feat(node): ffmpeg latest pinned + ffmpeg-patches bundled into Dockerfile

[lusoris]

Summary

• Phase 4b.4 (ADR-0709): ships docker/Dockerfile.node with four targets (node-cpu, node-cuda, node-rocm, node-sycl), each carrying ffmpeg n8.2 compiled from source with all 15 ffmpeg-patches/ patches applied.
• Adds cmd/vmafx-node Go binary with startup encoder-inventory probe (ffmpeg -encoders cache) and gRPC server scaffold (full gRPC wiring is Phase 4b.5).
• FFmpeg version policy (ADR-0717): pin to latest stable tagged release (n8.2); update FFMPEG_TAG on each release-sync PR.

What's included

docker/Dockerfile.node

Multi-stage build:

1. vmaf-builder — libvmaf.so + vmaf CLI from core/ (CPU, release/stripped)
2. ffmpeg-deps-base — codec build deps + SVT-AV1 from source (Ubuntu's libsvtav1-dev omits SvtAv1Enc.pc)
3. ffmpeg-builder-cpu — ffmpeg n8.2, patches applied, configured with --enable-libvmaf --enable-libx264 --enable-libx265 --enable-libvpx --enable-libsvtav1 --enable-libdav1d
4. go-builder — cmd/vmafx-node binary
5. runtime-base — distroless cc-debian12
   6–9. node-cpu / node-cuda / node-rocm / node-sycl — final targets

libaom excluded: ffmpeg-patches/0007 references aom_roi_map_t fields not present in any released libaom. SVT-AV1 is the production AV1 lane.

cmd/vmafx-node

• main.go — discovers VMAFX_FFMPEG_BIN, runs startup probe, starts server
• probe/probe.go + probe_test.go — ffmpeg -encoders inventory cache
• server/server.go + server_test.go — gRPC server scaffold (Phase 4b.5 wiring deferred)

Documentation / deliverables

• docs/adr/0717-vmafx-node-ffmpeg-latest.md — version policy decision record
• docs/development/vmafx-node.md — operator guide (image variants, codec matrix, env vars, smoke tests)
• changelog.d/added/node-ffmpeg-latest.md — release fragment
• docs/adr/README.md — index rows for ADR-0710/0711/0712/0717
• docs/state.md — recently-closed row for Phase 4b.4
• docs/rebase-notes.md — ffmpeg base bump procedure for future syncs

Smoke test

# Build CPU variant
docker buildx build --target node-cpu -f docker/Dockerfile.node -t vmafx-node:test .

# Verify ffmpeg version
docker run --rm vmafx-node:test ffmpeg -version | head -1
# → ffmpeg version n8.2 ...

# Verify codec inventory
docker run --rm vmafx-node:test ffmpeg -hide_banner -encoders 2>/dev/null \
  | grep -E 'libx264|libx265|libsvtav1|libvpx'

# Netflix golden score (mount test fixtures)
docker run --rm -v "$PWD/python/test/resource:/data:ro" vmafx-node:test \
  /usr/local/bin/vmaf \
    --reference /data/yuv/src01_hrc00_576x324.yuv \
    --distorted  /data/yuv/src01_hrc01_576x324.yuv \
    --width 576 --height 324 --pixel_format 420 --bitdepth 8
# Expected VMAF score: ~76.668 (Netflix golden)

Deliverables checklist

• Research digest: no digest needed: trivial — version pin + Dockerfile pattern established by dev/Containerfile
• Decision matrix: ADR-0717 §Alternatives considered (tag vs rolling vs dev-container vs distro)
• AGENTS.md invariant: no rebase-sensitive invariants — docker/Dockerfile.node is fork-local, no upstream overlap
• Reproducer / smoke-test command: in PR description above
• changelog.d/added/node-ffmpeg-latest.md
• docs/rebase-notes.md entry: ffmpeg base bump procedure added

ADR

ADR-0717 — parent: ADR-0709 Phase 4b item 4b.4.

Notes for reviewers

• The go.sum checksum mismatch on golang.org/x/sync is pre-existing (not introduced by this PR). Verify with git diff master -- go.sum.
• NVENC / QSV / AMF encoders in node-cuda / node-sycl / node-rocm require the host's GPU driver at runtime; the probe logs WARN for absent HW encoders but does not block startup.
• A CI job validating patches against n8.2 specifically is tracked as follow-up; the Dockerfile itself serves as the build-time gate.

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