ios - AVAssetExportSession ignoring videoComposition rotation & stripping metadata -

i attempting rotate video prior upload on ios device because other platforms (such android) not interpret rotation information in ios-recorded videos and, result, play them improperly rotated.

i have looked @ following stack posts have not had success apply of them case:

• ios rotate every frame of video

• rotating video w/ avmutablevideocompositionlayerinstruction

• avmutablevideocomposition rotated video captured in portrait mode

• ios avfoundation: setting orientation of video

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i coped apple avsimpleeditor project sample, unfortunately ever happens is, upon creating avassetexportsession , calling exportasynchronouslywithcompletionhandler, no rotation performed, , what's worse, rotation metadata stripped out of resulting file.

here code runs export:

avassetexportsession *exportsession = [[avassetexportsession alloc] initwithasset:[_mutablecomposition copy] presetname:avassetexportpresetpassthrough]; exportsession.outputurl = outputurl; exportsession.outputfiletype = avfiletype3gpp; exportsession.shouldoptimizefornetworkuse = yes; exportsession.videocomposition = _mutablevideocomposition;  [exportsession exportasynchronouslywithcompletionhandler:^(void)  {      nslog(@"status %d %@", exportsession.status, exportsession.error);       handler(exportsession);      [exportsession release];  }]; 

the values _mutablecomposition , _mutablevideocomposition initialized method here:

- (void) getvideocomposition:(avasset*)asset {      avmutablecomposition *mutablecomposition = nil;     avmutablevideocomposition *mutablevideocomposition = nil;      avmutablevideocompositioninstruction *instruction = nil;     avmutablevideocompositionlayerinstruction *layerinstruction = nil;     cgaffinetransform t1;     cgaffinetransform t2;      avassettrack *assetvideotrack = nil;     avassettrack *assetaudiotrack = nil;     // check if asset contains video , audio tracks     if ([[asset trackswithmediatype:avmediatypevideo] count] != 0) {         assetvideotrack = [asset trackswithmediatype:avmediatypevideo][0];     }     if ([[asset trackswithmediatype:avmediatypeaudio] count] != 0) {         assetaudiotrack = [asset trackswithmediatype:avmediatypeaudio][0];     }      cmtime insertionpoint = kcmtimezero;     nserror *error = nil;       // step 1     // create composition given asset , insert audio , video tracks asset     // check whether composition has been created, i.e, other tool has been applied     // create new composition     mutablecomposition = [avmutablecomposition composition];      // insert video , audio tracks avasset     if (assetvideotrack != nil) {         avmutablecompositiontrack *compositionvideotrack = [mutablecomposition addmutabletrackwithmediatype:avmediatypevideo preferredtrackid:kcmpersistenttrackid_invalid];         [compositionvideotrack inserttimerange:cmtimerangemake(kcmtimezero, [asset duration]) oftrack:assetvideotrack attime:insertionpoint error:&error];     }     if (assetaudiotrack != nil) {         avmutablecompositiontrack *compositionaudiotrack = [mutablecomposition addmutabletrackwithmediatype:avmediatypeaudio preferredtrackid:kcmpersistenttrackid_invalid];         [compositionaudiotrack inserttimerange:cmtimerangemake(kcmtimezero, [asset duration]) oftrack:assetaudiotrack attime:insertionpoint error:&error];     }       // step 2     // translate composition compensate movement caused rotation (since rotation cause move out of frame)     t1 = cgaffinetransformmaketranslation(assetvideotrack.naturalsize.height, 0.0);     // rotate transformation     t2 = cgaffinetransformrotate(t1, degreestoradians(90.0));       // step 3     // set appropriate render sizes , rotational transforms     // create new video composition     mutablevideocomposition = [avmutablevideocomposition videocomposition];     mutablevideocomposition.rendersize = cgsizemake(assetvideotrack.naturalsize.height,assetvideotrack.naturalsize.width);     mutablevideocomposition.frameduration = cmtimemake(1, 30);      // rotate transform set on layer instruction     instruction = [avmutablevideocompositioninstruction videocompositioninstruction];     instruction.timerange = cmtimerangemake(kcmtimezero, [mutablecomposition duration]);     layerinstruction = [avmutablevideocompositionlayerinstruction videocompositionlayerinstructionwithassettrack:(mutablecomposition.tracks)[0]];     [layerinstruction settransform:t2 attime:kcmtimezero];       // step 4     // add transform instructions video composition     instruction.layerinstructions = @[layerinstruction];     mutablevideocomposition.instructions = @[instruction];      tt_release_safely(_mutablecomposition);     _mutablecomposition = [mutablecomposition retain];     tt_release_safely(_mutablevideocomposition);     _mutablevideocomposition = [mutablevideocomposition retain]; } 

i pulled method avserotatecommand from here. can suggest why method not rotate video necessary 90 degrees?

because using avassetexportpresetpassthrough avassetexportsession ignore videocomposition, use other preset.