Environment Device: iPhone (reproducible on multiple devices) OS: iOS 27 Beta 1, Beta 2 Video Format: MP4 (H.264 Main Profile) Playback Method: Apple basic player (HTML5 Video / AVPlayer) Issue We are experiencing video stuttering during playback of a specific MP4 file on iOS 27 Beta 1 and Beta 2. The video plays smoothly on previous iOS versions, but on iOS 27 Beta, playback becomes choppy with noticeable frame drops. Steps to Reproduce Prepare a device running iOS 27 Beta 1 or Beta 2. Open the video URL. https://pdst.mimacstudy.com/daesungmimacfree/CDN/MIMAC/PUBLIC/IPS/2026/P260529018_H.mp4 Start playback. Expected Result The video should play smoothly without visible frame drops. Actual Result The video stutters during playback and appears to drop frames intermittently. Additional Information The issue is consistently reproducible. The affected file is encoded as H.264 Main Profile in an MP4 container. No obvious AVPlayer or system error logs are generated during playback. Has anyone observed similar behavior on iOS 27 Beta, or is there any known change in H.264 decoding behavior that could explain this issue?