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ffmpeg patterns for video pipelines — filters, audio, concat, GIF generation, codec settings. Covers Ken Burns, letterbox, fade, multi-act assembly, and macOS gotchas.
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基于 SOC 职业分类
Python CLI patterns — typer apps, uv with PEP 723 inline deps, pytest, pathlib, atomic file writes, file locking, JSONL streaming, and production-grade stdlib idioms for command-line tools
Commanded CQRS/event-sourcing patterns for aggregates, commands, events, process managers, projections, and event handlers
Phoenix LiveView patterns for stateful server-rendered UI including streams, async assigns, components, forms, uploads, and JS hooks
Oban background job patterns — workers, queues, scheduling, unique jobs, retries, telemetry, engines, and Oban Pro features (Workflow, Batch)
Elixir testing patterns — ExUnit organization, ExMachina factories, Mox boundary mocking, Bypass HTTP stubbing, parameterize, sandbox patterns, and async-safe concurrency
Ecto database patterns — schemas, changesets, query composition, Multi transactions, migrations, ParameterizedType, UUIDv7, and performance tuning
| name | ffmpeg-expert |
| description | ffmpeg patterns for video pipelines — filters, audio, concat, GIF generation, codec settings. Covers Ken Burns, letterbox, fade, multi-act assembly, and macOS gotchas. |
inputs (-i) → [filter graph: -vf / -af / -filter_complex] → codec flags → output
, — applied in order; and [labels] — for complex graphs (split, overlay, amix)-an strips audio output; -vn strips video output-map 0:v:0 -map 1:a:0 — explicit stream selection when merging inputs| I need to... | Use |
|---|---|
| Photo → video with Ken Burns zoom | → references/filters.md |
| Letterbox any source to 1920×1080 | → references/filters.md |
| Fade video in/out | → references/filters.md |
| Normalize fps + SAR before concat | → references/filters.md |
| Loop a short song over a longer video | → references/audio.md |
| Fade audio in/out | → references/audio.md |
| Merge separate video + audio files | → references/audio.md |
| Fix silent audio after concat | → references/audio.md (sample rate) |
| Join pre-built segments | → references/pipeline-patterns.md |
| Multi-act pipeline with per-act music | → references/pipeline-patterns.md |
| Extract a frame from video | → references/pipeline-patterns.md |
| Create a quality GIF | → references/gif.md |
| Boomerang / speed-ramped GIF | → references/gif.md |
| Issue | Fix |
|---|---|
bc aliased | Use /usr/bin/bc explicitly |
BSD date rejects GNU flags | date -j -f '%Y-%m-%d' "YYYY-MM-DD" '+%B %Y' |
| HEIC not recognized | brew install libheif |
| Glob matches nothing → literal string passed | shopt -s nullglob at script top |
fade=t=out:st= uses scientific notation | printf '%.6f' $(echo "$d - $f" | /usr/bin/bc) |
| Audio silent after concat | Mismatched sample rates — add -ar 48000 to all audio prep |
| DTS errors in concat | Mixed fps or SAR — normalize before joining |
ffmpeg 8: -framerate on concat removed | Use duration directive in list file instead |
| Zoompan pixelates at zoom | Render at 2× resolution, downscale after (see filters.md) |
-c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p # archival quality
-c:v libx264 -crf 26 -preset medium # shareable / preview
-c:a aac -b:a 192k -ar 48000 # audio (always set -ar)
-movflags +faststart # web streaming
CRF scale: 0 = lossless, 18 = high quality, 23 = default, 28 = small file, 51 = worst.
ffprobe -v quiet -show_entries format=duration -of csv=p=0 "$file"
# returns float seconds, e.g. 12.345678
references/filters.md — Ken Burns/zoompan, letterbox, fade, fps/SAR normalization, drawtextreferences/audio.md — stream_loop, afade, sample rate, audio merge patternsreferences/pipeline-patterns.md — concat demuxer, photo→video, multi-act assemblyreferences/gif.md — two-pass palette, boomerang, speed, size optimization