I want to add some info (metadata) to a video. I have found a way to retrieve metadata, but did not find any solution to set or modify metadata. I am using AVURLAsset, AVAssetWritter also AVMutableComposition for creating the video.
Use -[AVAssetWriter setMetadata:].
This is set to an NSArray of AVMutableMetadataItems. Note that you cannot set the value after writing has started.
Metadata keys and keyspaces are listed in AVMetadataFormat.h.
When using AVMutableComposition, you can set the metadata property on the AVAssetExportSession when you go to write it out, rather than setting it on the asset (the composition) itself.
If you need to do it "off line". I've used the id3taggenerator and related tools and they work great.
Checkout more info here: http://developer.apple.com/library/mac/#documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/UsingHTTPLiveStreaming/UsingHTTPLiveStreaming.html
Or here's a tutorial I used for adding timed metadata that's pretty good: http://jmacmullin.wordpress.com/2010/11/03/adding-meta-data-to-video-in-ios/
If you want to add meta data in-app (as in a user records a video and add's their own meta data) I'm not sure there.
Check out gusutils ==>
https://github.com/gpambrozio/GusUtils
There is an xcode project for creating a static library that lets you add metadata and geolocation information to your video and then persist to the assets library.
来源：https://stackoverflow.com/questions/10480991/add-custom-metadata-to-video-using-avfoundation