Trimming video with Monotouch fails with "The operation could not be completed" - ios

Question

I am trying to trim a video to 5 seconds programmatically. Here is my implementation.
AVAssetExportSession exportSession= new AVAssetExportSession(videoAsset,AVAssetExportSession.PresetLowQuality.ToString());
int SystemVersion = Convert.ToInt16(UIDevice.CurrentDevice.SystemVersion.Split('.')[0]);
string filename;
if (SystemVersion >= 8)
{
var documents = NSFileManager.DefaultManager.GetUrls(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomain.User)[0].Path;
filename = Path.Combine(documents, "trimmed.mov");
}
else
{
var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); // iOS 7 and earlier
filename = Path.Combine(documents, "trimmed.mov");
}
outputUrl=new NSUrl(filename);
exportSession.OutputUrl = outputUrl;
CMTime start = new CMTime((long)1, 1);
CMTime duration = new CMTime((long)5, 1);
CMTimeRange range = new CMTimeRange();
range.Start=start;
range.Duration=duration;
exportSession.TimeRange = range;
exportSession.OutputFileType = AVFileType.QuickTimeMovie;
ExportTrimmedVideo( exportSession);
async void ExportTrimmedVideo(AVAssetExportSession exportSession)
{
await exportSession.ExportTaskAsync ();
if (exportSession.Status == AVAssetExportSessionStatus.Completed) {
InvokeOnMainThread (() => {
new UIAlertView ("Export Sucess", "Video is trimmed", null, "O K").Show ();
});
}
else
{
InvokeOnMainThread (() => {
new UIAlertView ("Export Falure", exportSession.Error.Description, null, "O K").Show ();
});
}
}
But in completion I am getting a Filed Status. Full NSError Description is as follows
Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo=0x7cebcf80 {NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x7cb08410 "The operation couldn’t be completed. (OSStatus error -12105.)", NSLocalizedFailureReason=An unknown error occurred (-12105)}
What am I possibly doing wrong ?
Edit
I have referred apple's documentation on Trimming video and have modified the above code with no positive effect as below.
var compatiblePresets= AVAssetExportSession.ExportPresetsCompatibleWithAsset(videoAsset).ToList();
var preset="";
if(compatiblePresets.Contains("AVAssetExportPresetLowQuality"))
{
preset="AVAssetExportPresetLowQuality";
}
else
{
preset=compatiblePresets.FirstOrDefault();
}
AVAssetExportSession exportSession= new AVAssetExportSession(videoAsset,preset);
int SystemVersion = Convert.ToInt16(UIDevice.CurrentDevice.SystemVersion.Split('.')[0]);
string filename;
if (SystemVersion >= 8)
{
var documents = NSFileManager.DefaultManager.GetUrls(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomain.User)[0].Path;
filename = Path.Combine(documents, "trimmed.mov");
}
else
{
var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); // iOS 7 and earlier
filename = Path.Combine(documents, "trimmed.mov");
}
outputUrl=new NSUrl(filename);
exportSession.OutputUrl = outputUrl;
exportSession.OutputFileType = AVFileType.QuickTimeMovie;
CMTime start = new CMTime((long)1, 600);
CMTime duration = new CMTime((long)5, 600);
CMTimeRange range = new CMTimeRange();
range.Start=start;
range.Duration=duration;
exportSession.TimeRange = range;
ExportTrimmedVideo( exportSession);

Answer 1

Try this code below. I modified exportSession.OutputUrl and how you initialize your CMTimeRange. Are you trimming it down to a 4 second clip?
var compatiblePresets= AVAssetExportSession.ExportPresetsCompatibleWithAsset(videoAsset).ToList();
var preset="";
if(compatiblePresets.Contains("AVAssetExportPresetLowQuality"))
{
preset="AVAssetExportPresetLowQuality";
}
else
{
preset=compatiblePresets.FirstOrDefault();
}
using (var exportSession = new AVAssetExportSession(videoAsset, preset))
{
int SystemVersion = Convert.ToInt16(UIDevice.CurrentDevice.SystemVersion.Split('.')[0]);
string filename;
if (SystemVersion >= 8)
{
var documents = NSFileManager.DefaultManager.GetUrls(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomain.User)[0].Path;
filename = Path.Combine(documents, "trimmed.mov");
}
else
{
var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); // iOS 7 and earlier
filename = Path.Combine(documents, "trimmed.mov");
}
exportSession.OutputUrl = NSUrl.FromFilename(filename);
exportSession.OutputFileType = AVFileType.QuickTimeMovie;
var range = new CMTimeRange();
range.Start = CMTime.FromSeconds (1, videoAsset.Duration.TimeScale);
range.Duration = CMTime.FromSeconds (5, videoAsset.Duration.TimeScale);
exportSession.TimeRange = range;
}
ExportTrimmedVideo( exportSession);