Audio Processing & Conversion

Intermediatev1.0.0

Process audio with FFmpeg — format conversion, normalization, noise reduction, splitting, merging, and metadata management for podcasts, music, and voice content.

Content

Overview

FFmpeg handles every audio task: format conversion, volume normalization, noise reduction, silence detection, stream extraction, and metadata management. Master these patterns for podcast production, music processing, and voice content workflows.

Why This Matters

-Universal conversion — any audio format to any other
-Normalization — consistent volume across episodes/tracks
-Extraction — pull audio from video files
-Automation — scriptable audio processing pipelines

How It Works

Step 1: Format Conversion

bash

# Convert to MP3 (most compatible)
ffmpeg -i input.wav -c:a libmp3lame -b:a 192k output.mp3

# Convert to AAC (Apple/web)
ffmpeg -i input.wav -c:a aac -b:a 192k output.m4a

# Convert to Opus (smallest, modern)
ffmpeg -i input.wav -c:a libopus -b:a 128k output.opus

# Convert to FLAC (lossless)
ffmpeg -i input.wav -c:a flac output.flac

# Extract audio from video
ffmpeg -i video.mp4 -vn -c:a copy audio.aac    # Copy (no re-encode)
ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3  # Re-encode

Step 2: Volume Normalization

bash

# Two-pass loudness normalization (broadcast standard)
# Pass 1: Analyze
ffmpeg -i input.mp3 -af loudnorm=I=-16:TP=-1.5:LRA=11:print_format=json -f null /dev/null

# Pass 2: Apply (use values from pass 1)
ffmpeg -i input.mp3 \
  -af loudnorm=I=-16:TP=-1.5:LRA=11 \
  -c:a libmp3lame -b:a 192k output.mp3

# Simple volume adjustment
ffmpeg -i input.mp3 -af "volume=1.5" louder.mp3    # 1.5x volume
ffmpeg -i input.mp3 -af "volume=-3dB" quieter.mp3  # Reduce by 3dB

Step 3: Split and Merge

bash

# Split audio at timestamps
ffmpeg -i podcast.mp3 -ss 00:05:00 -to 00:10:00 -c copy segment.mp3

# Merge multiple audio files
# Create file list
echo "file 'intro.mp3'" > list.txt
echo "file 'content.mp3'" >> list.txt
echo "file 'outro.mp3'" >> list.txt

ffmpeg -f concat -safe 0 -i list.txt -c copy merged.mp3

# Add silence between segments
ffmpeg -f lavfi -i anullsrc=r=44100:cl=stereo -t 2 silence.mp3

Step 4: Trim Silence

bash

# Detect silence
ffmpeg -i input.mp3 -af silencedetect=noise=-30dB:d=0.5 -f null /dev/null

# Remove leading/trailing silence
ffmpeg -i input.mp3 \
  -af "silenceremove=start_periods=1:start_duration=0.1:start_threshold=-40dB, \
       areverse,silenceremove=start_periods=1:start_duration=0.1:start_threshold=-40dB, \
       areverse" \
  trimmed.mp3

Best Practices

-Use -c:a copy when only changing container (no quality loss)
-Normalize to -16 LUFS for podcasts, -14 LUFS for music
-Use Opus for modern applications (best quality per bit)
-Use FLAC for archival (lossless, smaller than WAV)
-Always specify sample rate (-ar 44100) for consistent output

Common Mistakes

-Re-encoding when stream copy would work (-c:a copy)
-Not normalizing volume (inconsistent levels between tracks)
-Using MP3 at < 128kbps (audible quality loss)
-Lossy-to-lossy conversion (quality degrades each time)
-Missing metadata in output (-map_metadata 0 to preserve)

FAQ

Discussion

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How It Works

Step 1: Format Conversion

bash

# Convert to MP3 (most compatible)
ffmpeg -i input.wav -c:a libmp3lame -b:a 192k output.mp3

# Convert to AAC (Apple/web)
ffmpeg -i input.wav -c:a aac -b:a 192k output.m4a

# Convert to Opus (smallest, modern)
ffmpeg -i input.wav -c:a libopus -b:a 128k output.opus

# Convert to FLAC (lossless)
ffmpeg -i input.wav -c:a flac output.flac

# Extract audio from video
ffmpeg -i video.mp4 -vn -c:a copy audio.aac    # Copy (no re-encode)
ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3  # Re-encode

Step 2: Volume Normalization

bash

# Two-pass loudness normalization (broadcast standard)
# Pass 1: Analyze
ffmpeg -i input.mp3 -af loudnorm=I=-16:TP=-1.5:LRA=11:print_format=json -f null /dev/null

# Pass 2: Apply (use values from pass 1)
ffmpeg -i input.mp3 \
  -af loudnorm=I=-16:TP=-1.5:LRA=11 \
  -c:a libmp3lame -b:a 192k output.mp3

# Simple volume adjustment
ffmpeg -i input.mp3 -af "volume=1.5" louder.mp3    # 1.5x volume
ffmpeg -i input.mp3 -af "volume=-3dB" quieter.mp3  # Reduce by 3dB

Step 3: Split and Merge

bash

# Split audio at timestamps
ffmpeg -i podcast.mp3 -ss 00:05:00 -to 00:10:00 -c copy segment.mp3

# Merge multiple audio files
# Create file list
echo "file 'intro.mp3'" > list.txt
echo "file 'content.mp3'" >> list.txt
echo "file 'outro.mp3'" >> list.txt

ffmpeg -f concat -safe 0 -i list.txt -c copy merged.mp3

# Add silence between segments
ffmpeg -f lavfi -i anullsrc=r=44100:cl=stereo -t 2 silence.mp3

Step 4: Trim Silence

bash

# Detect silence
ffmpeg -i input.mp3 -af silencedetect=noise=-30dB:d=0.5 -f null /dev/null

# Remove leading/trailing silence
ffmpeg -i input.mp3 \
  -af "silenceremove=start_periods=1:start_duration=0.1:start_threshold=-40dB, \
       areverse,silenceremove=start_periods=1:start_duration=0.1:start_threshold=-40dB, \
       areverse" \
  trimmed.mp3