open-standards/wai/platform-decode-conformance/grain-free-av1

grain-free-av1 — a refinement over the platform-decoded floor

The corpus of extensions/platform-decode.md §6: a grain-free wai.video.av1 stream, which every conforming AV1 decoder decodes to the same frames, as the base of wai.video.int_refine layers written against its reference decode.

Equivalence. A conforming sink makes the base from the frames its decoder gives (I420, in output order) and the probe's outcome for that decoder, converts them to RGB8 units (§6.3), and, replaying each case of cases.json, reports what the case states at every step and ends with every unit at the stated stage, producer, tier and stage hash, and the stated clip hash. It refuses base-grain.wai as a base (av1_film_grain).

Files

• base.wai — WAI1, wai.video.av1: eight frames of 160×96, 8-bit 4:2:0, codec string av01.0.31M.08, every sequence header with film_grain_params_present 0. Encoded with rav1e from a source clip that wai_av1_refine_vectors computes (integer ramps, a moving checkerboard and a band of stripes), at quantizer 140, one thread, low latency.
• base-grain.wai — the same source, encoded with photon-noise film grain: refused as a base.
• base.i420 — the reference decode of base.wai (libdav1d): each frame's luma plane, then Cb, then Cr, rows tightly packed, frames in output order.
• probe.json — §6.2's probe of base.wai: the codec string and coded size a page configures, each frame's SHA-256 over its I420 samples (frame_sha256) and the clip digest.
• layer1.wai, layer2.wai — WAI1, wai.video.int_refine, WIR1 with the identity predictor: layer 1 (step 6) over the base's RGB8 units toward the source clip, layer 2 (step 1) over layer 1's output, which reaches the source exactly.
• layer1-over-grain.wai — layer 1's payload with refines naming base-grain.wai.
• cases.json — stage0_sha256 (each unit's stage-0 hash) and the cases: stage0, one-layer, two-layers, two-layers-reference, two-layers-out-of-order, unprobed and film-grain. Each states its base, the decoder whose frames make it (reference and probe-matched at decode-equivalence, unprobed at none), its steps (an offer at step index + 1 ms, or expire@t), and what a sink reports and holds.

Verifiers

• wai_av1_refine_vectors verify . (from ../../wai-rs, feature av1_refine_vectors, libdav1d): decodes base.wai and requires base.i420; refuses base-grain.wai before decoding it; regenerates every other file but the two streams byte for byte. gen writes them from the committed streams; gen --encode encodes the streams again.
• cargo test --no-default-features --features staged --test av1_refine (add av1_base for the libdav1d decode): every case through staged::StageSink, the probe and stage-0 hashes, the grain flag set alone, and one changed sample.
• python3 -I verify.py [--dav1d PATH]: the second implementation, standard library only, with the sink of ../../staged-conformance/staged_verify.py; --dav1d decodes the stream with the dav1d tool (section 5 input) and requires base.i420.
• node ../../wai-web/demo/verify_av1_refine_wasm.mjs <pkg-node/wai_web.js>: every case through wai-web's wasm32 StageSink from base.i420.
• node ../../wai-web/demo/verify_av1_refine.mjs (Playwright): the page decodes base.wai through the browser's WebCodecs, puts each decode to the probe, and replays every case from the no-preference decode's frames, in each browser WAI_AV1_BROWSERS names (Chromium and WebKit by default). What it measured is in platform-decode §6.4.