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ImageSharp/tests/Images/Input/Heif/Av1/Conformance/README.md

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AV1 reconstruction conformance fixtures

These fixtures provide independent reference output for AV1 reconstruction and AVIF presentation tests. ImageSharp output is compared exactly with the retained native YUV planes and presented PNG files; the tests do not use a tolerance.

Provenance

The source images and original AVIF files come from libavif/tests/data at commit 062e582e8afda88e6baf988fdcf046a801efa0f5. Their licenses are recorded in libavif's tests/data/README.md and continue to apply to the derived fixtures. This includes the unrestricted Kodak image, the CC BY 3.0 Cosmos Laundromat frame, and files distributed under libavif's BSD-2-Clause license.

Reference files were generated with scalar builds of:

  • libaom commit 03087864cf4bea6abb0d28f95cf7843511413d8f;
  • libavif 1.4.2 from commit 062e582e8afda88e6baf988fdcf046a801efa0f5, linked to that libaom build.

The reference builds use AOM_TARGET_CPU=generic and disable libyuv. Native reconstruction therefore comes from libaom, and AVIF presentation comes from libavif's own conversion path, without architecture-specific SIMD or ImageSharp code.

File conventions

  • .avif files exercise the complete container and presentation path.
  • .bit files contain the exact AV1 elementary-stream payload used by reconstruction tests.
  • -libaom.yuv files contain headerless planar Y, U, and V reference samples. Samples above eight bits are stored as little-endian 16-bit values.
  • -libaom-y4m.yuv files retain the Y4M header together with the native planar frame.
  • -libaom.y4m files retain the Y4M header together with the native sequence frames selected for comparison.
  • .png files contain the eight-bit RGBA presentation reference produced by the pinned scalar libavif build.

Coverage

Fixture family Coverage
libavif-kodim23, libavif-cosmos1650, libaom-cosmos1650 Baseline 8-, 10-, and 12-bit reconstruction, chroma subsampling, and active deblocking
*-cdef-* Active CDEF with loop restoration disabled
*-superres-* Active horizontal super-resolution with CDEF and restoration disabled
*-restoration-* Wiener and self-guided loop restoration
*-restoration-superres-* Restoration after super-resolution, including 10-bit 4:2:2 clipped-edge transform coverage
libavif-profile-* The 8-, 10-, and 12-bit matrix across monochrome, 4:2:0, 4:2:2, and 4:4:4
*-palette-* Luma and chroma palette prediction
*-intrabc-* Intra-block copy at every supported bit depth
*-lossless-* Lossless quantization, reversible transforms, and exact presentation
*-film-grain-* Full and restricted range, monochrome, identity matrix, 8/10/12-bit synthesis, overlap, and odd frame dimensions
libaom-av1-1-b10-23, libaom-av1-1-b10-24 Official ten-bit dependent-frame film grain and monochrome sequence reconstruction
libavif-progressive-draw-points-8b A real two-layer color item whose final frame uses single-reference inter reconstruction, plus its progressive auxiliary alpha item
libavif-webp-logo-average-compound A 19-frame YUV444 image sequence whose retained references reach equal-weight compound inter reconstruction
libavif-webp-logo-distance-weighted-compound Selectable distance-weighted compound prediction
libavif-webp-logo-wedge-compound Wedge compound prediction with both signaled mask orientations
libavif-webp-logo-difference-weighted-compound Difference-weighted compound prediction with both mask orientations
libavif-webp-logo-inter-intra Smooth and wedge inter-intra prediction
libavif-webp-logo-obmc Above and left overlapping motion compensation through a 19-frame dependent sequence
libavif-rotating-grid-local-warp Multi-sample local affine projection and warped prediction through a two-frame dependent sequence
libavif-rotating-grid-global-warp Non-translational rotation/zoom GLOBALMV prediction through a two-frame dependent sequence

The corresponding tests also assert the syntax required by each family before comparing output. This prevents an inactive tool or an incorrectly substituted stream from passing solely because its final pixels happen to match.

Official ten-bit sequence fixtures

The libaom-av1-1-b10-23-film-grain-50.ivf and libaom-av1-1-b10-24-monochrome.ivf streams are the official files from libaom's test-data bucket. Their SHA-1 values are 2F883C7E11C21A31F79BD9C809541BE90B0C7C4A and 03A8D002594CCC51932332002BB6F9837EF46D0F, exactly matching test/test-data.sha1 at pinned libaom commit 03087864cf4bea6abb0d28f95cf7843511413d8f. Their SHA-256 values are C36CF5AB6A2E9E27C212C06863759B60791E3FA681A0800B5D57FD4192EF29CB and 6A1B0729305A167F10737A5375F0570139F055BCD7916DF260B653AB2210ADC1.

The retained native references were generated from the pinned generic libaom build with:

aomdec --threads=1 --output=libaom-av1-1-b10-23-film-grain-50-libaom.y4m libaom-av1-1-b10-23-film-grain-50.ivf
aomdec --threads=1 --output=libaom-av1-1-b10-24-monochrome-libaom.y4m libaom-av1-1-b10-24-monochrome.ivf

The film-grain Y4M SHA-256 is A1B553BE140F48ABDDB2A6D39917AB714BA03AC7FFD6359EAA1CB0D89C985A3B, and the monochrome Y4M SHA-256 is 7394BC8146485D200BFDEC62E170482F8B1A85A64D21FAC62D10116FB1BB140D. The tests decode and compare all ten frames from each sequence exactly under normal and scalar dispatch. The film-grain stream retains dependent ungrained references while applying ten-bit grain to each displayed 352x288 YUV420 frame; the monochrome stream verifies every 320x180 ten-bit luma sample without manufacturing chroma in ImageSharp. Both sequences also run through a constrained tracked allocator.

Progressive dependent-frame fixture

The libavif-progressive-draw-points-8b.avif fixture is the unmodified tests/data/draw_points_idat_progressive.avif file from the pinned libavif tree. Its SHA-256 is 077AB2AD1E46DD912A973E4F024CB1EB242A08298BE2DBF1A52A058E88C48A4A. It was generated with:

./avifenc -q 100 --progressive ../tests/data/draw_points.png ../tests/data/draw_points_idat_progressive.avif

The primary color item's a1lx property divides its logical 72-byte AV1 payload into a 55-byte base layer and a 17-byte dependent layer. The container stores those layers in separate iloc extents at AVIF offsets 511 and 583. The .bit fixture concatenates those two logical color extents; it does not copy the physically adjacent auxiliary-alpha extent between them.

Exact pinned libaom decodes the corrected logical payload into two 33x11 YUV444 frames. Both frames' 1,089 color samples match the corresponding first three planes of the pinned libavif YUV444-alpha outputs exactly. The retained Y4M contains both progressive YUV444-alpha frames, and the PNG contains pinned libavif's final RGBA presentation. The production-path test selects the second native frame, requires inter-coded blocks in the final ImageSharp frame, and compares both native color and final presentation without a tolerance.

Equal-average compound fixture

The libavif-webp-logo-average-compound.avif fixture was encoded from the pinned libavif tree's tests/data/webp_logo_animated.y4m source. The source SHA-256 is 0872208D9C19B68B10A1647FA6849CFC4E2B21A19561ACD672E0629C70EFACA2. It was generated with:

./avifenc -j 1 -c aom -s 4 -q 80 -a enable-dist-wtd-comp=0 -a enable-masked-comp=0 -a enable-interintra-comp=0 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-average-compound.avif

Pinned scalar libavif generated the retained references with:

./avifdec -j 1 -c aom --index 18 libavif-webp-logo-average-compound.avif libavif-webp-logo-average-compound-libaom.y4m
./avifdec -j 1 -c aom --index 18 libavif-webp-logo-average-compound.avif libavif-webp-logo-average-compound-libavif.png

The AVIF SHA-256 is 7919049D367EEDB7C965E170309D6759660DDBFD4BB1AEF9496F9D66E314846A. The retained frame-18 Y4M SHA-256 is 41FF2408DEB473D5483F3398882DF7F7AB6C7D376561C19798881595EB0C5C0C, and the frame-18 PNG SHA-256 is BCFABC1E1C7E17D8ECB40569849A04FFAC6CA1FCDF613F217B33816CA47337AC. The test decodes every preceding hidden and shown sample to establish the same retained-reference state before comparing all native Y, U, and V samples and the final RGBA presentation.

Selectable compound and inter-intra fixtures

The four selectable-compound fixtures use the same pinned tests/data/webp_logo_animated.y4m source and its 0872208D9C19B68B10A1647FA6849CFC4E2B21A19561ACD672E0629C70EFACA2 SHA-256. They were encoded at speed zero after disabling later inter-mode checkpoints. Each command also disables competing prediction tools that would prevent the resulting stream from isolating its named mode:

./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-masked-comp=0 -a enable-interintra-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-distance-weighted-compound.avif
./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-dist-wtd-comp=0 -a enable-diff-wtd-comp=0 -a enable-interintra-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-wedge-compound.avif
./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-dist-wtd-comp=0 -a enable-interinter-wedge=0 -a enable-interintra-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-difference-weighted-compound.avif
./avifenc -j 1 -c aom -s 0 -q 80 -a enable-obmc=0 -a enable-warped-motion=0 -a enable-global-motion=0 -a enable-dist-wtd-comp=0 -a enable-masked-comp=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-inter-intra.avif

Pinned scalar libavif generated each final native and presentation reference with:

./avifdec -j 1 -c aom --index 18 <fixture>.avif <fixture>-libaom.y4m
./avifdec -j 1 -c aom --index 18 <fixture>.avif <fixture>-libavif.png
Fixture AVIF SHA-256 Frame-18 Y4M SHA-256 Frame-18 PNG SHA-256
libavif-webp-logo-distance-weighted-compound DA710D11C60F03EEA209E4360E2FC807B89C49AD50671F0DFB1BCF4AD5EF76DD 904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97 D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C
libavif-webp-logo-wedge-compound 98640640A445055FEA3D9E2F4A78FEEF54E97F8171B472CF57D99156E1C553B2 904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97 D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C
libavif-webp-logo-difference-weighted-compound FC6459CD334762D74D9D2654640221E80C463CC01B82B29A5866C9E725ABE273 904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97 D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C
libavif-webp-logo-inter-intra 71DF22E63626B5BC9001FF1E88076B90F11BB47D18089750853E66F0CBBB084B 502265688138641A7B12C8C4190B66C76CD4808D9AED05B06486056B39D7E9A0 F0DE4CCDFB6D95A400E69B69FA4C57F0BEEEEE75825722C31613385F0B3FD9FC

Pinned libaom block tracing confirms that these streams select distance weighting, both wedge signs, both difference-mask types, and both smooth and wedge inter-intra prediction. The production test independently requires those decoded mode states, decodes all preceding samples, compares the final native Y, U, and V planes exactly, compares the final RGBA presentation exactly, and repeats reconstruction with constrained tracked allocation.

Overlapping motion-compensation fixture

The libavif-webp-logo-obmc.avif fixture uses the same pinned tests/data/webp_logo_animated.y4m source and source SHA-256 as the compound fixtures. It was encoded with the pinned scalar toolchain after disabling competing compound, inter-intra, warped, and global prediction modes:

./avifenc -j 1 -c aom -s 0 -q 80 -a max-reference-frames=3 -a enable-dist-wtd-comp=0 -a enable-masked-comp=0 -a enable-interintra-comp=0 -a enable-warped-motion=0 -a enable-global-motion=0 tests/data/webp_logo_animated.y4m libavif-webp-logo-obmc.avif

Pinned scalar libavif generated the final native and presentation references with:

./avifdec -j 1 -c aom --index 18 libavif-webp-logo-obmc.avif libavif-webp-logo-obmc-libaom.y4m
./avifdec -j 1 -c aom --index 18 libavif-webp-logo-obmc.avif libavif-webp-logo-obmc-libavif.png

The AVIF SHA-256 is 765245F71BD398F7AD87BD83FD5C5C11172981B37A4FABF4F10F65D4E8AEA537. The retained frame-18 Y4M SHA-256 is 904D1B5B3E7F334CE8D44040F9A7BDCAC1F7773122FF1C5F06A5B4DD31A62A97, and the frame-18 PNG SHA-256 is D2CB388C9092EF17C4F0382C0150DD30D6F9D0EE247FF45AB5D7D4D312CEB23C. Pinned libaom block tracing records more than one hundred actual OBMC blocks across the decoded sequence, including blocks with nonzero horizontal and vertical motion vectors. The production test requires decoded OBMC mode state, decodes every retained-reference dependency, compares the final native Y, U, and V planes exactly, compares the final RGBA presentation exactly through FeatureTestRunner, and repeats reconstruction with constrained tracked allocation. Direct production-branch tests separately cover 8/10/12-bit storage and 4:2:0 and 4:2:2 overlap geometry.

Local warped-motion fixture

The libavif-rotating-grid-local-warp.avif fixture was encoded from a deterministic two-frame 256x256 limited-range YUV444 source. The source combines checkerboard, ring, and chroma-gradient detail; its second frame rotates the first by 2.5 degrees with nearest-neighbor sampling and edge clamping. The two-frame source Y4M SHA-256 is 82C1468C95C996B05165590417184F59373D67896F8C7B0EB398582C29C9C7A7. Pinned scalar libavif and libaom generated the fixture and references with:

./avifenc -j 1 -s 0 -q 60 -a color:enable-warped-motion=1 -a color:enable-global-motion=0 -a color:enable-obmc=0 rotating-grid-256-two-frame.y4m libavif-rotating-grid-local-warp.avif
./avifdec -j 1 --index 1 libavif-rotating-grid-local-warp.avif libavif-rotating-grid-local-warp-libaom.y4m
./avifdec -j 1 --index 1 libavif-rotating-grid-local-warp.avif libavif-rotating-grid-local-warp-libavif.png

The AVIF SHA-256 is 990BAC4AD443005C217B0DA4FCCFA9ADFB3AA147AD06C85F9A655A4433E9E8A7. The retained frame-1 Y4M SHA-256 is 984B2815CEE0C05FDE26430F150A21B5C993141E25BA1ED4FDE09372DB64AC13, and the frame-1 PNG SHA-256 is 4490D62FB6679378E92CACA48427359091AD2106BE49FC1A3848F78BE03BEEB1. Pinned libaom tracing records many actual WARPED_CAUSAL blocks. The multi-sample model at mode-information row 6, column 8 derives matrix [-191565, 599107, 61755, -140, -6909, 62012] and reduced shear [-3776, -128, -7360, -3520] from four retained neighbor samples. The production test requires decoded warped mode state, compares every final native Y, U, and V sample and the final RGBA presentation exactly, runs normal and scalar dispatch through FeatureTestRunner, and repeats reconstruction with constrained tracked allocation.

Global warped-motion fixture

The libavif-rotating-grid-global-warp.avif fixture uses the same deterministic two-frame 256x256 limited-range YUV444 source and its 82C1468C95C996B05165590417184F59373D67896F8C7B0EB398582C29C9C7A7 SHA-256. Pinned libavif commit 062e582e8afda88e6baf988fdcf046a801efa0f5 and libaom commit 03087864cf4bea6abb0d28f95cf7843511413d8f generated the fixture and references with:

./avifenc -j 1 -s 0 -q 100 -a color:enable-warped-motion=0 -a color:enable-global-motion=1 -a color:enable-obmc=0 rotating-grid-256-two-frame.y4m libavif-rotating-grid-global-warp.avif
./avifdec -j 1 --index 1 libavif-rotating-grid-global-warp.avif libavif-rotating-grid-global-warp-libaom.y4m
./avifdec -j 1 --index 1 libavif-rotating-grid-global-warp.avif libavif-rotating-grid-global-warp-libavif.png

The AVIF SHA-256 is EE8CDF6DF36FB2999A17D2A86C41040D8BE13B958A1D5AE53E37343C6FB49E0E. The retained frame-1 Y4M SHA-256 is A36D445778BB2D37D69526A1058E3569DA24F3913317EFE22ADB61748A0F7511, and the frame-1 PNG SHA-256 is F7D27ABF79450DFA311F72106FD1DA80997EABC0937F2F5578EF627119FF83B0. Pinned libaom tracing records seven actual GLOBALMV blocks using the valid rotation/zoom matrix [-357376, 372736, 65468, 2856, -2856, 65468] and reduced shear [-64, 2880, -2880, 64]. The production sequence test requires that decoded model and mode state, compares every final native Y, U, and V sample and the final RGBA presentation exactly, runs normal and scalar dispatch through FeatureTestRunner, and repeats reconstruction with constrained tracked allocation. A direct production-branch test independently drives both references of GLOBAL_GLOBALMV through the matrix predictor and compound averaging at 8, 10, and 12 bits.

Updating fixtures

Do not create conformance references with ImageSharp. Generate both the native-plane and presentation references with an independent decoder, record the exact upstream revisions and source license, and preserve exact comparisons. A new tool-specific fixture should demonstrate that the relevant syntax is active and should be no larger than required to cover that behavior.