Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/varghq/sdk/ffmpeg-mixingnpx skills add vargHQ/sdk --skill ffmpeg-mixinggit clone --depth 1 https://github.com/vargHQ/sdkWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/varghq/sdk/ffmpeg-mixing)<a href="https://agentmods.dev/skills/varghq/sdk/ffmpeg-mixing"><img src="https://agentmods.dev/badge/skills/varghq/sdk/ffmpeg-mixing.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00027 | $0.00413 |
| Sonnet 5 | $0.00011 | $0.00165 |
| Haiku 4.5 | $0.00005 | $0.00082 |
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 6d 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.
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
atrimon audio stream independently - setpts reset: always use
setpts=PTS-STARTPTSafter 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
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.
- 6d ago First seen · 82 lines · 54 tokens per session scan A 03f742a522a5
ffmpeg-mixing is a skill published in the GitHub repository vargHQ/sdk (336 stars, last pushed 4d ago), licensed Apache-2.0. It adds 54 tokens to every session and 825 once invoked, about $0.0003 per session on Opus 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.
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