
int exportStatus = exporter.status;
switch (exportStatus) {
case AVAssetExportSessionStatusFailed: {
NSError *exportError = exporter.error;
NSLog (#"AVAssetExportSessionStatusFailed: %#", exportError);
break;
}
}
}
];
}