What is ffmpeg-mixing?

Guidance for using ffmpeg to trim, mix, and join video clips while keeping their sound and picture synchronized. ffmpeg is a command-line tool for processing media files.

Stitching generated clips into a video, inserting scenes at exact times, and building ffmpeg filter graphs with continuous audio.

It avoids timing drift caused by trimming an input twice with conflicting timestamp systems.

How vargHQ/sdk configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to vargHQ/sdk. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/vargHQ/sdk/main/.claude/skills/ffmpeg-mixing/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/vargHQ/sdk

Made for: Claude Code.

Wrote this? Show the measurements

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README.md

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Your own site · 80×15

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Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 825 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00054	$0.00825
Opus 5.5	$0.00022	$0.00330
Sonnet 5.5	$0.00011	$0.00165
Haiku 4.5	$0.00005	$0.00082

Measured 2mo ago against content hash 03f742a522a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

ffmpeg-mixing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/ffmpeg-mixing/SKILL.md · 82 lines

How it starts

The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ffmpeg video mixing

Lessons for mixing video clips with ffmpeg while keeping audio and video in sync.

problem: audio/video desync when mixing clips

what went wrong

using -ss X -t Y to pre-trim input, then applying relative trim filters caused timing drift:

# BAD: relative timestamps after pre-trim
ffmpeg -ss 64 -t 36 -i original.mp4 ...
  -filter_complex "
    [0:v]split=5[orig1][orig2]...;
    [orig1]trim=0:4,setpts=PTS-STARTPTS[o1];
    [orig2]trim=4:11,setpts=PTS-STARTPTS[o2];
    ..."

this produced wrong duration (38s instead of 36s) with audio desync.

solution: use absolute timestamps from full input

trim directly from full original using absolute timestamps:

# GOOD: absolute timestamps from full file
ffmpeg -i original.mp4 -i scene1.mp4 -i scene2.mp4 ...
  -filter_complex "
    [0:v]trim=64:68,setpts=PTS-STARTPTS[o1];
    [1:v]scale=1280:720,trim=4:6,setpts=PTS-STARTPTS[s1];
    [0:v]trim=70:75,setpts=PTS-STARTPTS[o2];
    ...
    [o1][s1][o2]...concat=n=N:v=1:a=0[outv];
    [0:a]atrim=64:100,asetpts=PTS-STARTPTS[outa]
  "
  -map "[outv]" -map "[outa]"

key points

absolute timestamps: trim from full input file, not pre-trimmed
separate audio handling: use atrim on audio stream independently
setpts reset: always use setpts=PTS-STARTPTS after trim to reset timestamps
scale before trim: when mixing different resolutions, scale first then trim
video duration = audio duration: ensure total video segments match audio segment length

example: inserting clips into original

to insert generated clips at specific timestamps while keeping continuous audio:

ffmpeg -y \
  -i original.mp4 \
  -i generated-scene.mp4 \
  -filter_complex "
    [0:v]trim=START1:END1,setpts=PTS-STARTPTS[o1];
    [1:v]scale=1280:720,trim=0:DURATION,setpts=PTS-STARTPTS[s1];
    [0:v]trim=START2:END2,setpts=PTS-STARTPTS[o2];
    [o1][s1][o2]concat=n=3:v=1:a=0[outv];
    [0:a]atrim=AUDIO_START:AUDIO_END,asetpts=PTS-STARTPTS[outa]
  " \
  -map "[outv]" -map "[outa]" \
  -c:v libx264 -preset fast -crf 18 \
  -c:a aac -b:a 192k \
  output.mp4

Read the full file on GitHub · 82 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 82 lines · 54 tokens per session scan A 03f742a522a5

Subscribe to this mod's changes

ffmpeg-mixing is a skill published in the GitHub repository vargHQ/sdk (341 stars, last pushed 6d ago), licensed Apache-2.0. It adds 54 tokens to every session and 825 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Creative and media ai-sdk ai-video elevenlabs flux generative-ai image-to-video

ffmpeg-mixing next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
ffmpeg-mixingvargHQ/sdk	Skill	341	6d ago	Apache-2.0	A	54	Claude Code
kling-aimaciejdzierzek/kling-ai-prompt-generator	Skill	35	2mo ago	MIT	A	89	Claude Code
ai-mediaericrisco/rsc-harness	Skill	503	2d ago	MIT	A	82	Claude Code, Codex
frontend-designOrkas-AI/Orkas-VideoStudio	Skill	344	2d ago	MIT	A	57	Claude Code, Codex
stage-planOrkas-AI/Orkas-VideoStudio	Skill	344	2d ago	MIT	A	0	Claude Code, Codex
gate-controlOrkas-AI/Orkas-VideoStudio	Skill	344	2d ago	MIT	A	81	Claude Code, Codex
stage-editOrkas-AI/Orkas-VideoStudio	Skill	344	2d ago	MIT	A	62	Claude Code, Codex

sdk: Skill for Claude Code