FFmpeg Audio Processing

benchflow-ai

•

9382423 months ago

Source Raw

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

Quick Install

npxskills add benchflow-ai/skillsbench--skill "FFmpeg Audio Processing"

Instructions

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

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