ffmpeg-audio-processing

Extract, normalize, mix, and process audio tracks - audio manipulation and analysis

Security Scan

The instructions match an FFmpeg audio-processing skill, but the package metadata omits required binaries (ffmpeg / ffprobe) and thus is internally inconsistent; otherwise the skill is instruction-only and low-install-risk.

Purpose & Capability

The name/description and the SKILL.md are consistent: they provide FFmpeg commands to extract, normalize, mix, and analyze audio. However, the metadata declares no required binaries even though the runtime instructions rely on ffmpeg and ffprobe — this omission is an incoherence and should be corrected.

Instruction Scope

SKILL.md contains concrete ffmpeg/ffprobe command examples focused on audio tasks and does not instruct reading unrelated system files, environment variables, or sending data to external endpoints. The commands operate on local media files as expected for this purpose.

Install Mechanism

There is no install spec and no code files; this is an instruction-only skill, so nothing is written to disk by the skill itself. That is the lowest-risk install profile.

Credentials

The skill declares no environment variables or credentials and the instructions do not reference secrets. The lack of declared required binaries (ffmpeg/ffprobe) is the main proportionality issue — the skill implicitly requires local binaries but doesn't state them.

Persistence & Privilege

The skill does not request persistent presence (always is false) and does not instruct modifying agent configuration or other skills. Autonomous invocation is allowed by default but not combined with other privilege red flags.

What to consider before installing

This SKILL.md is a straightforward set of ffmpeg examples and appears to do what it says, but metadata omitted a key detail: the runtime examples require ffmpeg and ffprobe. Before installing or enabling: 1) Confirm the agent environment has trusted ffmpeg/ffprobe binaries (and their versions). 2) Ask the publisher to update metadata to declare these required binaries. 3) Be aware that if the agent executes these commands, it will operate on local files — ensure you trust the skill and restrict which files the agent can access or require explicit approval before running. 4) Because this is instruction-only, there's no installer risk, but you should still audit any automated runs to avoid accidental processing or disclosure of sensitive media.

FFmpeg Audio Processing Skill

Extract, normalize, mix, and process audio tracks from video files.

When to Use

• Extract audio from video
• Normalize audio levels
• Mix multiple audio tracks
• Convert audio formats
• Extract specific channels
• Adjust audio volume

Extract Audio

# Extract as MP3
ffmpeg -i video.mp4 -vn -acodec libmp3lame -q:a 2 audio.mp3

# Extract as AAC (copy, no re-encode)
ffmpeg -i video.mp4 -vn -c:a copy audio.aac

# Extract as WAV (uncompressed)
ffmpeg -i video.mp4 -vn -acodec pcm_s16le audio.wav

# Extract specific audio stream
ffmpeg -i video.mp4 -map 0:a:1 -c:a copy audio2.aac

Normalize Audio

# Normalize loudness (ITU-R BS.1770-4)
ffmpeg -i input.mp4 -af "loudnorm=I=-23:TP=-1.5:LRA=11" output.mp4

# Simple normalization
ffmpeg -i input.mp4 -af "volume=2.0" output.mp4

# Peak normalization
ffmpeg -i input.mp4 -af "volumedetect" -f null -
# Then use the detected peak to normalize
ffmpeg -i input.mp4 -af "volume=0.5" output.mp4

Volume Adjustment

# Increase volume by 6dB
ffmpeg -i input.mp4 -af "volume=6dB" output.mp4

# Decrease volume by 3dB
ffmpeg -i input.mp4 -af "volume=-3dB" output.mp4

# Set absolute volume
ffmpeg -i input.mp4 -af "volume=0.5" output.mp4

Channel Operations

# Extract left channel
ffmpeg -i stereo.mp3 -map_channel 0.0.0 left.mp3

# Extract right channel
ffmpeg -i stereo.mp3 -map_channel 0.0.1 right.mp3

# Convert stereo to mono
ffmpeg -i stereo.mp3 -ac 1 mono.mp3

# Convert mono to stereo
ffmpeg -i mono.mp3 -ac 2 stereo.mp3

Mix Audio Tracks

# Replace audio track
ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -map 0:v:0 -map 1:a:0 output.mp4

# Mix two audio tracks
ffmpeg -i video.mp4 -i audio2.mp3 \
  -filter_complex "[0:a][1:a]amix=inputs=2:duration=first" \
  -c:v copy output.mp4

# Mix with volume control
ffmpeg -i video.mp4 -i bgm.mp3 \
  -filter_complex "[0:a]volume=1.0[voice];[1:a]volume=0.3[music];[voice][music]amix=inputs=2:duration=first" \
  -c:v copy output.mp4

Audio Delay

# Delay audio by 0.5 seconds
ffmpeg -i video.mp4 -itsoffset 0.5 -i video.mp4 \
  -map 0:v -map 1:a -c copy output.mp4

# Using adelay filter (milliseconds)
ffmpeg -i input.mp4 -af "adelay=500|500" output.mp4

Sample Rate Conversion

# Resample to 48kHz
ffmpeg -i input.mp4 -af "aresample=48000" output.mp4

# Resample audio only
ffmpeg -i input.mp4 -vn -af "aresample=48000" -ar 48000 audio.wav

Audio Filters

# High-pass filter (remove low frequencies)
ffmpeg -i input.mp4 -af "highpass=f=200" output.mp4

# Low-pass filter (remove high frequencies)
ffmpeg -i input.mp4 -af "lowpass=f=3000" output.mp4

# Band-pass filter
ffmpeg -i input.mp4 -af "bandpass=f=1000:width_type=h:w=500" output.mp4

# Fade in/out
ffmpeg -i input.mp4 -af "afade=t=in:st=0:d=2,afade=t=out:st=8:d=2" output.mp4

Audio Analysis

# Detect volume levels
ffmpeg -i input.mp4 -af "volumedetect" -f null -

# Measure loudness (LUFS)
ffmpeg -i input.mp4 -af "ebur128=peak=true" -f null -

# Get audio statistics
ffprobe -v error -select_streams a:0 \
  -show_entries stream=sample_rate,channels,bit_rate \
  -of json input.mp4

Combine Multiple Audio Files

# Concatenate audio files
ffmpeg -i "concat:audio1.mp3|audio2.mp3|audio3.mp3" -c copy output.mp3

# Using file list
# file 'audio1.mp3'
# file 'audio2.mp3'
ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp3

Notes

• Use -vn to disable video when extracting audio
• -map to select specific streams
• -af for audio filters
• -ac for channel count
• -ar for sample rate
• Normalization may require two passes for accurate results