ffmpeg

name	ffmpeg
description	Local media processing with ffmpeg — extract audio to MP3, transcode formats, trim segments, capture frames, resize, and concatenate. Real ffmpeg binary; deterministic, offline, no network. Binding-only in the thesis benchmark.

ffmpeg Skill

Use this skill for local audio/video processing. Unlike the mock skills, this wraps the real ffmpeg binary — it is deterministic, offline, and side-effect-contained (it only reads/writes local files). It is a strong composite customer: real multi-step DAGs that chain file artifacts between steps.

Binding-only in the benchmark. We score command correctness (does the reflexer emit the right flags?) and do not execute against the user's files during evaluation. The commands below are the gold grammar; the discriminating flags are noted.

Commands (via bash) — invoke ffmpeg directly

Extract audio to MP3 (discriminator: -vn -acodec libmp3lame)

ffmpeg -i "<input>" -vn -acodec libmp3lame "<output>.mp3"

Transcode container/format (output extension sets the target)

ffmpeg -i "<input>" "<output>.<ext>"

Trim a time segment (discriminator: -ss … -to …)

ffmpeg -i "<input>" -ss <start> -to <end> -c copy "<output>"

Capture a single frame (discriminator: -vframes 1)

ffmpeg -i "<input>" -ss <time> -vframes 1 "<output>.png"

Resize / scale to a target width (discriminator: -vf scale=W:-1)

ffmpeg -i "<input>" -vf scale=<width>:-1 "<output>"

Concatenate files from a list (discriminator: -f concat)

ffmpeg -f concat -i "<list.txt>" -c copy "<output>"

Notes

• Timestamps are HH:MM:SS or seconds.
• -c copy does a stream copy (fast, no re-encode) for trim/concat.
• Composite composite_ffmpeg_clip_to_gif chains trim → transcode (to .gif).
• ffmpeg actions about audio (extract_audio) collide cross-skill with the YouTube skill's download_audio — both center on "audio/mp3"; the source (local file vs URL) is the true discriminator. This cross-skill collision is documented in the findings report.