fix(render): detect portrait sources that carry rotation metadata

[chekazoid]

Problem

is_portrait_source() compares the dimensions ffprobe reports for the stored stream. Phone cameras record vertical footage as a landscape stream plus a rotation entry in the display matrix. ffmpeg auto-rotates on decode, so the filter graph receives a portrait frame while is_portrait_source() reports landscape — and scale=1920:-2 gets applied to a portrait frame.

Real phone clip (Android, 4:55, shot vertically):

$ ffprobe -v error -select_streams v:0 \
    -show_entries stream=width,height:stream_side_data=rotation ...
width=1280
height=720
rotation=-90        # displayed as 720x1280

extract_segment() on that file, before this change:

1920x3414

A 720p vertical clip upscaled to 3414px tall, on the CPU-bound libx264 path.

#29 fixed sources whose stream is stored portrait (h > w). Sources rotated by metadata — which is how essentially all phone footage is stored — still fall through to the landscape branch. #64 lists portrait orientation as already handled, which is true only for the stored-portrait case.

Fix

Probe the rotation side data (falling back to the rotate stream tag for ffmpeg < 5) and swap width/height when rotation is an odd multiple of 90°. No new dependencies; json was already imported.

Verification

is_portrait_source() across every orientation case:

source	expected	result
1280x720, no rotation	landscape	✅
720x1280, stored portrait (#29)	portrait	✅
1280x720 + rotation 90	portrait	✅
1280x720 + rotation -90	portrait	✅
1280x720 + rotation 180	landscape	✅
real phone clip (1280x720 + rotation -90)	portrait	✅
unreadable path	False fallback	✅

End-to-end through extract_segment() on the real phone clip: 1920x3414 → 720x1280.

Rotation-180 sources stay landscape, and the existing except fallback is unchanged.

Note

This touches the same function as the open #104 (--vertical output). Happy to rebase if that lands first.

---

Summary by cubic

Fix portrait detection for videos that store rotation metadata. is_portrait_source() now reads display rotation so vertical phone clips scale on the correct axis.

• Bug Fixes
  • Parse rotation from ffprobe JSON (side_data.rotation, fallback to tags.rotate) and swap width/height for odd 90° rotations.
  • Keep 180° rotation and error fallback unchanged; prevents 1920x3414 mis-scaling and outputs 720x1280 for rotated 720p clips.

^{Written for commit f38ba27. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="helpers/render.py">

<violation number="1" location="helpers/render.py:160">
P2: Non-right-angle rotation metadata is classified as portrait, so slightly rotated landscape sources can take the portrait scaling path. Limit the swap to 90°/270° rotations, which are the only cases that exchange axes.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Non-right-angle rotation metadata is classified as portrait, so slightly rotated landscape sources can take the portrait scaling path. Limit the swap to 90°/270° rotations, which are the only cases that exchange axes.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At helpers/render.py, line 160:

<comment>Non-right-angle rotation metadata is classified as portrait, so slightly rotated landscape sources can take the portrait scaling path. Limit the swap to 90°/270° rotations, which are the only cases that exchange axes.</comment>

<file context>
@@ -132,15 +132,33 @@ def is_hdr_source(video: Path) -> bool:
+            # ffmpeg < 5 exposes the display matrix as a stream tag instead.
+            rotation = int(stream.get("tags", {}).get("rotate", 0))
+
+        if rotation % 180 != 0:
+            w, h = h, w
         return h > w
</file context>

Suggested change

	if rotation % 180 != 0:
	if rotation % 180 == 90: