magnus919_agent-skills/ffmpeg/references/local-verification.md

Local Verification Dossier

Access/test date: 2026-09-01 Host: macOS Binary: Homebrew-installed ffmpeg Version: FFmpeg 8.1.2, libavutil 60.26.102, libavcodec 62.28.102 Build evidence: ffmpeg -version reports --enable-videotoolbox, --enable-audiotoolbox, libx264, libx265, libsvtav1, libvmaf, libopus, libmp3lame, libdav1d, and libvpx.

Inventory

The local build reported 488 filters, 201 encoders, and 2 hardware acceleration methods in the captured inventories. The exact lists are preserved in local-filters.txt, local-encoders.txt, and local-hwaccels.txt. Availability is build-specific: never assume a filter, encoder, protocol, or hardware backend exists just because an online example uses it.

Successful experiment

A synthetic 320x180, 30 fps test video and 48 kHz mono sine-wave audio were generated with lavfi and encoded to MP4 using libx264 and native AAC. ffprobe verified a 2.00-second MP4 containing H.264 video and AAC audio. The source log is ../03-dossiers/local-probe.json and the command output is recorded in the run log outside this dossier.

The intended follow-up transcode used -ss 0.5 -t 0.75, scaling to 160 pixels wide, reducing to 15 fps, and adding drawtext. It failed before writing output because this local build reported No such filter: 'drawtext'. This is useful evidence: filter names and compiled capabilities must be checked with ffmpeg -filters or ffmpeg -h filter=<name> before placing them in automation. The failed and successful run logs were preserved in the local study record; their host-specific paths are intentionally omitted here.

Verification lesson

A command that looks portable can still fail at the filter-availability boundary. The correct response is not to silently substitute a different filter or claim success. Inspect the local build, choose an available equivalent, or install/use a build with the required feature, then rerun and probe the resulting media.

Reproduction commands

ffmpeg -version
ffmpeg -filters
ffmpeg -encoders
ffmpeg -hwaccels
ffprobe -v error -show_format -show_streams -of json input.mp4

SOURCES (LAYER 3 NAVIGATION) https://ffmpeg.org/ffprobe.html -> Official description of machine-readable media inspection.

https://ffmpeg.org/ffmpeg.html -> Official command-line processing model and option semantics.