Questions regarding how rotated videos are stored in recent iOS versions

ChatGPT & Gemini says:

🎥 What iOS 5 Introduced:

• AVFoundation's AVCaptureVideoDataOutput in iOS 5 allowed apps to rotate video buffers during capture (i.e., physical rotation of raw video data).
• But this applied only to developer-controlled camera capture sessions, not to videos recorded using the native Camera app.

So technically, yes — physical rotation became possible in iOS 5, but only if a developer explicitly implemented it in a custom camera app.

📱 What Changed Around iOS 13+:

Starting in iOS 13, there is growing evidence (based on video behavior, file metadata, and developer observations) that:

• The built-in Camera app began physically rotating the video frames before encoding (or as part of it), rather than relying solely on rotation metadata.
• This was likely done to improve playback consistency across platforms (especially web browsers, many of which ignore rotation metadata).

In short:

iOS Version Rotation Handling in Videos

• iOS ≤12Fixed orientation + metadata (typical "landscape but rotate with tag")
• iOS 13+Native Camera app started rotating video content before encoding (metadata = 0°)

✅ Summary:

You're likely seeing the effects of a shift in default behavior for the built-in Camera app starting with iOS 13, even though developer-level support for physical rotation has existed since iOS 5.

Best Practice: Use physical rotation during capture when necessary, but be mindful of performance implications. Alternatively, apply transforms post-capture to achieve the desired orientation.​