FLV videos don't work properly with VideoTexture in iOS (only audio is played)

I'm trying to use the new VideoTexture functionality, but I've found that while FLV videos do play properly in ADL (in both MacOS and Windows), they don't when debugging in iOS (audio can be heard but video is black),

Are only MP4 videos supported when using VideoTexture in iOS? Are FLVs out of the question for that kind of usage?

I'm using AIR 18 SDK.

Thank you!