[exportSession exportAsynchronouslyWithCompletionHandler: ^(void) {} giving export error? - ios

Question

I have made a sample app to trim a video by getting it from camera roll. Written code is as follows:
-(IBAction)cutVideo
{
NSString *path=[NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) objectAtIndex:0];
path=[path stringByAppendingPathComponent:#"new.mov"];
[self splitVideo:path];
}
- (void)splitVideo:(NSString *)outputURL
{
#try
{
NSURL *fileURL=[[NSURL alloc] init];
fileURL=[NSURL fileURLWithPath:outputURL];
fileURL=[NSURL URLWithString:outputURL];
// NSString *videoBundleURL = [[NSBundle mainBundle] pathForResource:#"samp" ofType:#"mov"];
AVAsset *asset = [[AVURLAsset alloc] initWithURL:fileURL options:nil];
NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:asset];
if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality])
{
[self trimVideo:outputURL assetObject:asset];
}
// videoBundleURL = nil;
asset = nil;
compatiblePresets = nil;
}
#catch (NSException * e)
{
NSLog(#"Exception Name:%# Reason:%#",[e name],[e reason]);
}
}
- (void)trimVideo:(NSString *)outputURL assetObject:(AVAsset *)asset
{
#try
{
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
exportSession.outputURL = [NSURL fileURLWithPath:outputURL];
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
CMTime start = CMTimeMakeWithSeconds(startTime, 1);
CMTime duration = CMTimeMakeWithSeconds((endTime - startTime), 1);
CMTimeRange range = CMTimeRangeMake(start, duration);
exportSession.timeRange = range;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
if ([[NSFileManager defaultManager] fileExistsAtPath:outputURL])
{
[[NSFileManager defaultManager] removeItemAtPath:outputURL error:nil];
}
[exportSession exportAsynchronouslyWithCompletionHandler: ^(void) {
NSLog(#"Export Status %d %#", exportSession.status, [exportSession.error description]);
}];
exportSession = nil;
}
#catch (NSException * e)
{
NSLog(#"Exception Name:%# Reason:%#",[e name],[e reason]);
}
}
all is working fine but error is in export file .. error is as follows
2012-12-12 13:27:27.896 RecordVideo[1472:907] Export Status 4 Error
Domain=NSURLErrorDomain Code=-1 "unknown error" UserInfo=0x1e577ad0
{NSErrorFailingURLStringKey=/var/mobile/Applications/A38CC8B9-A8CB-4A65-8308-
24A9BEB27626/Library/Documentation/new.mov,
NSErrorFailingURLKey=/var/mobile/Applications/A38CC8B9-A8CB-4A65-8308-
24A9BEB27626/Library/Documentation/new.mov, NSLocalizedDescription=unknown error,
NSUnderlyingError=0x1e537da0 "The operation couldn’t be completed. (OSStatus error
-12935.)", NSURL=/var/mobile/Applications/A38CC8B9-A8CB-4A65-8308-
24A9BEB27626/Library/Documentation/new.mov}
Any help will be appreciated, thanks