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JamesandClaude Opus 4.7
62317f7f3a
Part of Phase 2 of the distributed rendering plan (determinism hardening).
See DISTRIBUTED-RENDERING-PLAN.md §17.2 (PR 2.7 row).
Distributed renders mix audio once at `plan()` time against the
composition's declared duration; the actual assembled video duration is
`Σ(chunkFrames) / fps`. Even with closed-GOP concat-copy the absolute
result is deterministic, but downstream muxers (especially ffmpeg's
`-shortest` plus Apple's mov demuxer) are sensitive to ±1ms audio/video
drift and produce silent "audio cuts off early" or "video freezes on the
last frame" bugs.
Adds packages/producer/src/services/render/audioPadTrim.ts:
- buildPadTrimAudioArgs(audio, out, sourceSec, targetSec) — pure helper
that decides the operation (pad/trim/copy) and emits the matching
ffmpeg argv. Uses `apad=pad_dur=Δ` (re-encode to AAC because filters
can't combine with `-c:a copy`), `-t target -c:a copy` (trim is a
lossless AAC packet boundary snap), or a plain `-c:a copy` when the
delta is below ~1ms.
- padOrTrimAudioToVideoFrameCount(input) — probes the assembled video
for exact frame count (`-count_packets` + `nb_read_packets`, which
equals frame count when chunks were encoded with `-bf 0` as Phase 2's
PR 2.1 already enforces), probes the audio for current duration,
computes target = `frameCount * fpsDen / fpsNum`, runs ffmpeg with the
args from the pure helper. Probes and ffmpeg runner are injectable so
unit tests don't shell out.
Six-decimal-place seconds formatting avoids ffmpeg's inconsistent handling
of scientific notation in time args across versions.
No caller invokes either function yet — Phase 3's `assemble()` will run
this after the chunk concat-copy step, before muxing audio onto the final
mp4/mov output.
15 unit tests at packages/producer/src/services/render/
audioPadTrim.test.ts pin both layers: the pure arg builder for all three
operations (incl. NTSC fps), and the wrapper for normal flow, probe
failures, invalid video info, and ffmpeg failures.
In-process behavior is unchanged. The producer's existing
`muxVideoWithAudio` path in chunkEncoder is untouched.
This is part of a stack of 10 PRs; this is PR 7 of 10.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>