FFmpeg Audio Processing

Overview

Reference guide for common ffmpeg audio processing operations including metadata editing, format conversion, sample rate changes, and loudness normalization.

Quick Reference

Task	Key Flag	Example
Read metadata	ffprobe -i	ffprobe -i file.mp3
Set metadata	-metadata	-metadata title="Song"
Copy stream	-c copy	No re-encoding
Format conversion	-c:a	-c:a aac -b:a 192k
Sample rate	-ar	-ar 44100
Volume/norm	-af "volume"	-af "volume=2.0"
LUFS norm	-af "loudnorm"	loudnorm=I=-14:TP=-1.0
Fade in/out	-af "afade"	afade=t=in:st=0:d=2
Trim audio	-af "atrim"	atrim=0:30,asetpts=PTS-STARTPTS

Metadata Reference

MP3 (ID3v2.3) - Recommended for Maximum Compatibility

Important: When tagging MP3 files, strongly recommend forcing ID3v2.3 version for maximum device and platform compatibility.

# Add -id3v2_version 3 to force ID3v2.3
ffmpeg -i input.mp3 -c copy -id3v2_version 3 \
  -metadata title="Title" \
  -metadata artist="Artist" \
  output.mp3

Metadata Field	Description	Example
title	Song title	-metadata title="My Song"
artist	Artist/performer	-metadata artist="John Doe"
album	Album name	-metadata album="My Album"
year	Year (4 digits)	-metadata year="2024"
track	Track number	-metadata track="1" or "1/12"
disc	Disc number	-metadata disc="1" or "1/2"
genre	Genre	-metadata genre="Rock"
composer	Composer	-metadata composer="Beethoven"
lyricist	Lyricist	-metadata lyricist="Lyricist Name"
conductor	Conductor	-metadata conductor="Conductor Name"
album_artist	Album artist (use Various Artists for compilations)	-metadata album_artist="Various Artists"
grouping	Grouping/Series	-metadata grouping="Greatest Hits"
comment	Comment	-metadata comment="My comment"
isrc	ISRC code	-metadata isrc="USRC17607839"
copyright	Copyright info	-metadata copyright="© 2024 Label"
encoder	Encoding tool	-metadata encoder="FFmpeg"
bpm	Beats per minute	-metadata bpm="120"
key	Musical key	-metadata key="C" or "Dm"
mood	Mood	-metadata mood="Happy"
language	Language (ISO 639-2)	-metadata language="eng"

M4A/AAC (MP4 Metadata)

Metadata Field	Description	Example
title	Song title	-metadata title="My Song"
artist	Artist	-metadata artist="John Doe"
album	Album name	-metadata album="My Album"
year	Year	-metadata year="2024"
track	Track number (format: track/total)	-metadata track="1/12"
disc	Disc number	-metadata disc="1/2"
genre	Genre	-metadata genre="Rock"
composer	Composer	-metadata composer="Beethoven"
album_artist	Album artist	-metadata album_artist="Various Artists"
bpm	BPM (integer)	-metadata bpm="120"
gapless	Gapless playback flag	-metadata gapless="1"

FLAC (Vorbis Comments)

Metadata Field	Description	Example
title	Song title	-metadata title="My Song"
artist	Artist	-metadata artist="John Doe"
album	Album name	-metadata album="My Album"
date	Date (YYYY-MM-DD)	-metadata date="2024-01-01"
tracknumber	Track number	-metadata tracknumber="1"
discnumber	Disc number	-metadata discnumber="1"
genre	Genre	-metadata genre="Rock"
composer	Composer	-metadata composer="Beethoven"
lyricist	Lyricist	-metadata lyricist="Lyricist Name"
conductor	Conductor	-metadata conductor="Conductor Name"
albumartist	Album artist	-metadata albumartist="Various Artists"
grouping	Grouping/Series	-metadata grouping="Greatest Hits"
comment	Comment	-metadata comment="My comment"
isrc	ISRC code	-metadata isrc="USRC17607839"
copyright	Copyright	-metadata copyright="© 2024 Label"
encoder	Encoding tool	-metadata encoder="FFmpeg"
replaygain_track_gain	ReplayGain track gain	-metadata replaygain_track_gain="-2.5 dB"
replaygain_album_gain	ReplayGain album gain	-metadata replaygain_album_gain="-1.8 dB"

Basic Operations

Reading Metadata

Basic info (all formats):

# Quick overview
ffprobe -i audio.mp3

# Show format and stream info
ffprobe -i audio.mp3 -show_format -show_streams

Read metadata only:

# MP3/M4A/FLAC - show all metadata tags
ffprobe -i audio.mp3 -show_entries format_tags

# Show specific metadata fields
ffprobe -i audio.mp3 -show_entries format_tags=title,artist,album

# Output as JSON
ffprobe -i audio.mp3 -show_entries format_tags -print_format json

# Output as flat key=value
ffprobe -i audio.mp3 -show_entries format_tags -of default=noprint_wrappers=1

Extract specific metadata value (for scripting):

# Get title
ffprobe -i audio.mp3 -show_entries format_tags=title -of default=noprint_wrappers=1:nokey=1 2>/dev/null

# Get artist
ffprobe -i audio.mp3 -show_entries format_tags=artist -of default=noprint_wrappers=1:nokey=1 2>/dev/null

# Get BPM (works if present)
ffprobe -i audio.mp3 -show_entries format_tags=bpm -of default=noprint_wrappers=1:nokey=1 2>/dev/null

Show audio properties:

# Codec, sample rate, bitrate
ffprobe -i audio.mp3 -show_entries stream=codec_name,sample_rate,channels,bit_rate -of default=noprint_wrappers=1

# Duration and file size
ffprobe -i audio.mp3 -show_entries format=duration,size -of default=noprint_wrappers=1

Metadata Modification

MP3 (force ID3v2.3 for maximum compatibility):

# Modify MP3 metadata - force ID3v2.3
ffmpeg -i input.mp3 -c copy -id3v2_version 3 \
  -metadata title="My Song" \
  -metadata artist="John Doe" \
  -metadata album="My Album" \
  -metadata year="2024" \
  -metadata genre="Rock" \
  -metadata track="1/12" \
  output.mp3

M4A/AAC:

# Modify M4A metadata
ffmpeg -i input.m4a -c copy \
  -metadata title="My Song" \
  -metadata artist="John Doe" \
  -metadata album="My Album" \
  -metadata track="1/12" \
  output.m4a

FLAC:

# Modify FLAC metadata
ffmpeg -i input.flac -c copy \
  -metadata title="My Song" \
  -metadata artist="John Doe" \
  -metadata album="My Album" \
  -metadata date="2024-01-01" \
  -metadata tracknumber="1" \
  output.flac

Add Album Art

MP3 with album art (force ID3v2.3):

ffmpeg -i audio.mp3 -i cover.jpg -map 0:a -map 1:v \
  -c:a copy -c:v mjpeg -id3v2_version 3 \
  -metadata title="Song Title" \
  -metadata artist="Artist Name" \
  output.mp3

M4A with album art:

ffmpeg -i audio.m4a -i cover.jpg -map 0:a -map 1:v \
  -c:a copy -c:v png \
  output.m4a

FLAC with album art:

ffmpeg -i audio.flac -i cover.jpg -map 0:a -map 1:v \
  -c:a copy -c:v png \
  output.flac

Remove All Metadata

# MP3 - remove all metadata
ffmpeg -i input.mp3 -c copy -map_metadata -1 output.mp3

# Or remove specific fields only
ffmpeg -i input.mp3 -c copy \
  -metadata title="" \
  -metadata artist="" \
  output.mp3

Format Conversion

# WAV to AAC (192kbps)
ffmpeg -i audio.wav -c:a aac -b:a 192k output.aac

# WAV to MP3 (320kbps)
ffmpeg -i audio.wav -c:a libmp3lame -b:a 320k output.mp3

# FLAC to MP3
ffmpeg -i audio.flac -c:a libmp3lame -q:a 2 output.mp3

Sample Rate Conversion

# 48kHz to 44.1kHz (CD format)
ffmpeg -i input.wav -ar 44100 output.wav

# With high-quality resampling
ffmpeg -i input.wav -af "aresample=resampler=soxr_vhq" -ar 44100 output.wav

Advanced Operations

LUFS Normalization (Streaming Standard)

# Single pass (good for most cases)
ffmpeg -i input.wav -af "loudnorm=I=-14:TP=-1.0:LRA=11" \
  -ar 44100 output.wav

Parameters:

• I=-14 — Target integrated loudness (-14 LUFS for Spotify, Apple Music, YouTube)
• TP=-1.0 — True peak ceiling (-1 dBTP)
• LRA=11 — Loudness range target

Bit Depth Conversion with Dithering

# 24-bit to 16-bit (dither filter requires ffmpeg with libsoxr)
ffmpeg -i 24bit.wav \
  -af "aformat=sample_fmts=s16,dither=scale=16:noise_shape=triangular_hp" \
  -acodec pcm_s16le 16bit.wav

Without dither filter (alternative):

ffmpeg -i 24bit.wav -af "aformat=sample_fmts=s16" -acodec pcm_s16le 16bit.wav

Dither types: shibata (best for music), triangular_hp (standard), rectangular (basic)

Note: The dither filter requires ffmpeg compiled with libsoxr. If you get "Filter not found" error, use the alternative command above.

Trim and Fade

# First 30 seconds with fade in/out
ffmpeg -i input.wav \
  -af "atrim=0:30,asetpts=PTS-STARTPTS,afade=t=in:st=0:d=2,afade=t=out:st=27:d=3" \
  output.wav

Multi-Output from Single Source

ffmpeg -i master.wav \
  -filter_complex "[0:a]loudnorm=I=-14[norm];[0:a]atrim=0:30,asetpts=PTS-STARTPTS[preview]" \
  -map "[norm]" -c:a:0 pcm_s16le spotify-master.wav \
  -map "[preview]" -c:a:1 libmp3lame -b:a 192k preview.mp3

Common Mistakes

Mistake	Fix
Forgetting -c copy when only editing metadata	Causes unnecessary re-encoding
Using -ar without considering bit depth	Use aformat filter for bit depth changes
Single-pass loudnorm for batch processing	Use two-pass for consistent loudness across tracks
Missing asetpts=PTS-STARTPTS after atrim	Causes timestamp issues
Not forcing ID3v2.3 for MP3	Some devices don't support ID3v2.4

Related Tools

• ffprobe — Inspect audio file properties and metadata

  # Full info dump
  ffprobe -i file.mp3
  
  # Metadata only (JSON)
  ffprobe -i file.mp3 -show_entries format_tags -print_format json
  
  # Audio properties
  ffprobe -i file.mp3 -show_entries stream=codec_name,sample_rate,channels,bit_rate
  

• MusicBrainz Picard — Automatic metadata tagging
• ReplayGain — Alternative loudness standard