feat(vmaf-tune): ADR-0498 follow-up #7 — encoder stats, x264 detection, backend dispatch, codec-list parser

[lusoris]

Summary

• Sub-task 1 (x264/x265/libvpx detection): extend _VERSION_PROBE_PATTERNS to cover libx265 and libvpx-vp9 in addition to the existing entries; add EncoderInfo dataclass (encoder, codec_detected: bool, version_label: str) and probe_encoder_info() public helper so callers check codec_detected instead of parsing the version string.
• Sub-task 2 (stats-file regression): remove duplicate fallback_duration assignment in build_pass1_stats_command (dead first write left by the fix(build): stop VMAF_VERSION degrading to a bare commit abbreviation #1266 refactor; second identical assignment overwrote it immediately).
• Sub-task 3 (backend dispatch): add backend kwarg to _build_production_sample_extractor and forward it to run_score; _build_prod_predictor and fast_recommend forward the backend selected by score_backend.select_backend so all 30 TPE probe-encode trials score on GPU when available. Remove dead _ = backend stub from _gpu_verify.
• Sub-task 4 (codec-list parser): implement codec_adapters.parse_available_codecs(stdout, *, restrict_to_known=True) that parses ffmpeg -hide_banner -encoders into a frozenset of available codec names.

Test plan

• pytest tools/vmaf-tune/tests/test_adr_0498_followup7.py — 16 new tests, all pass.
• pytest tools/vmaf-tune/tests/test_encoder_stats_capture_x264.py — existing stats-capture tests still pass.
• pytest tools/vmaf-tune/tests/test_bbb_e2e_v2_bug_cluster.py — existing probe-cache tests still pass.
• pytest tools/vmaf-tune/tests/test_encode_dispatcher_per_adapter.py — all pass after fix to capture first subprocess call only.
• pytest tools/vmaf-tune/tests/test_fast.py — all pass.
• Full suite: 1499 passed, 16 skipped, 2 xfailed (pre-existing test_format_both_json.py failure unrelated to this PR).

Reproducer / smoke test

# Sub-task 1
python -c "from vmaftune.encode import probe_encoder_info; print(probe_encoder_info.__doc__)"

# Sub-task 4
python -c "from vmaftune.codec_adapters import parse_available_codecs; print(parse_available_codecs.__doc__)"

# All tests
pytest tools/vmaf-tune/tests/test_adr_0498_followup7.py -v

ADR-0108 deliverables checklist

• Research digest: no digest needed: trivial (all four sub-tasks are bug fixes / follow-up implementations with one obvious approach each)
• Decision matrix: no alternatives: only-one-way fix (duplicate assignment removal, probe pattern extension, backend kwarg forwarding, codec-list parser are all single-path implementations)
• AGENTS.md invariant note: tools/vmaf-tune/AGENTS.md updated with probe-cache expansion, backend kwarg, and codec-list parser invariants
• Reproducer / smoke-test command: see Test plan above
• Changelog fragment: changelog.d/fixed/0498-vmaf-tune-adr-0498-followup7.md
• Rebase-notes entry: docs/rebase-notes.md — no rebase impact (all changes fork-local to tools/vmaf-tune/)

State.md

No bugs opened or closed by this PR; no state.md update required.

ffmpeg-patches

No public C-API surfaces, CLI flags, or meson_options.txt entries touched; no patch update required.

Semgrep note

The semgrep-local hook was skipped via SKIP=semgrep-local due to a pre-existing io_uring_queue_init memory allocation failure in the dev environment (documented in .pre-commit-config.yaml lines 241-275 as a known system RLIMIT_MEMLOCK issue). Manual verification via python -m semgrep --config .semgrep.yml --error --quiet --jobs 1 <files> returns exit 0 on all changed files.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR is a vmaf-tune follow-up for ADR-0498 that tightens encoder capability probing, fixes a pass-1 stats command regression, ensures fast-path proxy trials score on the selected libvmaf backend, and adds an ffmpeg encoder-list parser to gate codec-specific behavior on runtime availability.

Changes:

• Add structured encoder probe results (EncoderInfo + probe_encoder_info) and extend _VERSION_PROBE_PATTERNS to include libx265 and libvpx-vp9.
• Forward the selected scoring backend through the fast-path production sample extractor so TPE probe trials can score on GPU backends when available.
• Introduce codec_adapters.parse_available_codecs() to parse ffmpeg -hide_banner -encoders output into an available-codec set, and add regression tests.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tools/vmaf-tune/src/vmaftune/encode.py	Extends encoder configure-flag probing and adds EncoderInfo + probe_encoder_info; removes duplicate fallback_duration assignment.
tools/vmaf-tune/src/vmaftune/fast.py	Threads a backend kwarg into the production sample extractor and forwards it to run_score.
tools/vmaf-tune/src/vmaftune/codec_adapters/init.py	Adds parse_available_codecs() and updates codec stats-support documentation.
tools/vmaf-tune/tests/test_encode_dispatcher_per_adapter.py	Stabilizes subprocess argv capture by ignoring the follow-up ffmpeg -version probe call.
tools/vmaf-tune/tests/test_adr_0498_followup7.py	Adds regression coverage for all four sub-tasks (encoder probe, stats command, backend forwarding, codec parser).
tools/vmaf-tune/AGENTS.md	Documents new invariants for probing, backend forwarding, and codec parsing.
docs/rebase-notes.md	Records fork-local rebase impact notes for this feature.
changelog.d/fixed/0498-vmaf-tune-adr-0498-followup7.md	Adds changelog entry for the fixes and new helper/parser.

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