AVFoundation Extensions Improvements

Currently, extension methods in TimecodeKit on AVFoundation objects (AVAsset, AVAssetTrack, AVMovie) are somewhat limited as far as reading and writing timecode track information.

1. Improve/Extend Functionality

Multiple timecode events are possible in a single timecode track, especially if a video track contains multiple edits.

The current implementation (as of TimecodeKit 2.0.10) covers the essential functionality of:

[x] reading timecode track(s) and returning the start timecode (startTimecode())
[x] reading all timecode event(s) from all timecode track(s) (timecodes())
[x] writing a timecode track using a single origin timecode (addTimecodeTrack() / replaceTimecodeTrack())

AVAsset Future Feature Roadmap

[ ] writing complex timelines with more than one timecode event
- [ ] add an overload for addTimecodeTrack() and replaceTimecodeTrack() that takes a dictionary of [TimeInterval: Timecode] or something akin to it, keyed by time offsets from movie start with the timecode as values
[ ] refactor methods like timecodes() → [[Timecode]] to include time ranges
[ ] support negative timecode (using negative bit for 32 and 64 bit timecode encoding)
[ ] read/write Adobe Premiere XML data chunk in video file header, which contains timecode information
- Extensible Metadata Platform (Wikipedia)
- Get Timecode from MP4 generated in Adobe Premiere - StackOverflow
[ ] Final Cut Pro embed chunk?
[ ] Avid / Pro Tools embed chunk?

2. Improve `async`/`await` Support

Numerous AVFoundation methods being used by TimecodeKit in order to read/write AVAsset/AVMovie data are using legacy (deprecated) synchronous methods on AVFoundation objects. It would be ideal to add async variants to TimecodeKit methods to use the newer asynchronous counterparts.

[x] Refactor asynchronous completion closure-based methods to async (implemented in TimecodeKit 2.2.0)

orchetect / TimecodeKit