[Project516]

What and why

Aborting the AbortSignal passed to exec() only rejected the promise. The command kept running in the worker and blocked every later call. Now, where SharedArrayBuffer is usable (cross-origin isolated pages, always on Node.js), exec() shares a 4-byte Int32Array with the worker per call and the abort sets it. The core polls it at the same place it polls the timeout, so the command stops like a timeout does.

• Exit code: 1, the same as a timeout. The promise has already rejected with AbortError by then, so callers do not see it.
• Without SharedArrayBuffer (st core on a non-isolated page): unchanged, the abort only rejects the promise. Documented in the exec() doc comment, usage docs and CHANGELOG.
• ffprobe() is unchanged: the patched fftools has no timeout check for it either.
• No fftools patch change. bind.js makes Module.timeout an accessor: a set flag reads as 0 (timed out), and a flag with no timeout reads as a huge value so ffmpeg takes the existing 5 ms polling path instead of the 500 ms report period. Setting a real timeout works as before.
• The flag is created per call, so aborting one call cannot stop another.

Upstream: ffmpegwasm#978.

Tests

Browser suite (skipped unless crossOriginIsolated) and Node suite (st and mt): start -re -f lavfi -i testsrc ... -f null -, which never ends alone, wait for its first Output #0 log line, abort, assert AbortError, then assert a following exec() returns 0 within 10 s. Without the fix the follow-up call never returns.

Not run locally

Needs a rebuilt core (bind.js is linked into it), which only CI builds. pnpm lint and a type check ran locally; the Module.timeout accessor was exercised in plain Node.

Noticed, not fixed

• A signal that is already aborted when exec() is called does not reject or stop anything, because the abort event never fires. This was already the case.
• An aborted call that was still queued behind another call runs when its turn comes; with the flag set it stops at the first check, but it is not skipped.
• The browser suite is skipped for the st core unless the test page is cross-origin isolated; the Node suite covers both cores.

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Reviewing files that changed from the base of the PR and between c8e356d and ac5aa24.

📒 Files selected for processing (10)

• CHANGELOG.md
• apps/website/docs/getting-started/usage.md
• packages/ffmpeg/src/classes.ts
• packages/ffmpeg/src/types.ts
• packages/ffmpeg/src/worker-node-entry.mts
• packages/ffmpeg/src/worker.ts
• packages/types/types/index.d.ts
• src/bind/ffmpeg/bind.js
• tests/ffmpeg-node.test.mjs
• tests/ffmpeg.test.js

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[project516-review-bot]

This PR adds support for stopping a running exec() command when an AbortSignal fires, using a SharedArrayBuffer-backed flag polled by the ffmpeg core. The abort flag is created per call and only used when SharedArrayBuffer is available (cross-origin isolated pages and Node.js); otherwise the abort only rejects the promise. The implementation modifies the Module.timeout accessor in bind.js to return 0 when the flag is set, causing the command to exit like a timeout.

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_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}