Add metadata to .mov

Question

Created Dec ’15

Replies 7

Boosts 0

Views 1.3k

Participants 3

I tried to translate the code of AVTimedAnnotationWriter from Objective-C to Swfit. Everything works but when I'm writing the metadata part, it fails.

I noticed that when the mediaType = "meta" (line13). It will occur one more copyNextTimedMetadataGroup(). Any idea?

func startReadingAndWritingWithCompletionHandler(localCompletionHandler: dispatch_block_t) {
        self.completionHandler = localCompletionHandler
  
        assetWriterInput?.requestMediaDataWhenReadyOnQueue(serializationQueue!, usingBlock: { () -> Void in
            if(self.finished!) {
                return
            }
            var completedOrFailed: Bool = false
            /
            while ((self.assetWriterInput?.readyForMoreMediaData)! && !completedOrFailed) {
                var sampleBuffer: CMSampleBufferRef? = nil
                var metadataGroup: AVTimedMetadataGroup? = nil
                if((self.assetWriterInput?.mediaType)! == "meta") {
                    metadataGroup = self.metadataSampleProvider?.copyNextTimedMetadataGroup()
                }
                else {
                    sampleBuffer = self.sampleProvider!.copyNextSampleBuffer()
                }
          
                if (sampleBuffer != nil) {
                    let success: Bool = (self.assetWriterInput?.appendSampleBuffer(sampleBuffer!))!
                    sampleBuffer = nil
                }
                else if (metadataGroup != nil) {
                    let success: Bool = (self.assetWriterAdaptor?.appendTimedMetadataGroup(metadataGroup!))!
                    completedOrFailed = !success
                }
                else {
                    completedOrFailed = true
                }
          
            }
      
            if(completedOrFailed) {
                self.callCompletionHandlerIfNecessary()
            }
      
        })
    }

My AVTimedMetadataGroup count is exactly 181. But the copyNextTimedMetadataGroup() will run 182 times. In other words, the last try will return nil. (Error)

func copyNextTimedMetadataGroup() -> AVTimedMetadataGroup {
        var group: AVTimedMetadataGroup?
        // self.currentSampleNum = 0 ; self.numOfSamples = 181
        if (self.currentSampleNum < self.numOfSamples)
        {
            group = self.metadataSamples[currentSampleNum] as! AVTimedMetadataGroup
            self.currentSampleNum++
        }
        return group!
    }

Boost

Answer 1

jeschot OP

Dec ’15

It runs one more time because that's when completedOrFailed is set to true because of completion.

The fix is simple:

func copyNextTimedMetadataGroup() -> AVTimedMetadataGroup? {
var group: AVTimedMetadataGroup?
if (self.currentSampleNum < self.numOfSamples) 
{
group = self.metadataSamples[currentSampleNum] as! AVTimedMetadataGroup
self.currentSampleNum++
}
return group
}

BTW you can make your code a little more compact, like so:

var completedOrFailed = false           // Bool type is inferred
var sampleBuffer: CMSampleBufferRef?      // nil is default value

Jan E

0

Answer 2

WJ_tw OP

Dec ’15

Thanks. It works.

However, I tried to get metadata out from my exported file, I got an empty metadata. why?

func playVideo(url: NSURL)
{
     let asset = AVURLAsset(URL: url)
     print(asset.metadata)
}

[] // My console line print out no metadata

0

Answer 3

jeschot OP

Dec ’15

asset.metadata are the "global" metadata. You are creating a timed metadata track.

Try printing asset.tracks

Jan E.

0

Answer 4

jeschot OP

Dec ’15

I am out of ideas.

You can copy the metadata with

writer.metadata = sourceAsset.metadata

I ran the AVTimedAnnotationWriter project on my iPad and it worked OK.

I would like to save the movie to the Photos album instead of the temporary directory. Can you tell how to do that?

Jan E.

0

Answer 5

WJ_tw OP

Dec ’15

Try this

// The temporary path for the video before saving it to the photo album
self.destinationAssetURL = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@%@", NSTemporaryDirectory(), @"Movie.MOV"]];

0

Answer 6

jeschot OP

Dec ’15

That is the code for saving to the temporary folder.

I want to replace that by the photos directory or whatever it is called on iOS (I am a Mac programmer).

Jan E.

0

Answer 7

guywithmazda OP

Dec ’15

You can use UISaveVideoAtPathToSavedVideosAlbum to save the video to the Camera Roll album (devices with camera) or Saved Photos album (devices without camera).

0