[Timo972]

Fixes DRO-3359.

Problem

On WDA-controlled phones (iOS < 27), rotating to landscape flips the stream to 1278×588, so the viewer rotates its frame. The picture inside stays un-rotated: a narrow portrait strip with the UI drawn sideways, in Chrome and Safari.

ReplayKit always hands the broadcast extension a portrait buffer and carries the orientation only in RPVideoSampleOrientationKey. Since #33 (e0d899d1), the pipeline swaps the encoder size on rotation, but VTPixelTransferSessionTransferImage only letterboxes the portrait buffer into the new landscape size and never rotates it.

Change

• FBBroadcastFrameRotation maps the orientation tag to the turn that makes the buffer upright: 3 → 180°, 6 → 90° counter-clockwise, 8 → 90° clockwise. Unknown and mirrored values (which ReplayKit doesn't emit) map to no rotation.
• FBExtSessionPipeline handles rotated frames in two steps, because iOS has no rotating pixel transfer (kVTPixelTransferPropertyKey_Rotation is macOS-only) and VTPixelRotationSession can't scale:
  1. scale the frame (letterboxed, as before) into an encoder-sized buffer in the un-rotated orientation;
  2. rotate that buffer into the encoder's buffer.
• The rotation session and the extra buffer pool are created on the first rotated frame and released with the other scaler resources. Each intermediate buffer is encoder-sized (about 1 MB in NV12), well inside the extension's memory cap.
• Upright frames take the existing path unchanged. The direct-source shortcut is skipped while a rotation is needed, so an upside-down frame (same size as portrait) is not encoded un-rotated.
• Rotation needs iOS 16; iOS 15 keeps the previous behaviour.

The quarter-turn mapping is the opposite of what the CGImagePropertyOrientation docs suggest. I first implemented it per the docs, and both landscape directions came out upside down on hardware; the code comment records the measured mapping.

Verification

• Unit tests: UnitTests 255 passed, 1 skipped, including two new tests for FBBroadcastFrameRotation.
• Hardware: iPhone 15 Pro, iOS 26.6.1 ("iPhone 4" on the BYOD host). I built the runner the way Scripts/ci/build-real.sh does, then signed and installed it with mobilerun-ios setup --reinstall. A probe brought the broadcast up (state connected), opened the portal's H.265 capture (50%, 60 fps) with Safari in front, and stepped portrait → landscapeLeft → portrait → landscapeRight → portrait through CoreDevice changeOrientation. For each step I decoded a frame with ffmpeg:
  • landscapeLeft and landscapeRight: 1278×588, upright, filling the frame (before the fix: a sideways portrait strip; with the docs mapping: upside down);
  • each return to portrait: 588×1278, upright, with no reconnect.
• Not covered: the 180° case (orientation 3). Safari doesn't rotate upside-down on an iPhone.

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