iOS AVFoundation: Setting Orientation of Video

Question

I've been struggling with several dimensions to the problem of controlling video orientation during and after capture on an iOS device. Thanks to previous answers and documentation from Apple I've been able to figure it out. However, now that I want to push some video to a web site, I'm running into particular problems. I've outlined this problem in particular in this question, and the proposed solution turns out to require orientation options to be set during video encoding.

That may be, but I have no clue how to go about doing this. The documentation around setting orientation is in respect to setting it correctly for display on the device, and I've implemented the advice found here. However, this advice does not address setting the orientation properly for non-Apple software, such as VLC or the Chrome browser.

Can anyone provide insight into how to set orientation properly on the device such that it displays correctly for all viewing software?

Answer 1

Finally,based on the answers of @Aaron Vegh and @Prince, I figured out my resolution: //Converting video

+(void)convertMOVToMp4:(NSString *)movFilePath completion:(void (^)(NSString *mp4FilePath))block{


AVURLAsset * videoAsset = [[AVURLAsset alloc]initWithURL:[NSURL fileURLWithPath:movFilePath]  options:nil];

AVAssetTrack *sourceAudioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

AVMutableComposition* composition = [AVMutableComposition composition];


AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                            preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                               ofTrack:sourceAudioTrack
                                atTime:kCMTimeZero error:nil];




AVAssetExportSession * assetExport = [[AVAssetExportSession alloc] initWithAsset:composition
                                                                      presetName:AVAssetExportPresetMediumQuality];


NSString *exportPath =  [movFilePath stringByReplacingOccurrencesOfString:@".MOV" withString:@".mp4"];


NSURL * exportUrl = [NSURL fileURLWithPath:exportPath];


assetExport.outputFileType = AVFileTypeMPEG4;
assetExport.outputURL = exportUrl;
assetExport.shouldOptimizeForNetworkUse = YES;
assetExport.videoComposition = [self getVideoComposition:videoAsset composition:composition];

[assetExport exportAsynchronouslyWithCompletionHandler:
 ^(void ) {
     switch (assetExport.status)
     {
         case AVAssetExportSessionStatusCompleted:
             //                export complete
                    if (block) {
                         block(exportPath);
                }
             break;
         case AVAssetExportSessionStatusFailed:
             block(nil);
             break;
         case AVAssetExportSessionStatusCancelled:
            block(nil);
             break;
     }
 }];
}

//get current orientation

  +(AVMutableVideoComposition *) getVideoComposition:(AVAsset *)asset composition:( AVMutableComposition*)composition{
    BOOL isPortrait_ = [self isVideoPortrait:asset];


    AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];


    AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:videoTrack atTime:kCMTimeZero error:nil];

    AVMutableVideoCompositionLayerInstruction *layerInst = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];

    CGAffineTransform transform = videoTrack.preferredTransform;
    [layerInst setTransform:transform atTime:kCMTimeZero];


    AVMutableVideoCompositionInstruction *inst = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    inst.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
    inst.layerInstructions = [NSArray arrayWithObject:layerInst];


    AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
    videoComposition.instructions = [NSArray arrayWithObject:inst];

    CGSize videoSize = videoTrack.naturalSize;
    if(isPortrait_) {
        NSLog(@"video is portrait ");
        videoSize = CGSizeMake(videoSize.height, videoSize.width);
    }
    videoComposition.renderSize = videoSize;
    videoComposition.frameDuration = CMTimeMake(1,30);
    videoComposition.renderScale = 1.0;
    return videoComposition;
   }

//get video

+(BOOL) isVideoPortrait:(AVAsset *)asset{
BOOL isPortrait = FALSE;
NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
if([tracks    count] > 0) {
    AVAssetTrack *videoTrack = [tracks objectAtIndex:0];

    CGAffineTransform t = videoTrack.preferredTransform;
    // Portrait
    if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0)
    {
        isPortrait = YES;
    }
    // PortraitUpsideDown
    if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0)  {

        isPortrait = YES;
    }
    // LandscapeRight
    if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0)
    {
        isPortrait = FALSE;
    }
    // LandscapeLeft
    if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0)
    {
        isPortrait = FALSE;
    }
}
return isPortrait;

}