Building Audiobooks

The build process converts your MP3 tracks into a single M4B audiobook file with chapters and metadata.

Starting a Build

Prerequisites

Before building, ensure you have:

• ✅ At least one track added
• ✅ A title set in metadata
• ✅ (Optional) Chapters organized
• ✅ (Optional) Cover art added

Build Steps

1. Click the Build button (hammer icon) in the header
2. Choose the output location and filename
3. Click Save
4. Wait for the encoding process to complete

Build Process

The build happens in several phases:

Phase 1: Analyzing

AudioPie reads information from your source tracks:

• Audio codec and bitrate
• Sample rate
• Duration
• Number of channels

Phase 2: Encoding

Each track is converted to AAC format:

• Default bitrate: 128 kbps (configurable)
• Format: AAC-LC
• Container: M4A

Progress shows as a percentage for each track.

Phase 3: Adding Chapters

Chapter markers are embedded in the file:

• Chapter titles
• Start and end times
• Chapter index

Phase 4: Finalizing

The final M4B is created with:

• All audio concatenated
• Metadata embedded
• Cover art attached
• File extension changed to .m4b

Build Settings

Output Bitrate

Configure in Settings:

Bitrate	Quality	File Size
64 kbps	Good (voice)	~28 MB/hour
96 kbps	Better	~42 MB/hour
128 kbps	Best	~56 MB/hour
192 kbps	Overkill	~84 MB/hour

For audiobooks (voice only), 64-96 kbps is usually sufficient.

Output Location

By default, the file dialog opens to:

• Your configured default output directory, or
• Your home/Documents folder

You can set a default output directory in Settings.

File Naming

The default filename is based on your book title:

Title: "The Great Gatsby"
Default filename: The_Great_Gatsby.m4b

Special characters are replaced with underscores for compatibility.

Build Progress

During the build, a progress modal shows:

┌─────────────────────────────────────────┐
│           Building Audiobook            │
├─────────────────────────────────────────┤
│                                         │
│  [████████████░░░░░░░░░] 60%            │
│                                         │
│  Encoding track 3 of 5...               │
│                                         │
└─────────────────────────────────────────┘

caution

Do not close AudioPie during the build process. This may result in corrupted output.

Build Performance

Build time depends on:

Factor	Impact
Total audio duration	Major
Number of tracks	Minor
Source file quality	Minor
Computer speed	Moderate
FFmpeg threads	Moderate

Typical speeds:

• ~2-5x real-time on modern computers
• 10-hour audiobook: 2-5 minutes to build

Optimizing Build Speed

In Settings, you can configure:

• FFmpeg Threads — More threads = faster encoding (but more CPU usage)
• Recommended: Leave at default (auto) or set to number of CPU cores

Output File

M4B Format

The output is a standard M4B file:

• Based on MPEG-4 container
• AAC audio codec
• Chapter markers (Nero chapters)
• Metadata tags
• Embedded cover art

Compatibility

M4B files work with:

Player	Platform	Support
Apple Books	macOS, iOS	✅ Full
Audiobookshelf	Web, Apps	✅ Full
Smart AudioBook Player	Android	✅ Full
Prologue	iOS	✅ Full
VLC	All	✅ Chapters
Plex	Server	✅ Full

Troubleshooting

Build Fails Immediately

• Check FFmpeg is installed/configured correctly
• Ensure all tracks are valid MP3 files
• Check disk space for output

Build Hangs

• Very long tracks may take time
• Check FFmpeg process in Task Manager
• Try reducing FFmpeg threads in Settings

Output Has No Audio

• Source files may be corrupted
• Try re-encoding source MP3s
• Check FFmpeg error output

Chapters Missing

• Ensure chapters were configured
• Try rebuilding
• Check with ffprobe on the output file

File Too Large

• Reduce output bitrate (64 kbps for voice)
• Ensure you're not using 192+ kbps
• Check source file quality

Player Doesn't Recognize File

• Rename .m4b to .m4a and back
• Re-import into player
• Try a different player to verify file integrity