ios - Monotouch, Trimming Video Fails -

i trying trim video 5 seconds programmatically. here 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 , 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 trimmed", null, "o k").show ();             });         }         else          {             invokeonmainthread (() => {                 new uialertview ("export falure", exportsession.error.description, null, "o k").show ();             });         } } 

but in completion getting filed status. full nserror description follows

error domain=avfoundationerrordomain code=-11800 "the operation not completed" userinfo=0x7cebcf80 {nslocalizeddescription=the operation not completed, nsunderlyingerror=0x7cb08410 "the operation couldn’t completed. (osstatus error -12105.)", nslocalizedfailurereason=an unknown error occurred (-12105)} 

what possibly doing wrong ?

edit: have referred apple's doumentation on trimming video , have modified above code no positive effect 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 , 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); 

try code below. modified exportsession.outputurl , how initialize cmtimerange. trimming down 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 , 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);