ios - AVAssetExportSession Trim & Download -

i'm trying trim , download online video using avexportsession.

code:

filemove *filemove = (filemove*)data;   nsstring *url = @"http://download.wavetlan.com/svv/media/http/h264/talkinghead_media/h264_test1_talkinghead_mp4_480x360.mp4";     nsurl *videourl = [nsurl urlwithstring:[url stringbyaddingpercentescapesusingencoding:nsutf8stringencoding]];     nslog(@"videourl: %@",videourl);       avasset *anasset = [avurlasset urlassetwithurl:videourl options:nil];         nsarray *compatiblepresets = [avassetexportsession exportpresetscompatiblewithasset:anasset];     if ([compatiblepresets containsobject:avassetexportpresetlowquality]) {         avassetexportsession *exportsession = [[avassetexportsession alloc]                                                initwithasset:anasset presetname:avassetexportpresetlowquality];         nsurl *outputurl = [nsurl fileurlwithpath:filemove.dst];         nslog(@"outputurl: %@",outputurl);         exportsession.outputurl = outputurl;         exportsession.outputfiletype = avfiletypequicktimemovie;          cmtime start = cmtimemakewithseconds(1.0, 600);         cmtime duration = cmtimemakewithseconds(3.0, 600);         cmtimerange range = cmtimerangemake(start, duration);         exportsession.timerange = range;          if ([[nsfilemanager defaultmanager] fileexistsatpath:filemove.dst])             [[nsfilemanager defaultmanager] removeitematpath:filemove.dst error:nil];          [exportsession exportasynchronouslywithcompletionhandler:^{              switch ([exportsession status]) {                 case avassetexportsessionstatusfailed:                     nslog(@"export failed: %@", [[exportsession error]description ]);                     break;                 case avassetexportsessionstatuscancelled:                     nslog(@"export canceled");                     break;                 default:                     break;             }         }];     } 

error:

export failed: error domain=avfoundationerrordomain code=-11800 "the operation not completed" userinfo=0x635a820 {nslocalizeddescription=the operation not completed, nsunderlyingerror=0x1ff4240 "the operation couldn’t completed. (osstatus error -12780.)", nslocalizedfailurereason=an unknown error occurred (-12780)}

do guys see issue in code ? there limitation in avexportsession accessing online video ?

the url used creating avasset needs local file have access to. need download onto device before creating avasset like so