在AVMutableComposition中的多个视频轨道之间切换

Question

Is there a way to switch between multiple video tracks in an AVMutableComposition ? I want to assign a different preferredTransform to each, and switch between them.

I tried it by assigning alternating assets to an A track and a B track, but no video showed for the B track time.

Answer 1

It looks like to perform the switching between multiple video tracks ("video downmixing") you need to use AVAssetWriter . According to the docs the class has "automatic interleaving of media data for multiple concurrent tracks".

So, if you want to preview a composition using multiple video tracks, you either need to write it out using AVAssetWriter or compose it in an AVMutableComposition using a single video track only.