Generating Video Thumbnails with AVAssetImageGenerator
WHAT IT TESTS: AVFoundation usage plus async UI hygiene. OUTLINE: load AVAsset, configure AVAssetImageGenerator, request the time off the main thread, hop back to update UI. RED FLAG: doing the decode synchronously on the main thread.
WHAT IT TESTS: practical AVFoundation knowledge and threading discipline. ANSWER OUTLINE: create an AVAsset for the URL, build an AVAssetImageGenerator, set appliesPreferredTrackTransform true so orientation is correct, and call the async copyCGImage API for a CMTime. Set maximumSize to avoid decoding a full-resolution frame, use a tolerance to let it snap to a nearby keyframe for speed, never block the main thread, and dispatch the resulting UIImage back to the main queue. RED FLAG: synchronous decoding on the main thread, freezing scrolling.
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- #ios
- #swift
- #avfoundation
- #concurrency
- #performance
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