@ -47,12 +47,15 @@ Checkboxes may be marked complete only when the implementation and the verificat
- [x] Implement allocation-free SIMD-first HEVC inverse quantization for flat and custom scaling lists, 4/8/16/32 transforms, transform-skip scaling rules, extended precision, signed normalization shifts, and transform-range clipping. Store compact and transform-sized scaling matrices in one contiguous parameter-set allocation so the hot path can widen consecutive weights without coordinate division.
- [x] Derive each reference-unit availability flag from coding-tree, slice, tile, constrained-intra, and picture-boundary state, then connect prediction to transform-unit traversal and the bounded item decoder lifecycle.
- [x] Register the bounded `hvc1` still-image decoder, reconstruct the selected PPS/SPS picture, crop the conformance window directly in the pooled row converter, and pass the native planes through the shared SIMD-first H.273 pipeline.
- [x] Compare native HEVC planes byte-for-byte with HM 18 output for four item payloads extracted from independently produced HEIC files: two 8-bit 4:2:0 grid tiles, a cropped 8-bit 4:2:0 grid tile, and an 8-bit 4:4:4 wavefront tile.
- [x] Compare complete HEIC presentation output with libheif 1.23.1 and libde265 1.1.1 for single images, multi-tile grids, an auxiliary alpha image, an ICC-bearing image, and a 4:4:4 wavefront image. Exact native-plane tests remain the codec oracle because libheif's selected fused 4:2:0 RGB path uses nearest-neighbor chroma while ImageSharp uses its higher-quality signaled-position interpolation.
- [ ] Add permanent HEVC 8/10/12-bit monochrome, 4:2:0, 4:2:2, and 4:4:4 fixtures covering every exposed profile and Range Extensions tool, with exact native-plane references from HM or another independent decoder.
- [x] Implement the shared SIMD-first YUV/CICP paths in both directions for AV1 and HEVC bit depths, chroma formats, ranges, matrix coefficients, transfer functions, color primaries, and chroma positions, with scalar fallback only after the available vector widths are exhausted.
- [ ] Complete the independently generated AV1 and HEVC conformance matrix for every supported color-signaling combination before closing the Phase 5 color exit gate.
- [x] Apply ICC conversion only after the SIMD YUV/CICP stage, alpha composition, grid assembly, and presentation transforms have produced the presented RGB image; retain ImageSharp's shared ICC converter and optimize reusable bulk kernels rather than creating a HEIF-specific color-management implementation.
- [ ] Verify ICC preservation, conversion, compaction, and metadata skipping for grids, alpha-composited images, every presented sequence frame, and the completed HEVC path.
- [x] Independently encode AVIF primary, grid, alpha-auxiliary, and two-frame sequence vectors with libavif 1.4.2/libaom 3.14.1; verify exact profile preservation, non-sRGB conversion, canonical-sRGB compaction, non-sRGB compact preservation, metadata skipping, every presented frame, and unchanged composed alpha.
- [ ] Repeat the same matrix for HEVC primary, grid, alpha-auxiliary, and sequence paths after HEVC reconstruction is complete.
- [ ] Repeat the complete ICC preservation, conversion, compaction, and skipping matrix for HEVC primary, grid, alpha-auxiliary, and sequence paths. The current libheif comparison establishes presentation interoperability for one ICC-bearing still image but does not close these separate color-management contracts.
- [ ] Benchmark representative 8/10/12-bit end-to-end AVIF and HEIC color pipelines with and without ICC conversion, recording absolute timings and allocations before marking Phase 5 complete.
- [x] Add permanent frame-wide `Av1ColorConversionBenchmarks` coverage for sequential 1920x1080 YUV 4:2:0 conversion in both directions at 8, 10, and 12 bits, including managed-allocation reporting.
- [x] Record the .NET 10 short-run AV1 baseline on 2026-08-25. SIMD decode measured 4.025/2.803/2.742 ms and encode measured 3.750/2.555/2.450 ms at 8/10/12 bits with 488-744 B allocated per frame. Forced-scalar decode measured 31.15/29.47/28.40 ms and encode measured 19.19/15.77/15.14 ms, making the normal SIMD pipeline 7.7-10.5 times faster for decode and 5.1-6.2 times faster for encode on this machine.
@ -279,22 +282,22 @@ This assessment is based on the current source after the upstream ImageSharp mer
- Item IDs are resolved as keys rather than list indices; metadata children are indexed and parsed in dependency order rather than physical order.
- Item property associations now preserve physical `ipco` indices, apply one-based 7-bit or 15-bit indices and essential flags, associate by item ID, and reject arbitrary unknown essential properties.
- Item locations now support bounded file-relative and `idat`-relative storage, multiple ordered extents, versioned item IDs, 0/4/8-byte registered field sizes, and 64-bit offsets. Referenced-item construction method two and external data references remain explicitly unsupported.
- Grid derived-image decoding now parses both registered descriptor widths, resolves the ordered `dimg` cells, validates tile count, coding format, dimensions, canvas coverage, and edge overlap, then composes the output through ImageSharp row buffers. Unsupported grid tile codecs can select only a decodable thumbnail of the same primary grid. Independent AV1 and JPEG grid fixtures are still required, and HEVC grids remain blocked on the HEVC decoder.
- Alpha auxiliary decoding now recognizes `auxC`, `auxl`, and `prem`, supports a direct auxiliary image/grid and the per-color-grid-tile form, preserves normalized alpha through `L16`/`Rgba64`, box-resamples differing plane sizes, and reports alpha presence. HEVC alpha remains blocked on the HEVC image-item decoder, while independent AVIF alpha fixtures are still required against the incomplete AV1 reconstruction pipeline.
- Grid derived-image decoding now parses both registered descriptor widths, resolves the ordered `dimg` cells, validates tile count, coding format, dimensions, canvas coverage, and edge overlap, then composes the output through ImageSharp row buffers. Unsupported grid tile codecs can select only a decodable thumbnail of the same primary grid. HEVC grids are exercised by independent libheif output and exact HM tile-plane references; independent AV1 and JPEG grid fixtures are still required.
- Alpha auxiliary decoding now recognizes `auxC`, `auxl`, and `prem`, supports a direct auxiliary image/grid and the per-color-grid-tile form, preserves normalized alpha through `L16`/`Rgba64`, box-resamples differing plane sizes, and reports alpha presence. HEVC auxiliary-alpha presentation is exercised against independent libheif output, while independent AVIF alpha fixtures are still required against the incomplete AV1 reconstruction pipeline.
- Clean aperture, image rotation, and image mirror properties now validate their registered payloads, exact integer crop geometry, and essential associations; affect Identify dimensions; and reuse ImageSharp's optimized crop/rotate/flip processors after auxiliary alpha composition in the MIAF-defined order. Independent transform vectors must still verify every crop/rotation/mirror/alpha combination.
- Decode now resolves `cdsc`-associated Exif and `application/rdf+xml` XMP items for the primary still image, validates the declared Exif TIFF-header offset, and attaches the payloads through ImageSharp's existing profile types before presentation transforms. Independent AVIF, HEIC, and HIF metadata fixtures and Identify-time profile reporting remain required.
- ICC and `nclx` CICP color properties are now associated with the presented color item instead of global parser state, validated, and exposed on Decode and Identify through the existing ImageSharp profiles. AV1 decode requires specified sequence-header fields and the range flag to match `nclx`, uses the property only for fields the bitstream leaves unspecified, and exposes the effective sequence-header CICP description when no property is present. Independent libavif fixtures verify exact ICC byte preservation, observable non-sRGB conversion, canonical-sRGB compaction, non-sRGB compact preservation, and metadata skipping for primary, grid, alpha-composited, and every presented sequence frame; the alpha vector also verifies that ICC conversion does not alter composed alpha. Identify-time bitstream fallback, independent CICP vectors, and HEVC integration remain required.
- Pixel aspect ratio now preserves the complete unsigned spacing pair, affects Decode and Identify through ImageSharp's existing unitless resolution metadata, and follows quarter-turn presentation rotation. Independent grid, rotation, and maximum-spacing fixtures remain required.
- AV1 codec configuration is now retained per `av01` image item rather than in decoder-global state. Decode requires the property, validates its fixed record against the item's sequence header and any associated `pixi` channel depths, and requires matching configurations across grid tiles. Identify now reports the configuration's 8/10/12-bit precision and monochrome shape. The optional `configOBUs` sequence is bounded and validated, including its mandatory size fields, first-position/at-most-one sequence-header rule, the image item's exactly-one sequence-header rule, and exact comparison of a repeated configuration header with the item header. Content light-level and mastering-display color-volume information are decoded from the bounded `clli` and `mdcv` image properties and matching AV1 HDR metadata OBUs, with the representations' distinct fixed-point precision, grid/property precedence, and `SkipMetadata` behavior preserved. The still-image `cclv`, `amve`, `reve`, and `ndwt` properties preserve content-volume, ambient-viewing, mastering-environment, and diffuse-white descriptions without importing their video-SEI or sample-entry state models. Independent fixtures and encoder preservation remain required. HEVC `hvcC` is now associated with each `hvc1` image item, structurally validated through its VPS/SPS/PPS arrays, and used to report encoded precision and monochrome shape; item-payload validation is implemented for the bounded decoder path, while pixel reconstruction remains incomplete.
- AV1 codec configuration is now retained per `av01` image item rather than in decoder-global state. Decode requires the property, validates its fixed record against the item's sequence header and any associated `pixi` channel depths, and requires matching configurations across grid tiles. Identify now reports the configuration's 8/10/12-bit precision and monochrome shape. The optional `configOBUs` sequence is bounded and validated, including its mandatory size fields, first-position/at-most-one sequence-header rule, the image item's exactly-one sequence-header rule, and exact comparison of a repeated configuration header with the item header. Content light-level and mastering-display color-volume information are decoded from the bounded `clli` and `mdcv` image properties and matching AV1 HDR metadata OBUs, with the representations' distinct fixed-point precision, grid/property precedence, and `SkipMetadata` behavior preserved. The still-image `cclv`, `amve`, `reve`, and `ndwt` properties preserve content-volume, ambient-viewing, mastering-environment, and diffuse-white descriptions without importing their video-SEI or sample-entry state models. Independent fixtures and encoder preservation remain required. HEVC `hvcC` is associated with each `hvc1` image item, structurally validated through its VPS/SPS/PPS arrays, and used to report encoded precision and monochrome shape. The bounded decoder reconstructs exact native planes for the verified 8-bit 4:2:0 and 4:4:4 item payloads; the remaining profile, bit-depth, chroma-layout, and Range Extensions matrix is not yet established.
- Several image-item properties and relationships remain missing or parsed without fully affecting output.
- Identify and decode now use the same bounded metadata parser and both validate the complete leading file type box. The parsed state is still mutable and Identify does not yet report the complete bit depth, color, profile, or transform model.
### HEVC decoder and encoder
- `Heif4CharCode` recognizes `hvc1` image items, `HevcCodecConfiguration` validates and associates the bounded `hvcC` property, Identify reports its HEVC precision and monochrome shape, and `HeifCompressionFactory` registers the bounded HEVC still-image decoder.
- The HEVC path validates NAL headers and RBSP escaping, links `hvcC` VPS/SPS/PPS structures through Range Extensions, parses one length-delimited base-layer IDR picture, and reconstructs its complete intra-coded coding tree. It includes CABAC, transform traversal, coefficient decoding, intra prediction, inverse quantization and transform, PCM, deblocking, sample-adaptive offset, and allocator-owned native `ushort` planes for monochrome, 4:2:0, 4:2:2, 4:4:4, separate-color-plane, and 8-through-16-bit samples. The item adapter converts the SPS conformance window directly through the shared pooled SIMD-first H.273 pipeline and preserves the effective container-or-VUI CICP description. The internal HEVC suite passes, but independent pixel comparisons for the repository's HEIC fixtures and the complete color/precision/layout matrix remain open, so conformance is not yet established.
- The HEVC path validates NAL headers and RBSP escaping, links `hvcC` VPS/SPS/PPS structures through Range Extensions, parses one length-delimited base-layer IDR picture, and reconstructs its complete intra-coded coding tree. It includes CABAC, transform traversal, coefficient decoding, intra prediction, inverse quantization and transform, PCM, deblocking, sample-adaptive offset, and allocator-owned native `ushort` planes for monochrome, 4:2:0, 4:2:2, 4:4:4, separate-color-plane, and 8-through-16-bit samples. The item adapter converts the SPS conformance window directly through the shared pooled SIMD-first H.273 pipeline and preserves the effective container-or-VUI CICP description. Four real item payloads now match HM 18 native planes exactly, covering 8-bit 4:2:0 grids, cropping, 8-bit 4:4:4, and wavefront entry points. Complete images covering grids, auxiliary alpha, ICC, and 4:4:4 presentation also match independent libheif output within the documented chroma-reconstruction tolerance. High bit depths, monochrome, 4:2:2, remaining Range Extensions tools, and the complete color matrix still require independent fixtures before HEVC conformance is established.
- There is no HEVC encoder. The current HEIC-branded encoder writes a legacy JPEG payload and therefore cannot provide HEIC output.
- Existing HEVC tests prove container identification only; they do not decode or compare HEIC pixels.
- Permanent HEVC conformance tests compare extracted item planes exactly with HM output and complete presented images with pinned libheif/libde265 reference PNGs. The fixtures do not yet cover the complete exposed profile matrix.
### AV1 decoder
@ -469,7 +472,7 @@ Implement and verify in dependency order:
- [ ] Intra prediction for every luma and chroma mode, including strong intra smoothing and constrained prediction rules.
- [x] Implement and verify the allocation-free SIMD-first predictor primitive for all 35 modes, 4/8/16/32 blocks, and 8/10/12-bit samples.
- [x] Implement reconstructed-plane reference collection, substitution, asymmetric chroma-unit handling, and reference-filter selection from caller-owned availability and scratch spans.
- [] Build each availability flag from reconstructed-plane and coding state, and connect the predictor to transform-unit traversal.
- [x] Build each availability flag from reconstructed-plane and coding state, and connect the predictor to transform-unit traversal for the independently verified 8-bit 4:2:0 and 4:4:4 item paths.
- [ ] Scaling lists, inverse quantization, transform skip, every required inverse transform, range-extension precision, and lossless reconstruction.
- [x] Implement allocation-free SIMD-first inverse DCT for every 4/8/16/32 width and height combination, the four-by-four intra-luma inverse DST, normative intermediate and residual clipping, and saturated prediction addition for 8/10/12-bit samples. Verify normal and forced-scalar execution against fixed results and a dense scalar oracle.
- [x] Implement the SIMD-first inverse-quantization primitive for flat and scaling-list paths across every transform size, component matrix, prediction mode, transform-skip scaling rule, signed normalization direction, and range-extension precision path.
@ -485,6 +488,9 @@ Implement and verify in dependency order:
- [ ] Deblocking and sample-adaptive offset for every signaled luma/chroma and bit-depth path.
- [ ] Tiles, wavefront entry points, dependent slices, and all other parallelization syntax permitted by the exposed still-image profiles.
- [ ] Supplemental enhancement information that changes image presentation or metadata exposed by ImageSharp.
- [x] Establish exact HM 18 native-plane conformance for four real 8-bit item payloads covering 4:2:0, 4:4:4, cropping, multiple grid positions, and wavefront entry points.
- [x] Establish independent libheif/libde265 presentation comparisons for single images, grids, auxiliary alpha, ICC, and 4:4:4 output without weakening the exact native-plane codec oracle.
- [ ] Establish exact native-plane conformance for 8/10/12-bit monochrome, 4:2:0, 4:2:2, and 4:4:4 across every exposed HEVC profile and required Range Extensions tool.
Each subsystem keeps a specification-shaped scalar oracle derived from the HEVC specification and the pinned implementation reference, while production hot paths are designed SIMD-first with scalar fallback. No valid syntax in the exposed HEIC profiles may terminate in an unsupported branch or silently omit a normative reconstruction stage.
James Jackson-South
2 months ago
