Research-2091: restoring silent-reverted test seams¶

Finding¶

The BUG-048 silent-revert ledger identified three historical test slices:

ba5cdec32 added a direct VMAF_PIX_FMT_YUV400P allocation test;
1bdbd29f2 added explicit --precision and --sycl_device parser cases;
8f884b1f6 added Metal registration smoke cases and Metal/HIP registration invariant notes.

At exact origin/master 4e6916d16ac57647105d14a47a6680117d6b5738, the YUV400P and explicit CLI cases were genuinely absent. The implementation contracts still worked, but no focused test would fail if a later change reintroduced chroma allocation for monochrome pictures, ignored an explicit SYCL device, or drifted one of the three accepted precision modes.

The Metal part had a different current-tree answer. The historical commit added six lookups, but float_ansnr_metal was later removed with the ANSNR backend. All five surviving names are already covered by core/test/test_metal_kernel_registration.c, and the newer core/test/test_metal_kernel_coverage_audit.c checks the complete 17-extractor inventory against the feature registry. Its temporal table also pins the two motion descriptors from the historical slice. Duplicating those five lookups in test_metal_smoke.c would add no observable contract and would split the registration authority again. The invariant prose itself was still missing, so it is restored against the current canonical tests; the matching HIP note points at the existing comprehensive test_hip_smoke.c registration table.

Coverage audit¶

Contract	Current result	Action
YUV400P public allocation geometry	Consumer tests allocate YUV400P, but none pins both zero chroma geometries and pointers on standard and odd dimensions through `vmaf_picture_alloc()`	Restore a focused public-seam test in `test_picture.c`
`--precision=max`, `legacy`, and numeric `6`	Default/compatibility tests cover indirect overrides, not the three explicit parser forms	Restore exact parser cases and resolved formats
`--sycl_device 3`	Backend selection covers default device 0 only	Restore explicit-device parsing and ensure SYCL remains enabled
Five live Metal registrations	Present in the dedicated eight-extractor registration test and the 17-kernel audit	Superseded; do not duplicate in runtime smoke
Registration invariant prose	Missing from Metal and HIP backend notes	Restore with current paths and authoritative test roles

The YUV400P check records its geometry before unref and releases the picture before asserting it, so a failed geometry assertion does not leak test-owned memory. The standard and odd-size cases share one public-seam helper without changing production code.

Alternatives considered¶

Alternative	Result
Cherry-pick the three historical commits	Rejected. Paths moved from `libvmaf/` to `core/`, Vulkan and Metal ANSNR were removed, and later test-structure rules changed.
Re-add all five Metal lookup functions to `test_metal_smoke.c`	Rejected. Current dedicated registration and full-kernel audit tests already assert the same names and temporal flags.
Restore only the two genuinely missing executable seams and update invariant authority	Chosen. It closes the live gaps while preserving one canonical registration inventory.

No ADR is needed: the change restores tests and documentation for existing behavior and makes no architectural, policy, public-surface, or runtime decision. No Netflix golden assertion is touched.

Red-cap and verification¶

Before the restoration, an exact-source sentinel failed with the missing YUV400P function, four CLI functions, five historical Metal smoke functions, and both backend invariant headings. That sentinel intentionally modeled the historical file shape; the source audit above then established that the five Metal functions were already semantically superseded elsewhere.

After restoring the live gaps, a clean CPU Meson build passed test_picture and test_cli_parse (2/2). A repository-aware static audit checks the five live historical Metal names in both the feature registry and the current registration/audit sources, including temporal membership for float_motion_metal and integer_motion_metal.

Reproducer¶

Configure a clean CPU-only build and run the restored executable contracts:

meson setup /tmp/vmafx-bug048-tests core \
  -Denable_cuda=false -Denable_sycl=false -Denable_hip=false \
  -Denable_metal=disabled -Denable_dnn=disabled -Denable_mcp=false
meson compile -C /tmp/vmafx-bug048-tests
meson test -C /tmp/vmafx-bug048-tests test_picture test_cli_parse \
  --print-errorlogs

The full CPU fast-suite regression gate is:

meson test -C /tmp/vmafx-bug048-tests --suite fast --print-errorlogs