Browse through AVFoundation / AVKit APIs

[defagos]

As a developer I need to know which tools are available natively from the player I use. Those have been extended in recent years and some might be extremely handy in implementing features we desire.

Acceptance criteria

• AVFoundation APIs have been covered.
• AVKit APIs have been covered.

Tasks

• Read AVFoundation framework headers.
• Read AVKit framework headers.
• Read AVFoundation documentation.
• Read AVKit documentation.
• Link useful documentation in our wiki.
• Produce a list of which APIs could be investigated / used for some features. Also see comments written in the Letterbox PoC issue.

[defagos]

AVPlayer APIs

Some old and new APIs which might be useful someday:

• setRate(_ rate:time:atHostTime:): Could this be helpful for setting a relationship between stream time and clock time in DVR streams?
• preroll(atRate:) for faster startup in some cases?
• automaticallyWaitsToMinimizeStalling, though how this flag is set should also take into account whether a resource loader is attached to the asset and what it does (see associated documentation).
• timeControlStatus and reasonForWaitingToPlay.
• rate, defaultRate and play() / playImmediately(atRate:).

AVPlayerItem APIs

• configuredTimeOffsetFromLive, recommendedTimeOffsetFromLive and automaticallyPreservesTimeOffsetFromLive to fine-tune behavior when playing livestreams. See corresponding WWDC 19 talk.
• forwardPlaybackEndTime and reversePlaybackEndTime: Could these be useful to implement behavior at content edges with |rate| > 1, e.g. when approaching the live edge at high playback rates?
• timebase: Could it be useful to learn about the relationship between stream time and clock time?
• step(byCount:): For skip forward / backward?
• canUseNetworkResourcesForLiveStreamingWhilePaused: Could it be used to reduce network usage when playing DVR streams without negatively impacting the user experience?
• preferredForwardBufferDuration (could be helpful to prevent livestream buffering).

AVAsset APIs

• minimumTimeOffsetFromLive: Can probably be used to guess the DVR live edge size from the asset itself.
• ...

[defagos]

Guess that's enough for now. We readily use a number of new APIs (control center, async loading, live offset preservation, etc.) and can keep the above list as reference.