948697ef0d9f3d8ff7dcfc4f488651c40016e719
2 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 claude-noether
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948697ef0d |
phase1/stage1: bit-exact gate for the frame-scaled luma IDCT 4x4
Adds test_idct_bitexact that exercises daedalus_decoder_flush_frame
end-to-end with random coefficients and compares every output byte
against an inline C reference of the H.264 §8.5.12.1 1D butterfly.
Closes the validation gap from the previous PR ("dispatch succeeds"
becomes "dispatch is bit-exact").
What's tested:
- 320×240 coded frame (300 MBs), enough to cover multiple workgroups
of the V3D shader (16 blocks/WG → ≥30 WGs)
- Per-MB → flat-raster block layout consistent with flush_frame
- Random coeffs in [-512, 511] (same range as daedalus-fourier
cycle-6 M1 gate)
- Inline C reference: H.264 §8.5.12.1 butterfly with column-major
block layout, +32 rounding, >>6, add-to-predicted (=0), clip255 —
mirrors daedalus-fourier tests/h264_idct4_ref.c
Verified on hertz (Pi 5 / V3D 7.1 / daedalus-fourier 0.1.0):
$ ctest --test-dir build --output-on-failure
Start 1: smoke
1/2 Test #1: smoke ............................ Passed 0.16 sec
Start 2: idct_bitexact
2/2 Test #2: idct_bitexact .................... Passed 0.03 sec
100% tests passed, 0 tests failed out of 2
Bit-exact PASS first try — daedalus-fourier's V3D IDCT 4x4 shader
produces identical pixels to the C reference for all 4800 blocks in
the test frame. Validates BOTH the shader correctness AND the
frame-batched-dispatch correctness (this is the first time
n_blocks > ~30 has been exercised at the recipe-dispatch layer; the
substitution arc only ever called with n_blocks=1).
What is NOT tested by this PR (deferred to follow-ons):
- Non-zero predicted pixels — flush_frame zero-initialises scratch_y,
so the IDCT-ADD reduces to clip255(IDCT). Real predicted comes
from Stage 2a intra prediction.
- Z-scan permutation between FFmpeg's per-MB coeffs layout and our
per-MB → flat raster — the test uses its own coefficient generator
that already matches our layout, so it doesn't exercise the
permutation. The libavcodec-intercept patch is where the
permutation lands and gets validated against real H.264 streams.
- Chroma 4×4 IDCT.
- IDCT 8×8 (High profile).
Stacked on noether/phase1-stage1-idct (PR #3, the frame-scaled
dispatch). Rebase on main after #3 lands; the diff is purely additive
(one new test file + 5 lines of CMake).
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claude-noether
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08080f062c |
scaffold: CMake + API skeleton + smoke test
First code on daedalus-decoder per the Phase 1 decisions merged 2026-05-24.
Repo skeleton only — no Vulkan pipeline yet, no shaders, no libavcodec
intercept. Establishes the build shape so subsequent work has a place
to land.
Layout:
LICENSE BSD-2-Clause (matches daedalus-fourier)
.gitignore build/, CMake artefacts, *.spv
CMakeLists.txt top-level — finds daedalus-fourier
≥0.1.0 via pkg-config (per §9.6
decision: find_package, pinned to
tagged release; .pc consumed via
pkg_check_modules until we ship a
CMake config), Vulkan via
find_package, builds static lib
+ smoke test, GNUInstallDirs install
include/daedalus_decoder.h public API surface:
- daedalus_decoder_{create,destroy,
version,has_qpu}
- daedalus_decoder_set_output_format
(NV12 default, RGBA opt-in per §5)
- daedalus_decoder_append_mb +
struct daedalus_decoder_mb_input
(matches §3 per-MB descriptor)
- daedalus_decoder_flush_frame
(per-frame submit + wait)
- daedalus_decoder_export_dmabuf
(Vulkan-native VkImage export per
§9.4 decision)
Dimensions are CODED frame size
(mod-16), not displayed — caller
translates from SPS + crop offsets.
src/internal.h internal mb_desc struct (matches
shader std430 layout, to be nailed
down once shaders exist) + per-ctx
state
src/daedalus_decoder.c stub bodies:
- create/destroy with proper resource
lifecycle
- append_mb validates + writes CPU
staging buffers (no GPU yet)
- flush_frame returns -2 (not
implemented) — Phase 1 work
- export_dmabuf returns -1
- has_qpu / version diagnostics
tests/test_smoke.c link + lifecycle test: bad dims
reject, OOB MB reject, null inputs
reject, raster-order enforcement,
mid-frame format-change reject,
incomplete-frame flush reject.
On hosts without V3D7 Vulkan,
SKIPs gracefully (returns 0).
Verified on hertz (Pi 5 / V3D 7.1 / Mesa V3DV via daedalus-fourier
0.1.0):
$ cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
$ cmake --build build
$ ctest --test-dir build --output-on-failure
Test #1: smoke ... Passed
$ ./build/test_smoke
daedalus-decoder version: 0.0.1
ctx created: 1920x1088, has_qpu=1
smoke OK
Note the coded-vs-displayed dims trap: 1080p H.264 has coded height
1088 with 8 rows cropped via SPS frame_cropping_*. Header docstring
on daedalus_decoder_create() spells this out so future callers don't
hit the multiple-of-16 reject (smoke test caught it during scaffold
write).
Next: Phase 1 implementation begins — IDCT 4×4 / 8×8 frame-scaled
dispatch (reusing daedalus-fourier shaders per Appendix A), intra
prediction wavefront, reconstruct stage, NV12 output via dmabuf
export. Smoke test grows from "ctx lifecycle works" to
"I-frame-only Baseline decode bit-exact vs FFmpeg reference".
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