We support any format that is natively supported. Information for different platforms can be found on the following pages:
Overall, using .mp4 is recommended, as it can be used across all platforms and provides very good compression.
HD videos are fully supported. AR is rendered at 30fps so exceeding this framerate has no benefit. Framerates as low as 24fps are often imperceptible and can result in a much smaller video file size.
Alpha videos are videos with a transparency channel. These are especially useful in AR where it is desirable to have the camera background behind.
The video must be chroma keyed in software such as AfterEffects and exported as a series of transparent PNGs. The SDK provides a tool for converting these to a video.
Videos have a jitter threshold that can be set which causes the audio to continue playing across momentary losses of tracking.
Yes, the ARFullScreenManager has been implemented in the iOS SDK.
As of Unity 5.6, the engine has a new video playback API, which can be used to play videos on mobile devices. Kudan's Unity Plugin V2.0 takes full advantage of this new API.