Research Digest: 2160p at 1.5H CSF support (upstream c2155d6cd)¶

Port date: 2026-06-01 Upstream author: Christos Bampis, Netflix Upstream SHA: c2155d6cdc1796329783dcb9ce8ce5cf3d7e1dc5

Summary¶

The 2160p display at 1.5x picture height viewing distance has the same angular resolution as 1080p at 3H: 1.5 * 2160 = 3.0 * 1080 = 56.55 ppd. barten_watson_blend_csf{,_mae} previously fell through to the else-branch (assertion or undefined behaviour) for this combination. The fix adds the equivalence branch before the existing 2160@3H branch.

Validation¶

Upstream adds 16 pinning assertions in test_barten_csf.c verifying byte-for-byte equality between csf(scale, theta, 1.5, 2160) and csf(scale, theta, 3.0, 1080) for all 8 (scale, theta) combinations. These tests are ported verbatim.