Hyperframes Render Stretch Repro

Minimal reproduction for a suspected Hyperframes render bug where the video after an image transition overlay is rendered anisotropically stretched even though the source MP4 has correct 16:9 geometry.

This repository starts from:

npx hyperframes init repro --non-interactive --example blank

The only meaningful changes are in repro/index.html plus the added test media in repro/videos/ and repro/assets/.

What To Render

The composition uses three synthetic 1920x1080 MP4s and one PNG transition overlay:

• repro/videos/clip_01_reference_grid.mp4
• repro/videos/clip_02_after_transition_grid.mp4
• repro/videos/clip_03_after_second_transition_grid.mp4
• repro/assets/transition_overlay.png

Each MP4 contains a grid, a center 400x400 square, rulers, and burned-in local time/frame labels. If the render stretches the next video taller, the square becomes a rectangle and the vertical/horizontal rulers no longer match.

All source clips are verified as:

• 1920x1080
• SAR 1:1
• DAR 16:9
• 25 fps
• CFR
• H.264 High Profile, yuv420p

See repro/source_specs.txt for the exact ffprobe output.

Clean Reproduction Steps

From a fresh clone:

git clone https://github.com/brian-t-allen/hyperframes-render-bug.git
cd hyperframes-render-bug/repro
npm run check
npm run render -- -o /tmp/hyperframes-stretch-repro.mp4 --fps 25 --quality draft --workers 2 --no-browser-gpu

Open /tmp/hyperframes-stretch-repro.mp4 and inspect the transition boundaries.

Timeline

• 0.000s - 32.600s: clip 01
• 31.600s - 33.600s: first transition overlay
• 32.600s - 64.360s: clip 02
• 63.360s - 65.360s: second transition overlay
• 64.360s - 124.360s: clip 03

The expected result is that the center square remains square for all three clips. The source clips themselves do not contain a stretch; any stretch in the rendered output is introduced during Hyperframes rendering.

When reporting the bug, include both the composition timestamp and the burned-in clip timestamp/frame visible in the frame.