marfrit
5a085e7180
Targets the one H.264 kernel most likely to be QPU-worthy: in-loop deblock. Cycles 6 and 7 (IDCT 4x4 and 8x8) both came in CPU-only because H.264 transforms are NEON-trivial. H.264 deblock has analogous structure to VP9 LPF (cycles 2+4, both GREEN) so predicted R8 = ORANGE/YELLOW. This commit: - Vendors ff_h264_*_loop_filter_*_neon from h264dsp_neon.S (1076 lines, includes both v/h luma + chroma + intra variants + weight/biweight) - PROVENANCE.md updated with the new vendored file - Phase 1 doc captures the full plan: start with luma vertical non-intra (most common case), defer Phase 3+ to next session H.264 deblock C ref scope is ~2 hours (per-row branching, per-4-row-segment tc0, ap/aq side conditions, alpha/beta thresholds — much more complex than VP9 LPF wd=4's single-branch filter). Deferring to fresh attention next session rather than rushing now. After cycle 8 closes, the H.264 QPU surface is well-characterised and the cycles-1-8 inventory drives the Phase 8 V4L2 wrapper's substrate-routing recipe. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
98 lines
4.5 KiB
Markdown
98 lines
4.5 KiB
Markdown
# FFmpeg source snapshot
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Verbatim subset of FFmpeg source pinned for use as reference
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implementations of the VP9 8×8 inverse DCT (Phase 1 target of
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`daedalus-fourier`). See `../../docs/phase2.md §2` and `§5` for
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the rationale.
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## Upstream pin
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- **Repository**: https://github.com/FFmpeg/FFmpeg
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- **Tag**: `n7.1.3` (matches `libavcodec61 8:7.1.3-0+deb13u1+rpt1`
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shipping in Debian Trixie on the dev host `hertz`)
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- **Annotated tag object**: `0a9a757e96fdf053697084bbd1f620edeac9d084`
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- **Commit object (tag target)**: `f46e514491172d15bd74b4abb1814cd2f05a763e`
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- **Snapshot fetched**: 2026-05-18 (UTC), via
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`https://raw.githubusercontent.com/FFmpeg/FFmpeg/n7.1.3/<path>`
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## Files in this snapshot
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All files are byte-for-byte copies of the upstream source at the
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tagged commit, no modifications.
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| Path | Lines | Bytes | SHA-256 |
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|---|---|---|---|
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| `libavcodec/vp9dsp_template.c` | 2578 | 89045 | `41b21f667a6c497b620aa1637d8269badc45d1ac7e621d694441c5bf39356e4f` |
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| `libavcodec/aarch64/vp9itxfm_neon.S` | 1580 | 63534 | `82ee3ceed4735c63576bafdcee28e2215652743ade55a9eab46a16d9530369f6` |
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| `libavcodec/aarch64/vp9lpf_neon.S` | 1334 | — | `384e49e7a6e838d9e38aedc00838ed4aebfa6c5bdb343ecaf23ef639bc10fbb7` |
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| `libavcodec/aarch64/vp9mc_neon.S` | 665 | — | `6b1d50f9821742584fdd47758057f810644aff3a008faaa774ff5b9cac4d1fef` |
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| `libavcodec/aarch64/h264idct_neon.S` | 415 | 16269 | `963ffe5f31b5a6a422e13b0d394cf5630126927abfb23aa214f7cbe83d60683f` — H.264 IDCT 4×4/8×8/DC NEON kernels for cycle 6+ |
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| `libavcodec/aarch64/h264dsp_neon.S` | 1076 | — | `978e076f0020e688b40c6dd827708c3d53e17c64a99fd0052e43d983536ce638` — H.264 in-loop deblock + weight/biweight kernels for cycle 8+ |
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| `libavcodec/vp9_subpel_filters_table.c` | — | — | hand-extracted from `libavcodec/vp9dsp.c` at same n7.1.3 pin — provides `ff_vp9_subpel_filters` for `vp9mc_neon.S` to link against without dragging in vp9dsp.c's full init machinery |
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| `libavcodec/aarch64/neon.S` | 173 | 7496 | `72d36ce6c3fcc5e53de869cfe10fda16225ebe580c32891bccc240a30a85a538` |
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| `libavutil/aarch64/asm.S` | 260 | 8069 | `c0d03143b1bc5a9e358222d08d2d449d595271844fe7a3dc23bffb91abe8b0e3` |
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| `COPYING.LGPLv2.1` | 502 | — | `b634ab5640e258563c536e658cad87080553df6f34f62269a21d554844e58bfe` |
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Verify with:
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```sh
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( cd external/ffmpeg-snapshot && sha256sum -c <<'EOF'
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41b21f667a6c497b620aa1637d8269badc45d1ac7e621d694441c5bf39356e4f libavcodec/vp9dsp_template.c
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82ee3ceed4735c63576bafdcee28e2215652743ade55a9eab46a16d9530369f6 libavcodec/aarch64/vp9itxfm_neon.S
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72d36ce6c3fcc5e53de869cfe10fda16225ebe580c32891bccc240a30a85a538 libavcodec/aarch64/neon.S
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c0d03143b1bc5a9e358222d08d2d449d595271844fe7a3dc23bffb91abe8b0e3 libavutil/aarch64/asm.S
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b634ab5640e258563c536e658cad87080553df6f34f62269a21d554844e58bfe COPYING.LGPLv2.1
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EOF
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)
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```
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## License
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LGPL-2.1-or-later. See `COPYING.LGPLv2.1`. Original copyright
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holders include the FFmpeg authors and Google Inc. (2016) for
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the aarch64 NEON paths. The snapshot inherits FFmpeg's license
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in full.
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## Why each file is in this snapshot
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- `libavcodec/vp9dsp_template.c` — contains `idct_idct_8x8_add_c`,
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the bit-exact C reference for the Phase 1 kernel under test (M1).
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- `libavcodec/aarch64/vp9itxfm_neon.S` — contains
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`ff_vp9_idct_idct_8x8_add_neon`, the NEON throughput baseline
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(M3). Also defines `idct8`, `dmbutterfly0`, `dmbutterfly`,
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`dmbutterfly_l`, `butterfly_8h`, and the `idct_coeffs` constant
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table.
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- `libavcodec/aarch64/neon.S` — defines `transpose_8x8H` used by
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`vp9itxfm_neon.S`.
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- `libavutil/aarch64/asm.S` — defines `function`, `endfunc`,
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`movrel`, `const`, `endconst`, and other assembly preamble
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macros required to assemble the above NEON files.
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## Re-vendoring procedure
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If the upstream pin needs to change (e.g., hertz updates to a
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newer libavcodec):
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```sh
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TAG=nX.Y.Z
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BASE=https://raw.githubusercontent.com/FFmpeg/FFmpeg/$TAG
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cd external/ffmpeg-snapshot
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for f in libavcodec/vp9dsp_template.c \
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libavcodec/aarch64/vp9itxfm_neon.S \
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libavcodec/aarch64/neon.S \
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libavutil/aarch64/asm.S \
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COPYING.LGPLv2.1; do
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curl -sSf -o "$f" "$BASE/$f"
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done
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sha256sum libavcodec/vp9dsp_template.c \
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libavcodec/aarch64/vp9itxfm_neon.S \
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libavcodec/aarch64/neon.S \
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libavutil/aarch64/asm.S \
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COPYING.LGPLv2.1
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# update this PROVENANCE.md with the new tag, commit hash, and hashes
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```
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After re-vendoring, re-run the bit-exact gate (M1) and throughput
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baseline (M3) — both can shift across FFmpeg versions even when
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the VP9 spec doesn't change (e.g., NEON micro-optimizations).
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